ORTHOPEDIC MCQS OB 20 BASIC 3

52. A type IV (delayed-type hypersensitivity reaction) can be seen in which of the following scenarios?

1. Packed red blood cell transfusion
2. Platelet transfusion
3. Immune inert scaffold placement
4. Metal plate and screw placement for fracture
5. Red man syndrome from vancomycin administration

 

Corrent answer: 4

 

A type IV, or delayed-type hypersensitivity reaction, can be seen with placement of orthopedic hardware.

 

Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop. Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.

 

Hallab et al note that a triple assay is more sensitive than a single assay, and may have a role in future investigation in this arena. They mention that no true gold standard has been established for workup of these patients in regards to possible metal sensitivities.

 

53. All of the following are true of BMP-3 EXCEPT?

 

1. It antagonizes the activity of BMP-2
2. It is the most abundant BMP in demineralized bone matrix
3. Knockout mice have twice as much trabecular bone as controls
4. It is osteoinductive
5. It increases levels of chondrogenic markers like Type II collagen and aggregcan

 

Corrent answer: 4

 

Bone morphogenetic proteins (BMPs) belong to a subgroup of proteins within the transforming growth factor beta (TGF-B) superfamily. There are nearly 30 different

members of the BMP family. The osteogenic effects of BMPs 2 and 7 have been well documented. The cellular effect of many of the remaining BMPs continue to be evaluated.

 

Bahamonde and Lyons showed that BMP-3 antagonizes the activity of BMP-2. They also showed that BMP-3 is the most abundant BMP in demineralized bone matrix.

 

Daluiski et al also showed that BMP-3 antagonizes BMP-2, and that BMP-3 knockout mice have twice as much trabecular bone as controls.

 

Cheng et al showed in tissue culture models that BMP-2, 4, 6, 7, and 9 were osteogenic. BMP-3 was shown to increase levels of chondrogenic markers like Type II collagen and aggregcan.

 

54. An orthopaedic surgeon wishes to initiate advertising in a local newspaper to increase awareness of the medical services he provides. Which of the following can be used without being at risk of being deemed unfair, false, misleading or deceptive and subject to heavy penalties by the Federal Trade Commission?

 

1. "Bloodless arthroscopic surgery"
2. "Board Certified in Joint Replacement Surgery"
3. "New carpal tunnel release with relatively little pain"
4. "Injections to Cure Your Arthritis"
5. "Patients can return to all sports activity following joint replacement surgery"

 

Corrent answer: 3

 

Phrases such as "does not cause pain" are misleading and deceptive, however these can be qualified (e.g., "relatively little pain") to more accurately convey the more typical patient experience and is appropriate to use in advertising.

 

The article by Capozzi reviews several dubious advertising phrases and states the United States Federal Trade Commission Act prohibits organizations such as the American Medical Association (AMA) or the American Academy of Orthopaedic Surgeons (AAOS) from placing restrictions on physicians who advertise. Physicians who advertise in a deceptive manner may be subject to sanctions from state consumer protection agencies, the AAOS, the Federal Trade Commission, and state medical licensing boards.

 

Incorrect Answers:

Answer 1: To call a procedure "bloodless" implies that there is no blood lost during or after the surgery. There may be relatively little blood lost with

certain procedures, but there is almost always some measurable loss of blood. Answer 2: there is no "board certification" in existence for joint replacement surgery and thus the advertised credential is false.

Answer 4: the term "cure" should be utilized only if it an accurate description of the degree of relief experienced by the majority of patients and to date there is no available viscosupplementation to "cure" arthritis.

Answer 5: avoiding high-impact activity is the accepted standard recommendation after joint replacement surgery. To advertise that all forms of sports activity are acceptable, encouraged, or expected misrepresents the

risks associated with such behavior.

 

55. A 65-year-old man sustains the reverse obliquity intertrochanteric fracture as shown in Figure A. He undergoes fixation with a sliding hip screw construct and his 3 month postoperative radiograph is shown in Figure B. His treating surgeon states that the "standard of care was performed for his fracture pattern" and the patient asks you as a consulting surgeon for a second opinion. Each of the following statements regarding your legal and ethical obligations as the consulting surgeon providing a second opinion are true EXCEPT?

 

1. Second-opinion physicians have an ethical obligation to discuss the standard of care for reverse obliquity hip fractures
2. Second-opinion physicians have a legal obligation to become an expert

witness for the patient/plaintiff in a negligence lawsuit against the treating physician

3. Many states have mandatory or voluntary medical-error reporting systems that the consulting surgeon is ethically mandated to utilize
4. Second-opinion physicians do not have a legal obligation to disclose errors made by other physicians
5. It is a fundamental ethical requirement that a physician should at all times deal honestly and openly with patients

 

Corrent answer: 2

 

This patient has a reverse obliquity intertrochanteric hip fracture that was treated with a sliding hip screw construct. It has been shown in the literature that this construct is fraught with complications for this particular fracture pattern.

 

The article by Bhattacharyya recounts a case of using a semitubular plate construct for a both forearm fracture fixation. The article highlights the AMA Code of Medical Ethics which states that consulting physicians have an ethical but not legal obligation to disclose breaches in the standard of care.

 

The article by Hebert highlights the importance of honest discussions with patients and offers tips for disclosure of medical errors. There is no legal obligation for second opinion physicians to testify against the treating physician, however he or she is subject to discovery, deposition, and subpoena as a result of being involved in the patient's care.

56. Vaughn-Jackson syndrome in rheumatoid arthritis is best described as?

 

1. Cranial migration of the dens from soft tissue erosion and bone loss between occiput and C1&C2
2. Rupture of flexor pollicis longus in the carpal tunnel
3. Synovitis in the DRUJ leading to supination of the carpal bones away from the head of the ulna
4. Rupture of the hand digital extensor tendons
5. Synovitis of the MTP joints with eventual hyperextension deformity of the MTP

 

Corrent answer: 4

Vaughn-Jackson syndrome describes the rupture of the hand digital extensor tendons, which start on the ulnar side of the wrist first and then move radially. This is thought to occur from DRUJ instability, resulting in dorsal prominence

of the ulnar head, leading to an attritional rupture of the extensor tendons. Extensor digiti minimi is the extensor tendon commmonly ruptured.

 

Vaughn-Jackson first described the condition in his case report in JBJS in 1948.

 

Williamson et al. report on Vaughn-Jackson syndrome, and note that prevention is the best method of treatment of this finding. They note that consideration of the surrounding arthritic changes must be taken into account when treating chronic dorsal tendon attrition.

 

Incorrect Answers:

1. Cranial migration of dens from soft tissue erosion and bone loss between occiput and C1&C2 describes basilar invagination.
2. Rupture of flexor pollicis longus in the carpal tunnel describes Mannerfelt syndrome.
3. Synovitis in the DRUJ leading to supination of the carpal bones away from the head of the ulna describes Caput-ulna syndrome.

5) Synovitis of the MTP joints with eventual hyperextension deformity of the MTP is a common toe deformity seen with RA.

 

206. Genetic polymorphisms in all of the following genes are associated with osteoporosis EXCEPT?

 

1. Calcitonin receptor
2. Estrogen receptor-1
3. Vitamin D receptor
4. Type I collagen alpha-1 chain
5. Cartilage oligomeric matrix protein (COMP)

Corrent answer: 5

Polymorphisms in the genes for the calcitonin receptor, estrogen receptor-1, vitamin D receptor, and the type I collagen alpha-1 chain (along with over 45 other genes) have been shown to be associated with osteoporosis. Answer 5, Cartilage oligomeric matrix protein, shows no current association with osteoporosis, but is the known genetic mutation associated with multiple epiphyseal dysplasia (a frequently tested fact). No single cause for osteoporosis has been shown at this point in time.

Jin et al conducted a meta-analysis regarding polymorphisms in the 5' flank of COL1A1 gene and the conflicting results relating to osteoporosis. They found that the COL1A1 Sp1 polymorphism is associated with a modest reduction in BMD and an increased risk of fracture.

 

The attached review by Huang and Kung discusses the multiple genetic and environmental determinants of osteoporosis and illustration A (from a different review by these same authors) lists the known genes currently associated with osteoporosis.

 

207. The greatest biomechanical difference between unicortical and bicortical locking screws is seen when what force is applied?

 

1. Compression
2. Torsion
3. Distraction
4. Bending on the side of the plate
5. Bending on the surface perpendicular to the plate

 

Corrent answer: 2

 

Torsion force has the largest biomechanical difference between unicortical locked screws and bicortical locked screws.

 

The first referenced article by Roberts et al noted that by replacing the farthest unicortical

screws (3 per side of the fracture) with bicortical locking screws, torsion resistance was increased by over 50%.

 

The second referenced article by Fulkerson et al noted decreased resistance to all applied forces with unicortical screws in a comminuted fracture model, and recommended against their use in such a fracture.

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208. You are planning surgery on a 54-year-old female with the tibial plateau fracture seen in figures A and B. After reduction of the joint surface you plan to fill the void with a bone-graft substitute to prevent joint collapse. Which of the following bone-graft substitutes

disappears most quickly in vivo?

 

1. Collagen-based matrices
2. Calcium phosphate
3. Calcium sulfate
4. Synthetic calcium sulfate and tri-phosphate mixture
5. Coraline hydroxyapatite

 

Corrent answer: 3

Calcium sulfate disappears in vivo quickly, usually within 4-12 weeks. Calcium phosphate and coraline hydroxyapatite are resorbed slowly, somewhere between 1-10 years, depending on the manufacturer. Synthetics that combine calcium sulfate and phosphate

resorb quicker than calcium phosphate but slower than calcium sulfate. Collagen-based matrices show quick resorption of the collegen but slow resorption of their hydroxyapatite coating. Walsh et al. examined the in vivo response of calcium sulfate pellets alone or in combination with autogenous bone graft in a sheep model. They found excellent bone formation in defects filled with calcium sulfate pellets. Immunostaining for various cytokines (BMP-2, BMP-7, PDGF, or TGF-beta)

showed elevated levels in the newly formed bone. They proposed that the local environment acidity was responsible for breakdown of the calcium sulfate. Watson evaluated 8 patients with comminuted tibial metaphyseal fractures treated with an injectable calcium sulfate. They found that bone regrowth was observed in all patients and the bone substitute almost completely resorbed by

3. months. Bucholz reviewed the biochemical, biomechanical, and longevity characteristics of the common bone substitutes.

 

209. Which of the following Figures shows a fixation construct achieving absolute stability?

 

1. Figure A
2. Figure B
3. Figure C
4. Figure D
5. Figure E

 

Corrent answer: 4

 

Figure A shows percutaneous pinning, Figure B shows locked bridge plating, Figure C shows intramedullary nailing, Figure D shows lag fixation and neutralization plating, and Figure E shows external fixation. All except Figure D show relative stability constructs.

 

Absolute stability is a construct seen in Figure D, where lag screws and a neutralization plate are shown in a postoperative clavicle. No micromotion is seen with this technique, and healing is by primary (Haversian) healing, as opposed to the other four constructs, which have relative stability and heal via callus formation. The first reference, the AO Principles textbook, covers this in depth.

 

The second reference by Claes et al notes that bone can still heal with bone (as opposed to fibrous union) with strain rates up to 15%.

210. Which immunoglobulin subtype does the rheumatoid factor target?

1. IgA
2. IgE
3. IgM
4. IgG
5. Rheumatoid factor does not target an immunoglobulin

 

Corrent answer: 4

 

Rheumatoid factor is an auto-antibody most commonly seen with rheumatoid arthritis. The presence of rheumatoid factor can also indicate generalized autoimmune activity unrelated to rheumatoid arthritis (e.g. tissue or organ rejection). Rheumatoid factor is itself an IgM antibody that is directed against the Fc portion of IgG antibody. Rheumatoid factor (IgM) attaches to IgG to form immune complexes which are deposited in tissues like the kidney and contribute to the overall disease process in rheumatoid arthritis.

 

James et al. assessed the occurrence and predictive factors for orthopaedic surgery in an cohort of patients with rheumatoid arthritis. Risk factors for surgery varied but the authors found that decreased inflammatory markers during the first year after diagnosis decreased the risk for subsequent surgery.

 

211. The positive predictive value is defined as which of the following?

 

1. True positives / (true positives + true negatives)
2. False negatives / (false negatives + true positives)
3. False positives / (false positives + false negatives)
4. (True positives + false positives) / (true negatives + false negatives)
5. True positives / (true positives + false positives) Corrent answer: 5

The positive predictive value is defined as the true positives divided by the sum of the positive results (true positive and false positive). It is also defined as the probability that a patient with a positive test actually has the disease; it is dependent on prevalence of disease.

 

The referenced articles by Wojtys and Kuhn et al are two of a series of medical statistics review papers.

 

212. An 85-year-old woman undergoes the treatment seen in Figure A for a displaced left femoral neck fracture. During wound closure, the patient becomes hypoxic and hypotensive. Despite aggressive resuscitation efforts, she passes away three hours later in the intensive care unit. The autopsy findings seen in

Figure B from the patient's lungs are most likely the result of which of the following

 

1. Reaming for the femoral component
2. Insertion of a femoral component after cement pressurization
3. Utilization of undersized broaches during canal preparation
4. Inadequate beta blockade
5. Use of spinal anesthesia

 

Corrent answer: 2

The clinical scenario is consistent with fat emboli syndrome. Figure A, shows a cemented bipolar hemiarthroplasty while Figure B shows marrow embolization into the lungs.

Studies have shown that intramedullary pressure and fat embolization are greatest during pressurization of cement and implant insertion.

 

Intramedullary pressure is influenced by size, shape, sharpness and insertion rate of an implant. Pressurization during cementing of a femoral component generates a large degree of pressure over a much wider surface area than in the other methods described of femoral canal instrumentation or preparation, as the entire femoral canal is

pressurized at one time. This results in the highest degree of marrow embolization to the lungs resulting in hypoxia.

 

Dobrjanski et al studied which variables affected intramedullary pressurization and found that lower implant insertion speed, lower hammering force, a

rubber- compared with steel-tipped hammer and a larger synthetic bone-to- implant radial gap reduced intramedullary pressure generated in a femur module.

 

213. Sustained compression applied to a growth plate under experimental conditions has what effect?

 

1. No effect
2. Accelerated longitudinal growth
3. Decelerated longitudinal growth
4. Decelerated apposition growth
5. Decreased bending strength of the bone

 

Corrent answer: 3

 

The Heuter-Volkmann Law states that compression across the growth plate slows longitudinal growth.

 

Stokes et al demonstrated that sustained compression across the growth plate can decrease longitudinal growth by 40%. Tension across the physis increases growth, but to a lesser degree.

 

214. A 13-year-old girl with a displaced proximal tibia fracture is brought into the emergency department by her adult cousin. The

fracture needs surgical management. The child is living with her cousin's family while her parents are in Germany. While the child speaks fluent English, her cousin and her parents are German-only speaking. How should you consent this patient?

 

1. No consent is needed given the urgent nature of the injury, proceed with surgery
2. Talk with the cousin, using the child as a translator
3. Talk with the cousin, using a German-translator
4. Call the parents in Germany, using the child as a translator over the phone
5. Call the parents in Germany, using a German-translator over the phone

 

Corrent answer: 5

 

This is an urgent (not emergent) clinical senario, and as such, the child needs to have

formal consent by speaking with her parents using a German- translator.

 

Wenger and Lieberman discuss the problems and potential solutions surrounding the process of informed consent in patients who either personally lack capacity to make decisions or in patients who require surrogates (like minors) to make treatment decisions.

 

Lindseth reviews the ethical issues encountered in pediatric orthopaedics and the problems associated with these decisions. Specifically pediatric consent is confounded because the person giving the consent is not the person who will bear the consequences of the treatment.

 

215. What is the primary mode of bisphosphonate excretion?

 

1. Renal
2. Gastrointestinal
3. Liver
4. Skin
5. Pulmonary

 

Corrent answer: 1

 

Bisphosphonates are a broad class of medicines used to treat osteoporosis and Paget's disease. They work by inhibiting osteoclast-mediated resorption after being absorbed into the inorganic phase of bone and taken up by osteoclasts. The paper by Lin et al provides a nice review of bisphosphonates and describe their appropriate use in enhancing bone density in patients with structurally

flawed bone. They describe the mechanism of action of bisphosphonates as pyrophosphate analogues and their renal mechanism of excretion, thus, prohibiting their use in patients with renal insufficiency. Rosier discusses the role of the orthopaedic surgeon in the diagnosis and treatment of patients with osteoporosis, now referred to as the "own the bone" initiative. Central to the treatment of osteoporosis are bisphosphonates and the anti-RANKL

monoclonal antibody, Denosumab.

 

216. The 2009 AAOS Clinical Guideline on prevention of pulmonary embolism in patients undergoing total hip or knee arthroplasty recommends classifying patients as having either a "standard" or "elevated" risk of bleeding complications. The presence of all of the following qualify a patient as having an "elevated" risk of major bleeding EXCEPT?

 

1. History of hemophilia
2. History of protein C deficiency
3. History of a recent gastrointestinal bleed
4. History of a recent hemorrhagic stroke
5. History of Von Willebrand's Disease

 

Corrent answer: 2

 

The 2009 AAOS Clinical Guideline on prevention of pulmonary embolism in patients undergoing total hip or knee arthroplasty recommends that all patients pre-operatively should be classified as either having an elevated or standard risk of bleeding and either an elevated or standard risk of pulmonary embolism.

 

A history of a bleeding disorder (e.g., hemophilia, Von Willebrand's Disease), recent GI bleed, or hemorrhagic stroke qualifies a patient as having an elevated risk of major bleeding.

 

A history of hypercoagulable state (such as protein C deficiency) or previous documented pulmonary embolism qualifies a patient as having an elevated risk of pulmonary embolism. Type of thromboembolism prophylaxis is recommended by weighing risk of major bleeding vs risk of PE. For those patients with a known contraindication to anticoagulation an IVC filter is considered. Mechanical prophylaxis is recommended across all risk (low to

high risk of either bleeding or pulmonary embolism) groups undergoing total hip or total knee arthroplasty. The detailed AAOS guidelines can be found on the AAOS website.

The evidence based clinical recommendations are presented in the reference by Johanson et al.

 

217. In consideration of a prosthetic knee, each of the following are advantages of choosing a polycentric knee with fluid control over a constant friction knee EXCEPT:

 

1. Allows variations in cadence
2. Flexes in a more controlled manner
3. Lighter in weight
4. Improved stance control allows less energy expenditure
5. Overall length of the limb is shortened during initiation of a step reducing the risk of stumbling

 

Corrent answer: 3

 

Single axis, constant friction knees function as a simple hinge. They are light, durable, and much cheaper prostheses making them ideal for growing children who will need multiple prostheses before reaching adulthood. This prosthesis allows only a single speed of walking, and relies solely on alignment for stance phase stability. Polycentric knees offer each of the advantages stated above making it a more ideal prosthesis for the active adult. Disadvantages of the polycentric knee include cost, weight, and more sophisticated maintenance.

 

Tang et al reviews the current prosthetic options for leg and foot amputees. Illustration A demonstrates a single axis knee prosthesis.

Illustration B demonstrates a polycentric knee prosthesis.

 

218. Which of the following biologic agents commonly used to treat rheumatoid arthritis (RA) DOES NOT target tumor necrosis factor- alpha (TNF-alpha)?

1. Infliximab
2. Rituximab
3. Etanercept
4. Golimumab
5. Adalimumab

 

Corrent answer: 2

 

Rituximab is a chimeric monoclonal antibody against the protein CD20, which is primarily found on the surface of immune system B cells. Rituximab is used in combination with methotrexate to treat RA that has not responded to one or more types of treatment, including anti-tumor necrosis factor (TNF) blockers.

 

In rheumatoid arthritis, and other chronic inflammatory conditions, cytokines produced by activated T-cells/macrophages contribute to the pro-inflammatory state. TNF-alpha is thought to be one of the major cytokines involved in rheumatoid arthritis pathology. As a result, many biologic agents used to treat RA are directed towards blocking TNF-alpha or its receptors. These drugs are able to reduce inflammation and stop disease progression.

 

Elliot et al. evaluated the safety and efficacy of infliximab in 20 patients with active RA in an open phase I/II trial lasting 8 weeks. They found that treatment with anti-TNFa was safe, well tolerated and resulted in significant clinical and laboratory improvements.

 

Illustration A depicts five commonly used anti-TNF alpha biologic agents for the treatment of rheumatoid arhtirits with their usual dosing regimens.

 

Incorrect Answers:

Answer 1, 3-5: All of these biologic agents target TNF-alpha

 

219. Receptor activator of nuclear-factor kappa-B ligand (RANKL) is

an important regulator of bone resorption. Which of the following cells is the MAJOR source of RANKL in bone remodelling?

 

1. Osteoclasts
2. Osteoblasts
3. Integrins
4. T cells
5. Macrophages

 

Corrent answer: 2

 

RANKL, a key osteoclastogenic protein, is expressed by osteoblasts and binds to the RANK receptor on osteoclast precursor cells.

 

The binding of RANKL to RANK on osteoclast precursor cells drives their differentiation into mature osteoclasts (multinucleated giant cells). Mature osteoclasts bind to the bone surfaces via integrins and resorb bone via their ruffled border within Howship's lacunae. Osteocytes orchestrate bone resorption and bone deposition by controlling osteoclast and osteoblast activity. Osteoblasts release RANKL to induce osteoclast differentiation, while

osteoblasts release osteoprotegerin (OPG) to downregulate osteoclastogenesis. Osteocytes also release fibroblast growth factor-23 (FGF-23), BMPs and sclerostin to regulate osteoblast activity. Antibodies to RANKL and Sclerostin have both been shown to increase bone density.

 

Compton et al. reviewed osteocyte function and the emerging importance of sclerostin, which is a glycoprotein. Sclerostin is predominantly secreted by osteocytes under physiologic conditions to act as an important negative regulator of bone mass through inhibition of bone formation by osteoblasts.

 

Illustration A demonstrates local bone milieu. It depicts the interplay between osteocytes, osteoblasts, and osteoclasts via the factors described above.

 

Incorrect answers:

Answer 1: RANKL is not expressed by osteoclasts, its expression leads to osteoclast differentiation and activation.

Answer 3: Integrins are transmembrane receptors that allow mature osteoclasts to bind to the surface of bones. They do not express RANKL. Answer 4: RANKL is expressed by T helper cells and is thought to be involved in dendritic cell maturation.

Answer 5: RANKL is not known to be expressed by macrophages.

 

220. A 45-year-old woman with rheumatoid arthritis is being scheduled for a total knee athroplasty in 2 weeks. She is currently taking sulfasalazine, Penicillamine, and etanercept, a tumor necrosis factor inhibitor (aTNF-a). What changes should be made to her medication regimen prior to surgery?

 

1. Discontinuation of all three medications 1 weeks prior to surgery
2. Discontinuation of sulfasalazine 1 weeks prior to surgery, continuation of etanercept and penicillamine
3. Continuation of sulfasalazine, penicillamine, and etanercept
4. Continuation of sulfasalazine and penicillamine, discontinuation of etanercept 1 week prior to surgery
5. Continuation of penicillamine, discontinuation of sulfasalazine and etanercept 1 week prior to surgery

 

Corrent answer: 4

 

Anticytokine disease-modifying antirheumatic drugs (DMARD) have become increasingly popular in the treatment of RA. Immunosuppression and the risk of infection are potential complications for all anti-TNF-alpha medications. Current recommendations for cessation of immunosuppressive therapy are when the drug concentrations are at their lowest levels which include the following: 3 days after etanercept injection; 2 weeks prior to infliximab infusion; 10 days after adalimumab injection. Medications such as sulfasalazine and penicillamine may be continued during the pre and post- operative period. Recent evidence and guidelines such as those reviewed by Keith's paper, suggest that anti-TNF-alpha medications should be stopped 4 weeks prior to surgery.

Giles et al report in their case control series an increased infection rate of RA patients undergoing an orthopaedic procedure who were on TNF-a inhibitors as opposed to patients on more traditional treatment regimens like methotrexate and prednisone.

221. Which of the following supplements affects blood clotting through its effect on platelets?

 

1. Ginkgo
2. Vitamin D
3. Ephedra
4. St. John's Wort
5. Selenium

 

Corrent answer: 1

 

Ginkgo and ginseng are two common supplements used in the general population that have inhibitory effects of platelet function. Adverse peri- operative complications consisting of increased bleeding and hematoma formation have been reported with the use of these two herbal supplements. The most commonly used supplements that could have an effect in the peri- operative period include echinacea, ephedra, garlic, ginkgo, ginseng, kava, St John's wort, and valerian. Bleeding has been shown to be effected by garlic, ginkgo, and ginseng; cardiovascular instability from ephedra; and hypoglycemia from ginseng. Kava and valerian have pharmacodynamic herb- drug interactions that can increase the sedative effect of anesthetics. St John's wort has been shown to alter the metabolism of certain drugs used in the perioperative period.

 

Ang-Lee et al review common supplements used today and their potential anesthesia/operative effects. The article places emphasis on proper history taking of not only medications but also supplements which is often times left out of documentation.

 

222. The femur radiograph of a healthy 25-year-old female is compared to the femur radiograph of a healthy 85-year-old female. Which of the following best describes the 25-year-old's femur?

1. Increased cortical thickness and a smaller medullary canal volume
2. Decreased cortical thickness and a larger medullary canal volume
3. Equivalent cortical thickness and medullary canal volume
4. Increased cortical thickness and larger medullary canal volume
5. Decreased cortical thickness and a smaller medullary canal volume

 

Corrent answer: 1

 

As the human body ages the cortical thickness/area decreases and subsequently the diameter/volume of the medullary canal increases. Therefore, a young healthy 25- year-old woman should have thicker cortices and a smaller medullary canal volume than her counterpart at 85 years. A decreased cortical bone area is linked to increased fracture risk.

 

Stein et al studied femurs from subjects aged 21-92 years of age. They found that a reduction in cortical area was seen in older specimens and this change was more

pronounced in female specimens.

 

Wrong Answers:

Answer 2: Decreased cortical thickness and a larger medullary canal volume describes the bone characteristics of an elderly patient.

Answer 3: Bone mass decreases with aging and is not constant.

Answer 4. The volume of bone remains constant with aging, so you can not have both an increased cortical thickness and larger medullary canal volume. Answer 5: The volume of bone remains constant with aging, so you can not have a decrease in both cortical thickness and medullary canal volume.

 

223. Which of the following is NOT a described complication of corticosteroid injections?

 

1. Local flare in surrounding tissues
2. Apoptosis of myocytes
3. Skin pigmentation changes
4. Fat atrophy
5. Facial flushing

 

Corrent answer: 2

 

Corticosteroids have not been shown to cause apoptosis of myocytes when injected extra-articularly. Each of the other answers have been described.

 

Cole and Schumacher provide a review of current uses of corticosteroid injections, and emphasize that how accurately the injection is placed affects the outcome.

 

Kumar and Newman report prospectively on 672 patients who received 1147 intra- and extra-articular injections. Their overall complication rate was low (16%) with injection site pain (mild) and bleeding constituting the majority of cases. There were 4 instances of fat atrophy in the extra-articular group, and

4. cases of syncope or dizziness in the intra-articular group. They did not discuss the efficacy of their injections.

 

224. A surgeon chooses a periarticular locking plate with unicortical proximal locking screws for an extra-articular distal femur fracture as seen in Figure A. Compared to an identical construct with bicortical unlocked proximal screw fixation, the periarticular locking plate with unicortical locking screws has which biomechanical properties?

 

1. Greater torsional and axial fixation strength
2. Less torsional but greater axial fixation strength
3. Equal torsional and axial fixation strength
4. Greater torsional but less axial fixation strength
5. Less torsional and axial fixation strength

Corrent answer: 2

 

Unicortical locking plates have characteristically less torsional strength than bicortical locking plates and bicortical non-locking plates. Axial strength is improved with locking plate fixation.

 

Zlowodzki et al studied the LISS periarticular locking plate with unicortical proximal fixation in a distal femur model and found superior axial fixation strength (134%) but worse torsional strength (68%) compared to a fixed angle blade plate with non- locking bicortical screw fixation.

 

Locked plating was reviewed by Haidukewych and Ricci which highlighted the added cost, unique complications, and they recommended the use of locked plating only in situations when unlocked constructs have demonstrated poor outcomes.

 

225. In rat models looking at the effect of malnutrition on fracture healing, amino acid supplementation in a nutritionally deprived rat increases all of the following EXCEPT

1. Serum albumin
2. Body mass
3. Quadriceps total protein content
4. Fracture callus mineralization
5. Insulin-like growth factor 1 (IGF-1) mRNA expression

 

Corrent answer: 5

 

The study by Hughes et al found that essential amino acid supplementation (glutamine, arginine, and taurine) following femoral fracture in a protein- malnourished rat model increases serum albumin, body mass, quadriceps total protein content, and fracture callus mineralization. Expression of IGF-1 and

IGF-2, myosin, actin, and VEGF mRNA were all significantly decreased in the amino acid supplemented group compared to the malnourished group. The malnourished group is thought to have upregulation of mRNA expression in attempt to increase the amount of protein product that is translated, however the lack of amino acid building blocks in the malnutrition group was a barrier to appropriate protein synthesis.

 

The study by Day et al created a malnourished rat femur fracture model by administering a 6% protein diet. They found that administering a 20% protein diet in the post-fracture period yielded a greater cross-sectional area of the

fracture callus and callus stiffness compared to the 6% protein malnourished group.

 

226. The statistical power of a study is best defined by?

 

1. 1 - probability of type-II (beta) error
2. True positive/(true positive + false negative)
3. True negative/(false positive + true negative)
4. 1 - probability of type-I (alpha) error
5. [True positive/(true positive + false negative)] / false-positive rate

 

Corrent answer: 1

 

The power of a study is an estimate of the probability of finding a significant association in a research study when one truly exists. The power is defined by

1 - probability of type-II (beta) error, and is often set at 80%. For example, a power of 80% means that if the intervention works, the study has an 80% chance of detecting this and a 20% chance of randomly missing it. A type-II or beta error occurs when one falsely concludes that there is no significant association when there actually is an association (resulting in a false-negative study that rejects a true alternative hypothesis). The type-II or beta error can be determined if Type I error rate and sample size are known. A type-I or alpha error occurs when a significant association is found when there is no true association (resulting in a false-positive study that rejects a true null hypothesis). The alpha level refers to the probability of a type-I (alpha) error and is usually set for most studies at 0.05. Answer 2 is the formula for sensitivity. Answer 3 is the formula for specificity. Answer 5 is the formula for the positive likelihood ratio. The references by

Kocher and Wojtys are excellent reviews of basic biostatistic principles.

 

227. A 55-year-old female with a history of metastatic breast cancer develops shoulder pain without any trauma. Which of the following is involved with the findings shown in Figures A and B?

 

1. IL-4
2. RANK
3. TNF-alpha
4. OPG
5. Sox-9

 

Corrent answer: 2

 

Osteoclastic bone resorption is the final common mechanism for osteolysis, whether due to a pathologic lytic lesion, macrophage activation in particle wear, or normal remodeling. The RANK-RANKL mechanism controls the coupling of osteoblast and osteoclast activation. Figures A and B show an osteolytic lesion in the humerus in a patient with known metastatic breast carcinoma.

 

RANKL is expressed from osteoblasts and bone-marrow stromal cells. When RANKL binds to the RANK receptor (receptor/activator of NF-[kappa]B) on the cell membrane of osteoclasts it stimulates differentiation from osteoclast progenitor cells to mature osteoclasts. Mature osteoclasts proceed with osteoclastic bone resporption.

Osteoprotegerin (OPG) acts as a decoy receptor by binding to RANKL and blocking the interaction between RANKL and the RANK-receptor and consequently inhibiting osteoclast formation and

activation.

 

Illustration A depicts the RANK/RANKL involvement in tumor metastatic spread.

 

228. Laboratory values of a normal serum calcium and parathyroid hormone can be found in which of the following disease states?

1. Primary hyperparathyroidism
2. Type I vitamin D deficient rickets
3. Type II vitamin D deficient rickets
4. X-linked hypophosphatemic rickets
5. Nutritional rickets

 

Corrent answer: 4

 

Hypophosphatemic rickets is caused by the inability of kidney proximal tubules to reabsorb phosphate due to a mutated PHEX gene, found on the X chromosome. PHEX is thought to protect extracellular matrix glycoproteins from proteolysis. Hypophosphatemic rickets shares many clinical similarities with nutritional rickets but shows PTH levels that are not elevated, even with calcium and phosphate abnormalities.

 

Pettifor reviews the advances in molecular genetics in the understanding and possible treatments in tumour-induced osteomalacia/rickets.

 

The review article by Carpenter discusses the X-linked disorder including its clinical manifestations, the wide spectrum of disease severity, and complications of the disease in adult patients.

 

Illustration A is a table that details the laboratory values associated with each type of rickets.

 

229. An 80 year-old female undergoes ORIF of her hip fracture without any complications. A hospitalist consult was obtained for medical clearance pre- operatively, and she was diagnosed with osteoporosis. Which of the following treatment scenarios will lead to the best management of the patient's osteoporosis?

 

1. Schedule a follow-up appointment with the patients primary care physician to initiate therapy
2. Order a physical therapy consult and initiate an exercise plan
3. Have the patient meet with a nutritionist to increase her calcium and vitamin D intake
4. Start bisphosphonates, and have the patient follow-up with her primary care physician
5. Perform a metabolic work-up as an inpatient, and set-up an appointment in an osteoporosis clinic

 

Corrent answer: 5

 

The initiation of appropriate osteoporosis treatment following hip fractures occurs at a surprisingly low rate. Physical therapy and dietary changes are not appropriate initial treatments for osteoporosis, and bisphosphonate therapy should be prescribed by the physician who will be following and managing the patient's osteoporosis.

 

Miki et al performed a prospective randomized trial where they compared the rates of osteoporosis treatment initiation. The percentage of patients who were on pharmacologic treatment at 6 months post-injury was 58% in the group whose treatment was directed by the orthopedic surgeon and osteoporosis clinic, and 29% when managed by the primary care physician alone.

 

230. The elements chromium, molybdenum, and cobalt are basic components of which of the following implant materials?

 

1. Aluminum oxide
2. Cobalt alloy
3. Stainless steel
4. PMMA
5. Tantalum

 

Corrent answer: 2

Cobalt alloys are extremely strong and are well-suited to applications requiring longevity. Strength of the implant is improved by the addition of molybdenum. Corrosion resistance is addressed by the addition of chromium, which also increases the hardness of the implant.

 

Incorrect Answers:

Answer 1: Aluminum oxide (Al2-03) is a ceramic used in bearing surface applications.

Answer 3: Stainless steel is an iron-carbon alloy, which also has silicon, manganese, molybdenum, and chromium in lesser amounts. It is much more susceptible to both galvanic and crevice corrosion than cobalt alloys.

Answer 4: PMMA is a cement made of poly-methyl-methacrylate.

Answer 5: Tantalum is very resistant to corrosion, and is often used in implants where bony ingrowth is desired.

 

231. Which of the following scenarios of treatment of a humerus fracture best achieves low strain at the fracture site and high stiffness of the treatment construct?

 

1. Functional bracing of a transverse midshaft fracture
2. Comminuted midshaft fracture with locked bridge plating
3. Short oblique fracture with interfragmentary lag screw and locked neutralization plate
4. Uniplane external fixation of a spiral open fracture
5. Oblique fracture with intramedullary nail fixation

 

Corrent answer: 3

 

Strain in fractures is calculated by dividing the interfragmentary movement by the size of the fracture gap. Strain must be very low (2%) for primary bone healing to occur, and should be less than 10% for secondary bone healing to occur. Stiffness refers the ability of the construct to resist movement under applied loads. Answer 3 describes a situation where primary bone healing is

the goal. For this to occur, there must be no significant gapping at the fracture site, there must be low strain between fracture fragments, and the construct must be stiff.

 

None of the other answers would accomplish this. Functional bracing and intramedullary fixation both accomplish healing through formation of fracture callus, or secondary healing. A comminuted fracture treated with locked bridge plating relies on less stiffness to allow for secondary healing between fragments. However, since there are many fracture fragments, the strain is distributed among them and therefore remains low. A uniplane external fixator is very unlikely to accomplish low strain and high stiffness in this setting.

232. A 67-year-old man complains of low-grade fevers and calf pain 2 weeks following a total knee arthroplasty. What is the next appropriate step in management of this patient?

 

1. Plethysmography of lower extremity
2. MRI of lower extremity
3. CT angiography of lower extremity
4. Venous ultrasonography
5. Knee aspiration to evaluate for septic joint

 

Corrent answer: 4

 

Venous ultrasonography is the next best step in this patient's management, due to the clinical picture of a deep venous thrombosis. The most sensitive and specific recommended diagnostic procedure is a venous ultrasonography.

 

In their multi-center study, Haut et al. hypothesized that admission to trauma centers that use duplex ultrasound more frequently would independently predict increased DVT reporting for individual patients. They indeed found that trauma centers ultrasound practice was an independent predictor of DVT diagnosis for individual patients, controlling for patient-level risk factors, but concluded the elevated DVT rates at these centers were due to surveillance bias. As such, they recommend that surveillance for DVT should not be considered as a quality control measure in the care of trauma patients.

 

233. A patient undergoes closed reduction of a bimalleolar ankle fracture dislocation by the ER physician and is sent to your clinic for evaluation. You evaluate the patient and schedule him for surgery. According to the 2009 guidelines, which of the following scenarios would meet criteria for coding the encounter as a new patient?

 

1. You injected his knee in the office almost 3 years ago for osteoarthritis, and have not seen him since
2. He had an arthroscopic operation by your partner 4 years ago
3. You were consulted 1 year ago for shoulder pain when he was hospitalized for chronic renal failure
4. He was seen by your partner in clinic for a herniated disk 2 years ago, but had no procedures performed
5. You performed a hip replacement on him 12 years ago, and his last follow- up was 18 months ago at which time he was doing well

 

Corrent answer: 2

 

Only answer two is correct. The 2009 guidlines clarify that the patient can be defined as new only if he has not been seen by anyone in the physician's same group practice and of the same specialty in the past 3 years. Hand and sports medicine specialists with a CAQ, however, are an exception and are allowed to bill for patients already seen by other orthopedists in the same group as new

patients. This scenario would not qualify as a consultation, since the orthopedic surgeon

is taking over care of the patient's problem and is not merely offering advice to another physician who is already caring for the patient. Consultations do not have the same 3 year time qualification. However, Medicare and many other insurers no longer recognize consultation codes.

 

234. All the following medications binds reversibly to the enzyme COX-1 EXCEPT

 

1. Meloxicam
2. Diclofenac
3. Indomethacin
4. Naproxen sodium
5. Aspirin

 

Corrent answer: 5

 

Aspirin binds irreversibly to the cyclooxygenase enzyme. Aspirin acetylates platelet cyclooxygenase and permanently inhibits thromboxane (TX) A2 production leading to its antiplatelet effects. The other NSAID's listed above bind reversibly with COX-1.

 

Patrono et al discuss the pharmokinetics and platelet effect of both low dose and regular dose aspirin. Nonsteroidal anti-inflammatory drugs compete dose- dependently with arachidonate for binding to platelet cyclooxygenase.

 

235. In the treatment of patients with rheumatoid arthritis, TNF-alpha is blocked by which of the following agents?

 

1. Tocilizumab
2. Anakinra
3. Etanercept
4. Abatacept
5. Rituximab

 

Corrent answer: 3

 

Etanercept is a biochemically designed soluble p75 tumor necrosis factor receptor immunoglobulin G fusion protein, which blocks the downstream

effects of TNF.

 

Methotrexate is a chemotherapy agent used to inhibit lymphocytes. Gold inhibits monocytes, while sulfasalazine is an anti-inflammatory decreasing the production of

prostaglandins and leukotrienes. Rituximab inhibits B-cells as it

is a monoclonal antibody to CD20 antigen. Anakinra (Kineret) is a recombinant IL-1 receptor antagonist. Abatacept (Orencia) is a selective costimulation modulator that binds to CD-80 and CD-86 (inhibits T cells). Tocilizumab (Actemra)is an IL-6 receptor inhibitor (2nd line treatment for poor response to TNF-antagonist therapy).

 

Pisetsky wrote an editorial in NEJM discussing the development of TNF blockers through research, and the potential for the use of Etanercept in patients with juvenile RA through its inhibition of lymphotoxin-alpha.

 

236. Which of the following medications when combined with methotrexate has been shown to be more effective than methotrexate alone in the treatment of rheumatoid arthritis?

 

1. Nitrofurantoin
2. Rifampin
3. Azithromycin
4. Erythromycin
5. Doxycycline

 

Corrent answer: 5

 

Tetracycline was initially used in the treatment of rheumatoid arthritis (RA) because Mycoplasma was thought to be the causative agent. It was later found that tetracyclines have biologic effects on the inflammatory and immunologic cascade by inhibiting collagenase activity. Collagenase is an enzyme involved

in breaking down macromolecules in the connective tissue, contributing to the pathologic changes of RA.

 

In a prospective study, O'Dell et al found that initial therapy with methotrexate plus doxycycline was superior to treatment with methotrexate alone. Furthermore, similar results for low-dose and high-dose doxycycline suggested that antimetalloproteinase effects were more important than the antibacterial effects.

 

237. When using C-arm fluorocopy, patient radiation exposure will be increased with which of the following?

 

1. The extremity is positioned closer to the image intensifier
2. A larger body part is imaged compared to a smaller body part
3. Use of radiation beam collimation
4. Mini C-arm fluroscopy is used instead of large C-arm fluroscopy
5. Decreased duration of imaging

 

Corrent answer: 2

Patient radiation exposure will be increased if a larger body part is imaged compared to a smaller body part.

 

The first study by Giordano et al used radiation dosimeters for large and mini c-arm machines. They found that elevated exposure levels can be expected when larger body parts are imaged, when the extremity is positioned closer to the x-ray source, and when the large c-arm is used over the mini c-arm.

 

The second study by Giordano et al also used dosimeters for a mini c-arm and found that the surgical team is exposed to minimal radiation during routine

use of mini-c-arm fluoroscopy, except when they are in the direct path of the radiation beam. They list factors to decrease radiation exposure to patient and surgeon including: minimizing exposure time, reducing exposure factors, manipulating the x-ray beam with collimation, orienting the fluoroscopic beam in an inverted position relative to the patient, strategic positioning of the surgeon within the operative field, judicious use of protective shielding during imaging, and maximizing the distance of the surgeon from the radiation beam.

 

Illustration A shows that arrangement #1 has the body part half-way between the radiation source and image intensifier. Arrangement #2 has the the image intensifier acting as an arm table for the body part with the radiation source further away. Arrangement #1 has more radiation exposure than #2. The distance between the x-ray tube and the body part is doubled in arrangement

#2 compared to arrangement #1. This increased distance correlates to a reduction in exposure according to the inverse square law (reduction in radiation intensity with greater distance from the x-ray source).

 

238. You are seeing a 13-year-old girl for asymptomatic flat feet and recommend observation. In educating this patient/family about general bone health, you recommend what amount of daily dietary calcium for your patient?

1. 250mg - 500mg 2. 500mg - 750mg 3. 750mg - 1000mg

4. 1000mg - 1500mg

5. over 1500mg per day

 

Corrent answer: 4

 

A 13-year-old would require a daily dietary calciuim intake of 1000 to 1500mg/d.

 

According to the National Osteoporosis foundation daily calcium requirements for children are as follows: Age 1-3yrs - 500mg/d, Age 4-8yrs - 800mg/d, Age

9-18yrs - 1000 to 1500mg/d.

 

The level 5 review by Tortolani et al. states that adults aged >50 yrs require 1200 to 1500 mg/d of calcium and lactating women require more daily calcium (2000mg per day).

 

239. Rifampin is highly effective against phagocytized intracellular Staphylococcus aureus especially in combination with other antibiotics because of its:

 

1. Hydrophilic activity
2. High cell penetration
3. Structural similarity to penicillin
4. Structural similarity to vancomycin
5. Beta-lactamase activity

 

Corrent answer: 2

 

Based on the choices above, rifampin works well synergistically with other antibiotics because of its high cell penetration.

 

Rifampin is a bactericidal antibiotic that blocks the function of RNA polymerase and subsequent RNA transcription. It is used to treat both staphylococcus and mycobacterium infections. Because of the high rate of cellular penetration, it is effective against intracellular phagocytized staphylococcus.

 

Darouiche et al. investigated the cellular penetration of seven antibiotics in cultured human umbilical vein endothelial cells. Lipophilic drugs such as minocycline, ciprofloxacin and rifampin had better cell penetration. Although rifampin was found to have limited killing activity, it potentiated the bactericidal activity of other antibiotics when used in combination.

Illustration A shows a schematic detailing the mechanism of rifampin’s bactericidal action.

 

Incorrect Answers

Answer 1, 3, 4, 5: Rifampin is lipophilic, rendering its ability to cross the cell wall/membrane and exert its actions against RNA polymerase.

 

240. Which of the following medications is a recombinant form of parathyroid hormone that has been found to stimulate new bone formation in patients with postmenopausal osteoporosis?

 

1. Risedronate (Actonel)
2. Zoledronic acid (Reclast)
3. Teriparatide (Forteo)
4. Ibandronate (Boniva)
5. Alendronate (Fosamax)

Corrent answer: 3

Teriparatide (Forteo) comprises the first 34 amino acids of the 84 amino acid parathyroid hormone(PTH) and can reproduce the primary effects of PTH by activating adenyl cyclase. The review article by Barnes et al describes PTH as the primary regulator of calcium and phosphate metabolism in bone and kidney. Intermittent PTH treatment increases bone mineral density by increasing coupled remodeling between osteoclast- mediated bone resorption and osteoblast-mediated new bone formation. Continuous dosing would stimulate bone resorption. Thus, an intermittent dosing in the form of daily injections of teriparatide have a net effect of stimulating new bone formation. The Level 1 study by Neer et al found that daily treatment with parathyroid hormone (1-34) reduced the risk of nonvertebral fractures by 35 percent at the 20-µg dose and by 40 percent at the 40-µg dose and reduced the risk of nonvertebral fragility fractures by 53 and 54 percent, respectively. Risedronate(Actonel), alendronate(Fosamax), ibandronate(Boniva), and zoledronic acid (Reclast) are nitrogen containing bisphosphonates that inhibit osteoclast resorption by inhibiting the enzyme farnesyl diphosphate synthase.

 

241. All of the following are advantages of a body-controlled prosthesis compared to a myoelectric prosthesis for patients with upper extremity

amputations EXCEPT:

 

1. Better for heavy labor activities
2. Decreased amount of harnessing
3. Decreased amount of therapy for training
4. Lighter weight
5. Less prosthetic maintenance

 

Corrent answer: 2

Body-controlled prosthesis typically require more harnessing (harness ring best placed at C7 past the midline toward the non-amputated side) compared to myoelectric prostheses. Body-powered prostheses are better for heavy labor activities and are triggered by shoulder flexion and abduction. Myoelectric prostheses are cosmetically appealing, adapt well for sedentary use, and can be used for overhead manuevers.

 

The article by Carey et al is a case study of a bilateral upper extremity amputee patient. They found that elbow range of motion was better with the body-controlled prosthesis, but required more shoulder flexion for continous grasping tasks.

 

The article by Scott is a commentary on the role of proprioceptive feedback in upper extremity prosthesis design. The Level 4 article by Silcox et al reviews

44 upper extremity amputees and found 50% rejected the myoelectric prosthesis completely. Of those who had both types, 32% rejected the conventional prosthesis.

 

242. A 10-year-old male presents to the emergency department after his left ankle came into contact with the rotating blades of a lawn mower. He has a deep open laceration over his medial malleolus, and a radiograph is shown in Figure A. There is concern for a peripheral

growth plate injury in the region of the groove of Ranvier. What is this region of the growth plate responsible for?

 

1. Longitudinal bone growth
2. Appositional bone growth
3. Supplying cartilage cells to the articular surface
4. Calcification of the matrix within the growth plate
5. Organization of the growth plate into distinct zones of proliferation and hypertrophy.

 

Corrent answer: 2

 

The groove of Ranvier is a wedge-shaped zone of cells contiguous with the epiphysis at the periphery. It supplies chondrocytes to the periphery and is responsible for appositional growth of the physis. The perichondrial ring, which is another component of the physis periphery, is a dense fibrous ring which is critical to the overall stability of the growth plate. Figure A represents a rare Salter-Harris VI injury which most commonly result from traumatic lacerations or burns and cause injury to the growth plate periphery. The proliferative zone of the growth plate is responsible for longitudinal growth, and the resting zone coordinates growth plate organization and supplies developing cartilage cells.

Calcification of the matrix within the growth plate occurs in the hypertrophic zone.

 

243. A trial is peformed evaluating the use of ultrasound to diagnose meniscus tears in 100 athletes with knee pain. Figure A displays the data from the ultrasound examinations compared to the gold standard of arthroscopic diagnosis. The statistician calculates the following equation: 86/[86+4]= 95.5%. What statistical term does this

equation best describe?

 

1. Sensitivity
2. Positive predictive value
3. Specificity
4. Negative predictive value
5. Likelihood ratio

 

Corrent answer: 3

 

Specificity is the probability that a test result will be negative in patients without disease. The specificity is determined by measuring the true negatives (n=86 in this case) divided by the sum of the true negatives (n=86) and false positives (n=4); equaling 95.5% in this case. The sensitivity is defined as the portion of true positives over all of those that have the disease. The positive predictive value is the number of patients with a positive test result who actually have the disease (true positives) divided by all positive results (true and false positives). The negative predictive value is the opposite of this.

These are both dependent on disease prevalence. Likelihood ratio equals the sensitivity divided by [1-specificity].

 

The referenced articles by Wojtys et al and Kuhn et al are reviews of the basic statistical tools useful for conducting and interpreting scientific experiments.

Illustration A is a diagram that demonstrates the relationship between predictive values, specificity, and sensitivity.

 

244. Effective communication between physicians and patients has been shown to affect all of the following EXCEPT?

 

1. Patient satisfaction
2. Patient adherence to treatment
3. Physician satisfaction
4. Incidence of malpractice suits
5. Incidence of Stark II litigation

 

Corrent answer: 5

 

Communication affects patient satisfaction, adherence to treatment, physician satisfaction, and is the most common factor in the initiation of malpractice suits. It does not affect the incidence of Stark II litigation.

 

Section 1877 of the Social Security Act, often referred to as the "Stark law," prevents physicians from making referrals to entities in which the physician has a financial relationship. Stark II presently provides for civil money penalties not to exceed

$100,000 for each "arrangement or scheme" that a person knows or should know has a principal purpose to violate the statute.

 

Tongue et al, surveyed patients and colleagues and found that orthopaedic surgeons are ranked poorly for their communication skills, and are perceived as lacking empathy for their patients. They emphasized that communication

affects patient satisfaction, adherence to treatment, and physician satisfaction, and have also been cited as the most common factor in the initiation of malpractice suits.

Beckman et al, in a Level IV study, reviewed 45 plaintiffs' depositions selected randomly from 67 malpractice suit depositions over a 2-year period. They

found that plaintiffs perceived a problematic relationship with their physician in (71%), deserting the patient (32%), devaluing patient and/or family views (29%), delivering information poorly (26%), and failing to understand the patient and/or family perspective (13%).

 

Roter et al, analyzed telephone communication patterns between 537 physician-patient encounters. They found that the communication patterns that delivered the highest

satisfaction among patients and physicians actually occurred the least often (16%).

 

245. Which of the following statements is FALSE regarding juvenile idiopathic arthritis(JIA)?

 

1. To meet diagnostic criteria, persistent arthritis must occur in any joint for greater than 6 weeks before the age of 16 years
2. Radiographic evaluation may be unremarkable
3. Cervical involvement may lead to atlantoaxial instability
4. A patient with suspected JIA should undergo slit lamp examination by an ophthalmologist
5. Definitive diagnosis of JIA is confirmed by serologic evaluation

 

Corrent answer: 5

 

All of the listed options are true statements EXCEPT for Option 5. Definitive diagnosis of JIA is NOT confirmed by serologic evaluation.

 

JIA (formerly juvenile rheumatoid arthritis) characterizes the onset of chronic arthritis in childhood. The diagnosis is made on pattern recognition with a thorough history and physical exam to exclude other etiologies including septic arthritis, malignancy, rheumatic fever, inflammatory bowel disease, and systemic lupus erythematosus. Serologic testing may be useful to rule out other etiologies of disease. However, rheumatoid factor (RF), anti-nuclear antibody (ANA), and HLA-B27 are neither sensitive nor specific enough to be useful for screening or confirmation testing.

 

Borchers et al. reviews the classification schemes of JIA. They report many of these classifications rely on subjective symptoms and do not have serologic tests useful for differentiation.

Tucker reviews the etiology and immunopathology of JIA. New research has been directed and better understanding the genetics and both cellular and humoral immune response prevalent in juvenile arthritis.

 

Punaro et al. reviews the clinical evaluation and diagnosis of JIA. The diagnosis relies heavily on history and physical exam. Serologic tests are useful in excluding other possible causes of pain (such as septic arthritis) but are less useful in confirming or differentiating the different subtypes of juvenile

arthritis.

 

Incorrect Answers:

Answer 1, 2, 3, and 4 are all true statements.

246. Which of the following osteoconductive bone graft substitutes resorbs faster than the rate at which bone growth occurs?

 

1. Coralline hydroxyapatite
2. Collagen-based matrix with hydroxyapatitie coating
3. Calcium phosphate
4. Calcium sulfate
5. Tricalcium phosphate

 

Corrent answer: 4

 

Calcium sulfate has a compressive strength similar to cancellous bone but resorbs quickly.

 

The review article by Hak discusses that calcium sulfate resorbs faster than bone growth occurs and is resorbed in 4-12 weeks. Tricalcium phospate, coralline hydroxyapatite, and collagen-based matrices with hydroxyapatite coating have compressive strengths similar to cancellous bone and can take 6 months to 10 years to fully resorb. Calcium phosphate has a compressive strength 4-10 times greater than cancellous bone and resorption takes approximately 1 year.

 

The article by Frankenburg et al reports the results of 70 dogs undergoing an osteotomy with subsequent allograft or calcium phosphate filling and were then sacrificed at interval times over a 4-month period. The osteotomies filled

with allograft reached approximately 100% of the strength of the control tibiae by four weeks, whereas the tibiae that had been treated with cement reached their maximum load to failure by eight weeks. Tha authors found trends (no statistical signficance) showing stiffness, displacement at maximum load, and

energy to failure was greater with the allograft but conclude that calcium phosphate is well tolerated and may be useful in difficult fractures.

 

247. A 24-year-old female presents with a transverse midshaft humerus fracture. Which of the following implants would create the most compression on both the far and near cortices?

 

1. Compression plate with concave bend (ends bowed towards bone)
2. Large fragment locking plate with 3 bicortical locking screws proximal and distal to the fracture
3. Intramedullary nail
4. Compression plate with convex bend (ends bowed away from the bone)
5. Sarmiento style fracture brace

 

Corrent answer: 1

 

Placing a concave bend in the plate during compressive plating results in compressive forces at both the near and far cortices (Illustration A). As described in the AO manual

of fracture fixation, this technical pearl helps to ensure that osteosynthetic forces occur on both sides of the fracture. This technique is most useful in transverse fractures and can be used in any transverse fracture, not just humeral shaft fractures.

 

248. Which of the following agents has been shown to exert its effect by inhibiting protein prenylation and GTPase formation?

 

1. Selective Cox-2 inhibitors
2. Alendronate
3. Cholecalciferol
4. Etidronate
5. Indomethacin

Corrent answer: 2

 

Bisphosphonates are a class of antiresorptive bone agents. They are currently indicated to treat diseases that involve osteoclast-mediated bone resorption. Nitrogen containing bisphosphonates (alendronate, pamidronate, risedronate) exert their effects by inhibiting protein prenylation and GTPase formation.

Non-nitrogen containing bisphosphonates (etidronate, clodronate, tiludronate) induce osteoclast apoptosis by forming a nonfunctional molecule that competes with adenosine triphosphate (ATP) in the cellular energy

metabolism. Common diseases currently treated with bisphosphonates include osteoporosis, Paget's disease, and metastatic bone disease. Research is underway for use in other conditions, such as AVN.

 

Morris et al review current treatment regimens for the most common treatment indications for this drug class and they note there is no long term data regarding current treatment.

 

Burnei et al discuss the treatment options for osteogenesis imperfecta which include both medical and surgical treatments. Bisphosphonates have been shown to reduce the fracture risk for this disease, but no long term data exists.

249. Which of the following configurations creates the least radiation exposure for the operative surgeon during upper extremity surgery?

 

1. Imaging the thumb positioned against the x-ray source with the standard C- arm
2. Imaging the wrist positioned against the x-ray source with the standard C- arm
3. Imaging the thumb positioned against the image intensifier with the mini C- arm
4. Imaging the wrist positioned against the image intensifier with the mini C- arm
5. Imaging the thumb positioned against the x-ray source with the mini C-arm

 

Corrent answer: 3

 

Radiation exposure with fluoroscopy is reduced by using the mini C-arm, imaging a smaller body part, and moving the body part away from the xray source (near the image intensifier).

 

Giordano et al evaluated radiation exposure to the surgeon and patient with

both the standard fluoroscopy unit and mini C-arm in different configurations for different body parts. Greater radiation exposure was associated with use of the standard fluoro unit, larger body parts, and moving the body part closer to the xray source (away from the image intensifier).

 

Athwal et al used radiation dosimeters to evaluate radiation exposure to the surgical team during cadaver wrist surgery with a standard C-arm and a mini C-arm. Radiation exposure was significantly greater with use of the standard C-arm.

 

Illustration A identifies the x-ray source and image intensifier.

 

250. Which of the following is true regarding rigid locking plate constructs in fracture fixation?

1. Locking plates always enhance fracture healing more than non-locking plating
2. Locking plates reduce interfragmentary strain more than non-locking plating
3. Locking plates are best utilized in diaphyseal fractures
4. Locking plates are contraindicated in patients with osteoporosis
5. Fractures treated with anatomic reduction and locked plate fixation demonstrate more strain than fractures treated with intramedullary fixation

 

Corrent answer: 2

 

Locking plate technology functions through the threaded locking of the screw heads into the plate to create a fixed angle construct. Illustrations A and B show the locking threads of a locking screw and locking plate. This results in

less screw toggle and resistance to screws backing out. Locked plates provide stiffer constructs than conventional plates and intramedullary nails and thus reduce interfragmentary strain.

 

Egol et al reviews the principles of locked plating and the advantages and disadvantages as compared to conventional plating. Locked plates are especially useful in severely comminuted fractures, osteoporotic bone, and fractures of metaphyseal bone.

 

Stoffel et al performed in vivo plating of sheep tibia following osteotomy. Overbending the plate and augmenting with a lag screw resulted in decreased strain at the osteotomy site.

 

Claes et al use a biomechanical model to hypothesize the magnitude of strain necessary at a fracture site to determine the differentiation of callus tissue. Primary bone healing occurs with anatomic fracture reduction and absolute stability as seen with lag screw compression of an oblique fracture. Secondary healing occurs through enchondral ossification when fractures are fixed with relative stability as seen with intramedullary nail constructs.

251. A 30-year-old male with Protein C deficiency sustains a large subarachnoid hemorrhage and bilateral calcaneus fractures after falling off of a roof. The patient has been in the intensive care unit for

5 days for monitoring of his head injury. All of the following factors are appropriate reasons to obtain a helical chest CT scan EXCEPT:

 

1. Elevated alveolar-arterial gradient (> 20 mm Hg or 2.7 kPa) on arterial blood gas
2. Pulse oximetry reading of 99% with respiratory rate of 35 breaths/min
3. Pulse rate of 125 beats/min with new onset right bundle branch block
4. Paco2 > 35 mm Hg (or 4.7 kPa) on arterial blood gas
5. Pao2 < 80 mm Hg (or 10.7 kPa) on arterial blood gas

 

Corrent answer: 4

 

All of the options listed except for Paco2 >35mmHg are indications of a pulmonary embolism. Most patients are hypoxic (Pao2 < 80 mm Hg), hypocapnic (Paco2 < 35 mm Hg), and have a high A-a gradient (> 20 mm Hg).

Pulse oximetry is not a reliable option to arterial blood gas measurements because patients can hyperventilate to maintain adequate oxygenation. Protein C deficiency is an inherited thrombophilia that increases the risk of venous thromboembolism(VTE). This patient is also at risk for VTE secondary to his sedentary status in the ICU and contraindication to administration of chemical VTE prophylaxis because of his subarachnoid hemorrhage.

 

The review article by Della Rocca and Crist notes that conversion of the external fixator to an intramedullary implant may be accomplished safely within 2 weeks without an increased rate of infection. In the event, there would be suspcicion of an intraoperative pulmonary embolism, correct treatment includes adhering to the principles of damage- control orthopaedics and changing operative plans to a provisional (e.g. external fixator) from a definitive treatment (e.g. intramedullary nail) and obtaining a helical chest CT scan promptly.

 

The article by Knudson et al is a prospective study of 113 trauma patients that received either SCD's or low dose heparin for DVT prophylaxis. They found no statistical difference between the 2 groups in preventing thromboembolism. They did find that patients with thromboembolism were older, spent more hospital days immobilized, and received more transfusions. High-resolution (helical or spiral) chest CT angiography has become the first line modality for diagnosing pulmonary embolism and should be performed after the operation.

 

252. Patients with transradial amputations are considered the best candidates for a myoelectric prosthesis. Each of the following are advantages of a myoelectric device compared to a body controlled device EXCEPT:

 

1. Provide more proximal function
2. Better cosmesis
3. More sensory feedback
4. Can be used in any position including overhead activities
5. Require less gross limb movement

 

Corrent answer: 3

 

Myoelectric devices provide less sensory feedback than body controlled devices. Other disadvantages of myoelectric prosthesis include that they are heavier, more expensive, and require more maintenance. Myoelectric prostheses work by using surface electrodes that detect electrical activity from the muscles of the residual limb and transmitting these impulses to the electric motor. Patients with transradial amputations are considered the best candidates for a myoelectric prosthesis because only the terminal device needs to be activated at this level of amputation.

 

The article by Carey et al is a case study of a bilateral upper extremity amputee. They found that elbow range of motion was better with the body- controlled prosthesis, but required more shoulder flexion for continous grasping tasks.

 

The article by Uellendahl is a review of upper extremity myoelectric prosthesis technology.

 

253. The chi-square test is considered the most appropriate statistical test to analyze categorical data, but is unreliable if there are less than

5 events in any of the groups or the sum of all cells is less than 50. Which test is preferred in place of the chi-square test when these small sample sizes are encountered?

 

1. Fisher exact test
2. Regression analysis
3. Two-sample t-test
4. Mann-Whitney test
5. Analysis of variance (ANOVA)

Corrent answer: 1

In the situation where there are relatively few total cases (the sum of all cells is less than approximately 50 or less than 5 events in a cell), the Fisher exact test is the most appropriate substitute for the chi-square test.

 

Fisher's exact test is a statistical significance test used in the analysis of contingency tables. Although in practice it is employed when sample sizes are

small, it is valid for all sample sizes. It is one of a class of exact tests, so called because the significance of the deviation from a null hypothesis (e.g., P-value) can be calculated exactly, rather than relying on an approximation that becomes exact in the limit as the sample size grows to infinity, as with many statistical tests.

 

The chi-square test is a simple method of comparing two proportions, such as a difference in nonunion rates(%) between two groups of fracture patients. The two-sample t-test is a parametric test that compares two means and the Mann-Whitney test is a non- parametric test that compares two means. Analysis of variance (ANOVA) compares one dependent variable among three or more groups. Regression analysis is used to

estimate the association between a response variable and a series of known explanatory variables (includes simple, multiple, and logistic regression).

 

The article by Kuhn et al reviews the basics of statistical inference.

 

254. All of the following are characteristic of synovium affected by rheumatoid arthritis (RA) EXCEPT:

 

1. Prominent intimal hyperplasia
2. Decreased apoptosis
3. Increased angiogenesis
4. Disruption of the basement membrane
5. Abundant lymphocytes

 

Corrent answer: 4

 

The basement membrane is not disrupted in rheumatoid arthritis-affected synovial tissue, as synovium lacks a true basement membrane.

 

Normal synovium consists of two layers, the intimal and the sublining, and two types of cells, type A and B. In RA, the following changes to the synovium are seen: 1) hyperplasia, with the intimal lining increasing from two cell layers to

10-20 layers 2) decreased apoptosis of the lining 3) increased angiogenesis and 4) abundant lymphocytes around vessels, forming lymphoid follicles.

 

The synovial pannus is invasive granulation tissue that contains fibroblast-like synoviocytes, but few inflammatory cells. The synovial cells in the pannus have anchorage-independent growth and invasive capabilities, allowing them to directly attack and destroy articular cartilage.

Koch et al. note that the possible contributions of angiogenesis to the proliferation of the inflammatory synovial pannus and the ingress of inflammatory leukocytes into the synovial tissue in RA have been extensively studied. Relevant angiogenesis inducers seen in RA include FGF-2, VEGF, TGFß, TNFa, IL-1, IL-8, VCAM-1, among others.

Modulation of angiogenesis may be a viable therapeutic option for RA in the future.

 

Incorrect Answers:

Answer 1, 2, 3, 5: Synovium affected by rheumatoid arthritis has all of these characteristics.

 

255. Which of the following drugs is an IL-1 antagonist typically used as a second

line agent in the treatment of rheumatoid arthritis?

 

1. Anakinra
2. Methotrexate
3. Leflunomide
4. Adalimumab
5. Etanercept

 

Corrent answer: 1

 

IL-1 receptor antagonist (IL-1Ra) is a naturally occurring molecule that blocks the biologic effects of the pro-inflammatory cytokine IL-1. A recombinant form of human IL-1Ra, anakinra, is used to manage rheumatoid arthritis patients who are refractory to more conventional forms of treatment. Methotrexate and leflunomide are DMARD's, and are typically prescribed if low dose corticosteroids are ineffective. Adalimumab and etanercept are both TNF-alpha blockers.

 

Kalliolias et al summarize clinical trials and meeting abstracts regarding the experience with anakinra in the treatment of patients with rheumatic diseases. They conlcude that anakinra is less effective than TNF-alpha blockers in the treatment of RA, and can be successful in treating adult-onset Still's disease and systemic-onset juvenile idiopathic arthritis (previously known as juvenile rheumatoid arthritis, or JRA).

 

256. Congenital unilateral transverse absence of the forearm results from vascular insult to which of the following?

 

1. Notochord
2. Endoderm
3. Limb bud mesoderm
4. Apical ectodermal ridge
5. Epithelial ectoderm

 

Corrent answer: 4

 

The apical ectodermal ridge lies directly over the fetal limb bud and directs longitudinal growth of the limb. Illustration A depicts proper limb development following the apical ectodermal ridge. Illustration B demonstrates transverse absence (also known as congenital amputation) following an insult to the

apical ectodermal ridge. A vascular injury to the limb bud mesoderm or epithelial ectoderm may result in congenital deformity, but not a complete

transverse absence of the limb.

 

257. A locked plate used in a bridge plate fashion is biomechanically most similar to which of the following fixation methods?

1. Lag screw
2. Lag screw plus non-locked neutralization plate
3. External fixator without compression
4. Lag screw plus locked neutralization plate
5. External fixator used in compression mode

 

Corrent answer: 3

 

The definition of a bridge plate is one where (1) there is no direct compression between the bone ends at the fracture site and (2) the screws are placed far from the fracture site (thus increasing the working length of the construct). Keeping the screws remote from the fracture site prevents disturbance of the blood supply and allows more motion of the construct. This is ideal for spanning comminuted segments, not for simple fracture patterns. A bridge plate with locking screws functions the same as an external fixator, except

that it is placed internally. Like plates, external fixators can be designed to compress across a fracture or osteotomy site.

258. Which of the following bone modulators primarily utilizes adenylyl cyclase as a mediator for its cellular signaling within osteocytes?

 

1. SMADs
2. Parathyroid hormone (PTH)
3. Insulin-like growth factor II (IGF-II)
4. Bone morphogenetic protein 2 (BMP-2)
5. Transforming growth factor-Beta (TGF-ß)

Corrent answer: 2

Parathyroid hormone receptor activation primarily stimulates the pathway involving adenylyl cyclase/G-alpha stimulatory protein/cAMP/protein kinase A in osteocytes. BMPs target undifferentiated mesenchymal cells and signal through serine/threonine kinase receptors. Intracellular molecules called SMADs act as signaling mediators for BMPs.

IGF-II stimulates type I collagen, cartilage matrix production, and bone formation. IGF-II signals through tyrosine kinase receptors primarily. Transforming growth factor-Beta (TGF-ß) stimulates osteoblasts to synthesize collagen and primarily signal through serine/threonine kinase receptors.

 

The review article by Barnes is a review of the use of intermittent PTH administration as a treatment for osteoporosis and its possible role in stimulating fracture healing.

 

Illustration A is an outline of parathyroid receptor signaling with the its predominant pathway on the left and secondary pathway on the right.

 

259. Which of the following administered substances leads to net bone resorption?

1. Zoledronic acid (Reclast) injection once per year
2. Teriparatide (Forteo) injection once daily
3. Alendronate (Fosamax) oral once weekly
4. Teriparatide (Forteo) continuous infusion for 2 weeks
5. Alendronate (Fosamax) oral once daily

 

Corrent answer: 4

 

Teriparatide (Forteo) comprises the first 34 amino acids of the 84 amino acid sequence that make-up parathyroid hormone(PTH) and can reproduce the primary effects of PTH by activating adenyl cyclase. Continuous infusions of Teriparatide result in a persistent elevation of the serum parathyroid hormone concentration, and lead to greater bone resorption than do daily injections. Daily Teriparatide injections cause only transient increases in the serum parathyroid hormone concentration and creates a net anabolic effect on bone. Alendronate is an oral bisphosphonate that decreases bone resorption and can be administered by taking oral dosages of 70mg once weekly or 10mg once daily. Zoledronic acid is also a bisphosphonate that is administered as an annual infusion.

 

The Level 1 study by Neer et al found that daily treatment with parathyroid hormone (1-

34) reduced the risk of nonvertebral fractures by 35 percent at the 20-µg dose and by 40 percent at the 40-µg dose and reduced the risk of nonvertebral fragility fractures by 53 and 54 percent, respectively

 

260. Which of the following defines the working distance of a plate in a plate/screw fracture fixation construct?

 

1. The length of the interfragmentary lag screw
2. The length between the 2 screws closest to the fracture on each end of the fracture
3. The distance from the bone to the plate
4. The length from the screw closest to the fracture to the screw furthest from the fracture on the same end of the plate
5. The length between the 2 screws furthest from the fracture on each end of the plate

 

Corrent answer: 2

 

The working distance is defined as the distance between the 2 screws closest to the fracture. Decreasing the working distance increases the stiffness of the plate fixation construct. An example of the working distance is provided in Illustrations A and B from Hak's review article. Changing the screw position from A to B results in a less rigid construct that is more suitable for secondary bone healing.

 

Stoffel et al review the biomechanics of locking bridge plate constructs. The working distance is the most important determinant of axial stiffness and torsional rigidity.

Decreasing the distance from the plate to the bone, using a longer plate, and increasing the number of screws used also increased stiffness.

Egol et al reviews and compares the biomechanics of locked plates and conventional nonlocked plates. Locked plates are most indicated for diaphyseal- metaphyseal junction fractures in osteoporotic bone, severely comminuted fractures, indirect fracture reduction, and fractures where anatomical constraints prevent plating on the tension side of the bone. Conventional nonlocked plates are the fixation of choice for periarticular

fractures that require anatomic reduction, and nonunions that require compression to enhance healing.

 

261. A 47-year-old man complains of long standing pain involving the right index, middle, and ring fingers. A clinical image is shown in Figure A. A radiograph is provided in Figure B. Which of the following is the most likely diagnosis?

 

1. Gout
2. Osteoarthritis
3. Rheumatoid arthritis
4. Septic arthritis
5. Psoriatic arthritis

 

Corrent answer: 5

 

The clinical presentation and radiograph are consistent with psoriatic arthritis. Figure A shows a swollen "sausage digit" (dactylitis) and nail pitting (onychodystrophy)characteristic of this condition. Figure B demonstrates the classic "pencil-in-cup" radiographic deformity seen in DIP arthritis, a common orthopaedic manifestation of psoriatic arthritis. Psoriatic arthritis affects 5 to

10% of patients with psoriasis of the skin. However, the spectrum of

symptoms varies greatly from mild and self-limiting to destructive arthritis. It most commonly affects the hands and feet, but can also involve the spine and sacroiliac joints. Primary treatment is medicinal with NSAIDS, methotrexate, and TNF-alpha inhibitors.

High infection rates have been reported with surgical intervention. Illustration A is an closer image depicting psoriatic onychodystrophyis. Illustration B illustrates a "pencil-in- cup" deformity.

 

262. Which of the following study designs represent a level III evidence study?

 

1. Prospective, randomized controlled trial
2. Retrospective case-control study
3. Retrospective case series
4. Prospective cohort study
5. Expert opinion

 

Corrent answer: 2

 

The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research. Therapeutic study hierarchy of evidence has been established to better analyze studies in a reproducible fashion. Level I studies include well- designed randomized controlled prospective studies (RCT). Level II include

lower quality designed prospective RCT as well as prospective cohort studies. Level III include retrospective cohort studies and case-control studies. Level IV include case series. Level V include case reports, expert opinion, and personal observation. This is summarized in illustration A. The referenced article by Brighton et al is a review of how the level of evidence has evolved and how the different levels can carry varied amounts of impact on clinical treatments and future research.

263. A prosthetic polycentric knee with hydraulic swing control is chosen for a very active 63-year-old transfemoral amputee. All of the following appropriately describe the features of this prosthesis EXCEPT:

 

1. Flexes in a controlled manner
2. Variable cadence
3. Ability to walk at a moderately fast pace
4. Knee center of rotation is fixed anterior to the line of weight bearing
5. Weighs more than a constant friction knee that has a manual extension locking mechanism

 

Corrent answer: 4

 

A polycentric knee has a variable, not fixed, center of rotation. When the center of rotation is posterior to the line of weight bearing it allows control in the stance phase, but makes flexion more difficult. However, when the center of rotation is anterior to the line of weight bearing, flexion is improved but control is sacrificed. An example of this prosthesis is shown in illustration A.

 

The piston mechanism in the hydraulic knee allows variable cadence by changing resistance to knee flexion. This prosthesis also flexes in a controlled manner by limiting excessive flexion and by extending earlier in the gait cycle.

The polycentric knee with hydraulic swing control is best for active patients who prefer greater utility and variability but it does weigh more than the constant-friction knee hinge that has a manual extension locking mechanism.

 

The review articles by Michael and Friel review the prescription options for lower extremity prostheses.

 

264. Level 1 evidence has shown vitamin C reduces the incidence of reflex sympathetic dystrophy (RSD) or complex regional pain syndrome type I (CRPS) in patients with which of the following?

 

1. Tarsal tunnel syndrome
2. Distal radius fractures
3. Carpal tunnel syndrome
4. Cervical radiculopathy from herniated nucleus pulposis
5. Ankle fractures Corrent answer: 2

Two different prospective, double-blind studies performed by the same institution have shown that vitamin C administration is associated with a lower risk of RSD (i.e CRPS) after wrist fractures. Vitamin C is thought to reduce

lipid peroxidation, scavenge free hydroxyl radicals, protect the capillary endothelium, and inhibit vascular permeability.

The first trial by Zollinger was published in Lancet and included 115 adults with 119 fractures treated with conservative management. They found that RSD/CRPS occurred in four (7%) wrists in the vitamin C group (500mg daily for 50 days) and 14 (22%) in the placebo group.

 

The second trial by Zollinger published in JBJS included 317 adult patients sustaining 328 distal radius fractures treated conservatively. They had allocated treatment groups to 200mg, 500mg, or 1500mg vitamin C dosages

for 50 days. RSD/CRPS occurrence was 4.2% in the 200mg group, 1.8% in the 500mg group, and 1.7% in the 1500mg group and thus the 500mg dosage for

50 days was recommended at the conclusion of the study. Patients making early cast- related complaints to their provider had a higher incidence of developing RSD/CRPS.

 

It should also be noted that a recent double blinded randomized controlled trial by Ekrol et al found no statistical significant benefit of Vitamin C on the outcome of distal radius fractures.

 

265. Which of the following best describes the mechanism by which osteoprotegerin (OPG) plays a role in RANKL-mediated osteoclast bone resorption?

 

1. inhibits RANKL-mediated osteoclast bone resorption by directly binding to RANKL
2. inhibits RANKL-mediated osteoclast bone resorption by directly binding to the RANK receptor on osteoclasts
3. stimulates RANKL-mediated osteoclast bone resorption by directly binding to RANKL
4. stimulates RANKL-mediated osteoclast bone resorption by directly binding to the

RANK receptor on osteoclasts

5. stimulates RANKL-mediated osteoclast bone resorption by directly binding to PTH

 

Corrent answer: 1

 

Osteoclastic bone resorption is the final common mechanism for osteolysis, whether due to a pathologic lytic lesion, macrophage activation in particle wear, or normal remodeling. The RANKL mechanism controls the coupling of osteoblast and osteoclast activation.

RANKL is expressed from osteoblasts and bone-marrow stromal cells. When RANKL binds to the RANKL receptor (receptor/activator of NF-[kappa]B) on the cell membrane of osteoclasts) it

stimulates differentiation from osteoclast progenitor cells to mature osteoclasts. Mature osteoclasts proceed with osteoclastic bone resporption. Osteoprotegerin (OPG) acts as a decoy receptor by binding to RANKL and blocking the interaction between RANKL and the RANK-receptor and consequently inhibiting osteoclast formation and activation.

 

The reference by Clohisy et al reviews recent developments in our understanding of the cellular and molecular events regulating osteoclast- mediated bone resorption and discusses the role of the RANKL pathway in several disease states, including osteolysis associated with inflammatory arthritis and cancer-induced bone loss.

 

The reference by Goater et al studied the potential of OPG gene therapy by evaluating the ability of transfected synoviocytes expressing OPG to prevent wear debris-induced osteoclastogenesis. They found a decrease in the amount of bone resorption in mice with the transfected OPG gene. The RANKL pathway is shown in Illustration A below and further described in the linked video.

 

266. Level 1 evidence has shown Low-intensity Pulsed Ultrasound Stimulation (LIPUS) decreased the time to fracture union in all of the the following injuries EXCEPT?

 

1. Radius shaft fracture
2. Distal radius fracture
3. Tibia shaft fracture treated with casting
4. Tibia shaft fracture treated with reamed intramedullary nailing
5. Scaphoid fracture

 

Corrent answer: 4

Tibia shaft fractures treated with reamed intramedullary nailing do not have Level 1 evidence supporting adjunctive LIPUS treatment. Low-intensity pulsed ultrasound (LIPUS) "bone stimulators" deliver 30mW/cm2 pulsed-waves via an external device over the fracture site.

 

The meta-analysis by Busse et al found 6 randomized, controlled trials evaluating LIPUS. They concluded that low-intensity pulsed ultrasound treatment may significantly reduce the time to fracture healing for fractures treated nonoperatively.

 

The metanalysis cites that Emami et al found no benefit to LIPUS treatment on intramedullary fixed tibial fractures. Injuries described in the metaanalysis as having positive benefits from LIPUS include radius shaft(Cook et al), distal radius(Kristiansen et al), scaphoid(Mayr et al), and tibia treated with casting (Heckman et al).

 

The Level 1 study by Heckman et al of 67 patients found a significant decrease in the time to clinical healing in tibia fractures treated with casting and no serious complications with its use.

 

267. A 58-year-old Jehovah's Witness male presents with severe right hip pain due to osteoarthritis. He has failed exhaustive physical therapy, steroid injections, and activity modifications, and now wishes to proceed with a right total hip arthroplasty. During the procedure, there is profound blood loss with associated hypotension. Which of the following is generally the most preferred method for treating the patient's acute intraoperative anemia?

 

1. Iron supplementation
2. Subcutaneous erythropoietin administration
3. ABO-matched allogeneic blood transfusion
4. Continuous tranexamic acid infusion
5. Use of cell salvage

 

Corrent answer: 5

 

The patient has experienced a greater than expected blood loss during the procedure and has developed hemodynamic instability as a result. Given that the patient is a Jehovah's Witness, the use of a cell salvage (Cell Saver) is most preferred method for treating the patient's acute blood loss anemia.

Signficant intraoperative blood loss is a risk associated with major orthopedic procedures such as joint arthroplasty, and spine, tumor, and trauma surgeries. The most effective method of mitigating this risk is by maintaining good hemostasis during the procedure.

Tranexamic acid (TXA), cell saver, and allogeneic blood transfusion are adjunctive modalities to limit and address excessive intraoperative blood loss. Patients who are Jehovah's Witnesses are generally not amenable to allogeneic blood transfusions but can often be transfused with their own blood. The use of intraoperative cell saver allows for the recycling of the patient's own blood that is obtained with suction, and this can then be used later to transfuse the patient. However, this should be discussed with the patient pre- operatively, as some Jehovah's witnesses may be amenable to allogenic blood transfusion or conversely be opposed to cell saver.

 

Moonen et al. reviewed perioperative blood management in elective orthopedic surgery procedures. The authors stated that the gold standard for preventing intraoperative blood loss was by maintaining adequate hemostasis and dissecting through anatomically correct tissue planes. They proposed the use

of pre-operative erythropoietin and iron supplementation, pre-operative autologous blood donation, platelet-rich plasmapheresis, hypotensive epidural anesthesia, and intra- operative cell saving as adjunctive blood loss management modalities. The authors concluded that allogenic blood transfusion should be based on physiologic variables, risks of disease transmission, and patient preference.

 

Imai et al. performed a retrospective study of intraoperative and postoperative blood loss in patients undergoing primary total hip arthroplasty that were treated with either a control or TXA at various time points in the perioperative period. They found that patients who received TXA either 10 minutes prior to surgery or 6 hours after the original dose had a significant decrease in periopreative blood loss. Postoperative blood loss was significantly decreased

in all patients that received TXA. The authors concluded that TXA is an effective adjunct for minimizing blood loss during arthroplasty procedures.

 

Incorrect Answers:

Answer 1: Iron supplementation would be ineffective in this setting as it takes months for iron to have a meaningful effect on a patient's hemoglobin levels. Postoperative oral iron supplementation has been questionably effective due to the inflammatory effects of the surgical healing process and the implications of iron metabolism similar to anemia of chronic disease.

Answer 2: Preoperative erythropoietin therapy has been used to increase baseline hemoglobin levels in patients that are already anemic. However, in the acute setting, it is unlikely to be effective.

Answer 3: Allogeneic blood transfusion is an unacceptable choice given that Jehovah's Witnesses are known for being averse to receiving allogeneic blood transfusions. This choice would go against this patient's beliefs and autonomy. Answer 4: Tranexamic acid has been shown in several studies to reduce intraoperative and postoperative blood loss during arthroplasty procedures. However, this patient has already experienced profound blood loss with resulting hemodynamic instability, which would make this option ineffective for addressing the patient's blood replacement needs.

 

268. According to the 2008 National Osteoporosis Foundation Guidelines for Pharmacologic Treatment of Osteoporosis, when are bisphosphonates indicated for the treatment or prevention of osteoporosis?

 

1. DEXA T-score between -1.0 and -2.5
2. FRAX calculated 10-year hip fracture risk of >3%
3. FRAX calculated 10-year risk of major osteoporosis-related fracture of

>10%

4. Answers 1 and 2
5. Answers 1 and 3

 

Corrent answer: 4

 

The 2008 National Osteoporosis Foundation Guidelines for Pharmacologic Treatment of Osteoporosis suggests that pharmacologic treatment should be considered for a DEXA T-score between -1.0 and -2.5 at the femoral neck/spine AND 10-year risk of hip fracture ≥ 3%.

 

Osteoporosis affects more than 12 million Americans per year, with the burden falling heaviest on postmenopausal women. Because of decreased bone strength, patients with osteoporosis are susceptible to fragility fractures. With no additional risk factors, a 65- year-old Caucasian woman has an estimated

10% 10-year risk of a fragility fracture. FRAX (World Health Organization Fracture Risk Assessment Tool) calculates 10-year risk of fracture based on the following variables: age, sex, race, height, weight, BMI, history of fragility

fracture, parental history of hip fracture, use of oral glucocorticoids, secondary osteoporosis and alcohol use to calculate 10-year risk of fracture.

 

Unnanuntana et al. discussed the utility of the FRAX tool as an assessment modality for prediction of fracture risk. The authors advocated for treatment with osteopenia (T-score of

-1.0 to -2.5) combined with either a ten-year risk of hip fracture >= 3% or a ten-year risk of major osteoporosis-related fracture

of >= 20% as calculated by FRAX. They also discussed biochemical markers of bone formation and resorption, which are useful for monitoring the efficacy of antiresorptive therapy and may help identify patients at high risk for fracture.

 

Cosman et al. review the 2008 National Osteoporosis Foundation guidelines and support that pharmacologic treatment for osteoporosis should be considered if patients are postmenopausal women or men > 50 years of age AND meet one of the following criteria: have a prior hip or vertebral fracture, a T score -2.5 or less at the femoral neck or spine, OR a T score between -1.0 and -2.5 at the femoral neck or spine AND a 10-year risk of hip fracture

greater than 3% or 10-year risk of major osteoporosis-related fracture greater than 20%. They conclude that DEXA scans should be repeated every 1-2 years if patients are undergoing pharmacologic treatment.

 

Gass et al. review the epidemiology and tiered management strategy for osteoporosis. They discuss the first line prevention, treatment of secondary causes of osteoporosis, and finally pharmacologic interventions, all in an effort to mitigate fracture risk and the burden that osteoporotic fractures on the health care system.

 

Illustrations:

Illustration A outlines the variables taken into account in the FRAX score calculator.

Incorrect answers:

Answer 1: A DEXA T-score less than -2.5 in isolation is an indication for bisphosphonate therapy. However, in the setting of osteopenia (T-score of -1.0 to -2.5), bisphosphonate therapy is indicated only if the patient

ADDITIONALLY has either a ten-year risk of hip fracture >= 3% or a ten-year risk of major osteoporosis-related fracture of >= 20% (or both) as calculated by the FRAX tool.

Answer 2: A 10-year hip fracture risk of >3% as calculated by the FRAX tool in isolation is NOT an indication to begin bisphosphonate therapy. The patient must have documented osteopenia (T-score of -1.0 to -2.5) as well.

Answer 3: A 10-year risk of major osteoporosis-related fracture should be

>20% as calculated by the FRAX tool in order to meet the criterion set forth in the 2008 National Osteoporosis Foundation guidelines. Combined with documented osteopenia (T- score of -1.0 to -2.5), bisphosphonate therapy would be indicated.

Answer 5: A 10-year risk of major osteoporosis-related fracture should be

>20% as calculated by the FRAX tool in order to meet the criterion set forth in the 2008 National Osteoporosis Foundation guidelines.

 

269. Which of the following bone graft substitutes has the fastest resorption characteristics?

 

1. Calcium sulfate
2. Tricalcium phosphate
3. Hydroxyapatite
4. Fibular allograft
5. Cortical iliac crest autograft

 

Corrent answer: 1

 

Of the three bone graft substitutes listed (calcium sulfate, tricalcium phosphate, and hydroxyapatite), calcium sulfate has the fastest resorption characteristics. Fibular allograft and cortical iliac crest autograft are not considered bone graft substitutes.

 

Calcium sulfate, tricalcium phosphate, and hydroxyapatite are all "osteoconductive" bone graft substitutes, meaning that these implants provide a surface and structure that facilitates the attachment, migration, proliferation, differentiation and survival of osteogenic stem and progenitor cells. Each has different chemical, macro- and microstructural properties. Calcium sulfate (plaster of Paris) is a low-molecular weight soluble compound that must be implanted adjacent to viable periosteum to work. It is reabsorbed by a

process of dissolution over a period of 5-7 weeks.

 

Jamali, et al., found that calcium sulphate was completely reabsorbed by 6 weeks. Tricalcium phosphate has compressive strength similar to cancellous bone, but is brittle and weak under tension and shear. It undergoes reabsorbtion via dissolution and fragmentation over 6-18 months; unfortunately less bone volume is produced than tricalcium phosphate absorbed. For this reason, it is used clinically as an adjunct with other less

absorbable substitutes.

 

Moore et al discuss that hydroxyapatite forms the principle mineral content of bone. Synthetically, it is available in ceramic and non-ceramic forms as porous or solid, blocks or granules. HA has good compressive strength, but is weak in tension and shear and brittle making it fracture-prone in shock loading. Ceramic HA preparations are resistant to absorption in vivo, which occurs at 1-

2% per year. Non-ceramic HA is more readily absorbed.

 

270. Which of the following techniques increases strength and stability to an external fixation construct?

 

1. Unicortical pin fixation
2. Decreasing total pin separation distance
3. Increased working distance from the pin to fracture site
4. Decreasing the distance between the bone and the construct
5. Using smaller diameter pins

 

Corrent answer: 4

 

There are several methods that can be used to increase the strength of an external fixation construct. Decreasing the distance from the bar to the bone increases stability and strengthens the construct. Some other methods to increase stability include: good bone- to-bone fracture end apposition, using an increased number of pins, using larger pins, small distance from the near pins to the fracture site (smaller working distance), increased spacing between the near and far pins, and bicortical pin fixation.

 

Tencer et al looked at biomechanical aspects of external fixation systems. They demonstrated that system rigidity could be increased by maximizing pin separation distance in the fracture component and the number of pins used while minimizing pin separation distance across the fracture site and the sidebar offset distance from bone.

 

Incorrect Answers: Answer choices 1,2,3, and 5 all act to decrease external fixation construct strength.

271. A 62-year-old woman with Paget’s disease is started on a non- nitrogen containing bisphosphonate for treatment of her condition.

What is the mechanism of action of this drug?

 

1. Inhibition of farnesyl diphosphate synthase
2. Conversion of drug into a non-functioning ATP-analogue
3. Interference of isoprenylation of small GTPases
4. Inhibition of geranylgeranyl diphosphate synthase (GGPPS)
5. Downregulation of the undecaprenyl diphosphate synthase (UPPS) pathway

 

Corrent answer: 2

 

Bisphosphonates are a class of antiresorptive agents used to treat diseases characterized by osteoclast-mediated bone resorption. Non-nitrogen containing bisphosphonates (such as etidronate) are metabolized into non-functioning

ATP analogues which cause eventual osteoclast apoptosis. Nitrogen containing bisphsphonates (alendrolate/Fosamax and Zoledronic acid/Zometa) act by inhibiting farnesyl diphosphate synthase (FPPS), resulting in decreased prenylation of small GTPases.

 

Reszka et al reviewed nitrogen containing bisphosphonates. They outlined the mechanism of action on farnesyl diphosphate synthase in the cholesterol biosynthesis pathway.

 

Guo et al also reviewed the mechanism of nitrogen-containing bisphosphonates. In addition to showing the decrease in prenylation of GTPase, they were shown to inhibit geranylgeranyl diphosphate synthase (GGPPS), as well as undecaprenyl diphosphate synthase (UPPS).

 

Morris et al reviewed the bisphosphonates currently approved by the FDA. They outlined their use in the treatment of Paget disease, metastatic bone disease and widening applications in OI and fibrous dysplasia.

 

Incorrect answers:

1,3,4,5: Mechanism of nitrogen-containing bisphosphonates.

 

272. A 58-year-old female falls and sustains the injury shown in Figures A and B. Following surgical treatment of the fracture, which of the following is the most appropriate additional investigation?

 

1. MRI of the pelvis
2. Urine electrophoresis
3. CT scan of the pelvis
4. Bone scan
5. DEXA scan

 

Corrent answer: 5

Figures A and B depicts a femoral neck fracture. Medical management of postmenopausal women with fragility fractures (distal radius, femoral neck, vertebral compression fractures) includes dual-energy x-ray absorptiometry (DEXA) testing.

Following the diagnosis of osteoporosis, bisphosphonates, calcitonin or other medical treatments may be initiated.

Oyen et al examined 1794 patients with fractures of the distal radius. As one- third of the men and half of the women had bone mineral density (BMD) suggesting osteoporosis, they concluded that all patients aged 50 or above should have bone densitometry testing.

 

Freedman et al reviewed 1162 women with distal radius fractures. They determined that the rate of diagnostic workup and medical treatment decreases as patient age increases at the time of fracture.

 

273. A 52-year old woman who is not on any hormone replacement therapy (HRT) falls from standing height and sustains the injury seen in Figure A. Review of her medical history reveals that she carries a diagnosis of osteoporosis, and that her latest T-score was -3.0. How much calcium should she have been consuming on a daily basis prior to sustaining her injury?

 

1. 200-400mg

2. 600-800mg

3. 800-1000mg

4. 1000-1500mg

5. >1500mg

 

Corrent answer: 4

The clinical presentation and radiographs are consistent with a distal radius fragility fracture. Based on her medical history of osteoporosis, which is confirmed by a T-score

<-2.5, she should be taking 1000-1500mg of calcium per day at baseline.

 

Tortolani et al reviewed the effects of decreased bone mineral density (BMD) in children. Conditions such as osteogenesis imperfecta (OI), rickets, JRA and neuromuscular disorders are common causes. They outlined the process of skeletal development and the pathophysiology of osteopenia.

 

In a consensus statement, the NIH provided outlines for daily calcium intake for broken down into age groups. In addition, they reviewed the cofactors in calcium metabolism, risks of high calcium levels, health strategies for increasing intake and recommendations for future research in calcium intake.

 

Oyen et al examined 1794 patients with fractures of the distal radius. As one-

third of the men and half of the women had bone mineral density (BMD) suggesting osteoporosis, they concluded that all patients aged 50 or above should have bone desitometry testing.

 

Freedman et al reviewed 1162 women with distal radius fractures. They determined that the rate of diagnostic workup and medial treatment decreases as patient age increases at the time of fracture.

 

274. Longterm bisphosphonate usage has been shown to cause an increased risk of stress reaction leading to fracture at which of the following areas?

 

1. Jaw
2. Lumbar spine
3. Femoral neck
4. Subtrochanteric femur
5. Anterior cortex of tibia

 

Corrent answer: 4

 

Subtrochanteric stress reaction and fracture is a known complication of longterm bisphosphonate use. Imaging typically shows lateral cortical thickening in the subtrochanteric femur (Illustration A). Without discontinuation of bisphosphonate use and prophylactic fixation, this stress reaction can go on to a transverse fracture (Illustration B.)

 

Koh et al studied the complication of femoral cortical stress lesions in patients on longterm bisphosphonate treatment. In their findings, they note that these fractures

occured in the subtrochanteric region, and were preceded by "a dreaded black line," and lateral femoral cortical thickening. All patients with these fractures also reported lateral thigh pain for over one month.

 

Capeci et al did a retrospective review on alendronate therapy and its association with unilateral low-energy subtrochanteric femur and diaphyseal femur fractures. Although a rare complication, they recommended consideration of discontinuing alendronate with the consultation of an endocrinologist if it occurs. They also recommend routine contralateral leg imaging after to rule out contralateral stress fracture. If contralateral stress fracture is found, it should be treated with prophylactic intramedullary fixation.

 

275. The pattern of ambulation shown with the assistive device in Video A is most appropriately described as which of the following?

 

1. Swing-to gait
2. Drag-to-gait
3. Swing-through gait
4. 3-point gait
5. 4-point gait

 

Corrent answer: 1

 

Figure A demonstrates a swing-to gait pattern of ambulation with an assistive device.

Swing-to gait patterns are usually indicated for persons with bilateral lower extremity weakness and requires good upper extremity strength and good overall balance.

 

The review article by Faruqui et al states that a three-point gait pattern is utilized when one of the lower extremities has a non–weight-bearing status. This occurs when the patient moves both crutches and the injured limb forward bearing his weight on the crutches and then follows with all of his weight on the uninjured limb. The swing-through gait pattern is the fastest mode of crutch ambulation but requires more energy expenditure. An antalgic

gait is a nonspecific term that describes any gait abnormality resulting from pain.

 

Illustration A is a video that demonstrates a 4-point gait. Illustration B is a video showing a swing-through gait. Illustration C is a video that that demonstrates a drag- to gait.

 

276. The sensitivity of a serologic assay is defined as which of the following?

 

1. True positives / (true positives + true negatives)
2. False negatives / (false negatives + true positives)
3. False positives / (false positives + false negatives)
4. (True positives + false positives) / (true negatives + false negatives)
5. True positives / (true positives + false negatives) Corrent answer: 5

The sensitivity of a test is the probability that test results will be positive in patients with disease. Specificity is the proportion of individuals who are truly free of disease who are so identified by the test. Positive predictive value is the proportion of patients with a positive test who have the disease. Negative predictive value is the proportion of patients with a negative test who do not have the disease. For a screening or diagnostic test, its accuracy is its overall ability to identify patients with disease (true positives) and without disease (true negatives).

 

Illustration A is a video tutorial on statistic definitions commonly tested on the OITE.

 

277. Which of the following is true regarding the COX-2 enzyme?

 

1. It regulates normal cellular processes and is the primarily constitutive form of the COX enzymes
2. It decreases prostaglandin production in bone in the presence of certain osteotropic factors
3. It is thought to be necessary for normal endochondral ossification during fracture healing
4. Inhibition of COX-2 has been definitively shown to impede bone healing in human clinical studies
5. Pharmocologic COX-2 inhibition commonly leads to more gastric irritation than COX- 1 inhibition

 

Corrent answer: 3

 

Basic science and animal studies have shown that the COX-2 enzyme plays a role in endochondral ossification in certain fracture healing models.

 

Zhang et al utilized wild-type, COX-1 knockout (KO), and COX-2 KO mice to demonstrate that COX-2 plays an essential role in both endochondral and intramembranous bone formation during skeletal repair. They found that the healing of stabilized tibia fractures in mice was significantly delayed in COX-2

KO models. Furthermore, the histology of the COX-2 KO models was characterized by a marked reduction in osteoblastogenesis that resulted in a high incidence of fibrous nonunion.

 

Austin et al in their Instructional Course Lecture review NSAID therapy in orthopedics, and they provide the following information regarding COX-2. The COX-2 enzyme is expressed at low levels unless it is induced by cytokines and inflammatory mediators and is responsible for the upregulation of the inflammatory system. Normally, COX-2 function to break down arachidonic acid into prostaglandins, thereby increasing their concentration at the site of injury under the influence of osteotropic factors such as TNF-alpha.

Pharmocologic inhibition of COX-1 has been associated with significant gastric irritation, as the COX-1 enzyme is constitutively expressed and is partly responsible for maintaining the homeostatic gastric environment. Finally, no human clinical studies to date have definitively shown that COX-2 inhibitors delay bone healing.

 

278. Which of the following is true of both calcium phosphate and calcium sulfate?

 

1. They have high resistance to shear forces
2. They have high resistance to torsional forces
3. They are contraindicated in spinal fusion
4. They provide a scaffold for bone progenitor cells
5. They are not biocompatible with stainless steel orthopedic implants

 

Corrent answer: 4

Calcium phosphate and sulfate materials are biocompatible materials that are widely used in orthopedic surgery. They have low tensile and shear stress properties. They serve as osteoconductive void-fillers that prevent the in- growth of soft tissue and provide a suitable environment for bone healing.

 

Khan et al reviewed the key features of optimal bone graft substitutes. They concluded that one of three essential elements are needed: (1) osteoinductive factors, (2) osteoconductive capabilities and (3) osteogenic stem cells.

Legros reviewed calcium-based bone substitutes, describing their origins, compositions and physical forms. He highlighted their ability to promote cellular function and reviewed the three-dimensional geometry which allows them to bond to BMPs and become osteoinductive agents.

 

Bucholz reviewed synthetic bone grafts in depth. Synthetic porous substitutes have numerous advantages over autografts and allografts including their unlimited supply, easy sterilization, and storage. The relative advantages and disadvantages of ceramic implants as well as the indications and clinical experience of several of the synthetic bone grafts is reviewed.

 

Incorrect answers:

Answer 1: Both have low resistance to shear forces. Answer 2: Both have low resistance to torsional forces. Answer 3: Both are used in spinal fusion.

Answer 5: Both are used with stainless steel and titanium implants as they are highly biocompatible.

 

279. Calcitonin plays a role in bone metabolism by which of the following mechanisms?

 

1. Decreasing osteoclast activity by directly binding to receptor on the osteoclast
2. Decreasing osteoclast activity by blocking the receptor activator for nuclear factor ligand (RANKL) pathway
3. Increasing osteoblast activity by receptor activator for nuclear factor ligand (RANKL) pathway
4. Decreasing osteoclast activity by stimulating PTH to activate adenylyl cyclase
5. Increasing osteoclast activity by directly binding to receptor on the osteoclast

Corrent answer: 1

 

Calcitonin inhibits osteoclastic bone resorption directly by binding to the osteoclast. Calcitonin decreases osteoclast number and activity, as well as decreases serum calcium. Of additional note, osteoclasts account for the bone resorption seen in metastatic bone disease and multiple myeloma.

 

Osteoclasts are derived from the monocyte/macrophage lineage. Differentiation and function of osteoclasts are regulated by RANKL and osteoprotegerin (OPG). RANKL is secreted by osteoblasts (under the influence of factors such as PTH and 1,25- dihydroxyvitamin D) and attaches to the receptor, RANK, on the membrane of monocyte/macrophage to initiate osteoclast differentiation. OPG is a pseudoreceptor that binds RANKL and halts osteoclast differentiation and function.

 

Illustration A shows a schematic representation of osteoclast differentiation and activity. Illustration B is an additional cartoon depicting the interaction of osteoblasts and osteoclasts (E=estrogen, P-C-P=bisphosphonates, CT=calcitonin). Illustration V is a video tutorial of RANK, RANK-L, and OPG and their role in postmenopausal osteoporosis.

 

280. A 35-year-old female complains of 1 month of right hip pain during ambulation. Her medical history includes end-stage renal disease for which she is on hemodialysis three times per week. A radiograph of the right hip, spine, and skull are shown in Figures A-C. Figure D shows a histology microphotograph of a biopsy specimen. All of the following laboratory findings are associated with this condition EXCEPT?

 

1. Hypophosphatemia
2. Hypocalcemia
3. Decreased 1,25-(OH)2-vitamin D3
4. Increased alkaline phosphatase
5. Increased BUN

Corrent answer: 1

The clinical presentation is consistent for a pathologic hip fracture due to renal osteodystrophy, which would be associated with hypocalcemia, decreased

1,25-(OH)2-vitamin D3, increased alkaline phosphatase, and increased BUN. Renal osteodystrophy would not be associated with hypophosphatemia. Phosphate levels would be increased (hyperphosphatemia).

 

Renal osteodystrophy is secondary hyperparathyroidism due to renal retention of phosphate resulting in hyperphosphatemia, decreased serum ionized

calcium levels, and resultant increased PTH release. Hyperparathyroidism increases bone resorption, to normalize serum calcium levels by releasing the osseous storages of calcium. The various sites of bone resorption include the subperiosteal region of the phalanges, the phalangeal tufts, proximal femur, proximal tibia, proximal humerus, distal clavicle, and calvarial trabeculae.

Verlaan et al. found that primary hyperparathyroidism is most often due to unregulated secretion of parathyroid hormone from a parathyroid adenoma.

 

Figure A shows coarsened trabeculae and insufficiency fractures called Looser's zones.

Figure B shows a "rugger jersey" spine appearance while Figure C

shows punctate trabecular bone resorption in a "salt and pepper" appearance that is characteristic of secondary hyperparathyroidism. Figure D shows increased osteoblasts and osteoclasts lining the widened osteoid seams.

 

281. A patient with chronic renal disease would expect which of the following endocrine abnormalities?

 

1. Decreased production of PTH
2. No change in production of PTH
3. Increased production of PTH
4. Increased production of TSH
5. Decreased production of TSH

Corrent answer: 3

A patient with chronic renal disease would have an increased production of parathyroid hormone.

 

Renal osteodystrophy (ROD)is a pathologic bone condition in patients with underlying kidney disease. The most common endocrine abnormality is increased PTH secretion. Vitamin D, calcium and phosphate balance is carefully regulated by the kidneys, liver, parathyroid gland and bone. In patients with kidney disease, calcium is wasted, leading to low serum calcium

concentrations. Serum phosphate is increased. In response to this, the parathyroid glands upregulate their production of PTH to affect bones, the GI tract and the kidney.

 

ROD can be classified as high and low-turnover. High-turnover is marked by an increase in PTH secretion and leads to parathyroid gland hyperplasia and elevated levels of PTH which persists after correction of the kidney disease.

This manifests as bone disease and osteitis cystica. Low-turnover ROD is more common in the setting of dialysis and proper medical management leading to lower levels of PTH with characteristic bone lesions marked by low levels of bone formation.

 

Skeletal manifestations include metaphyseal enlargement, frontal bossing, bowing of long bones and genu varum. The histology is non-specific, as there are abundant multi- nucleated giant cells and abundant osteoclast activity in marrow stroma.

 

Tejwani et al. reviewed the pathophysiology of ROD. They reviewed the orthopedic implications of kidney disease and its effect on bone quality. They provided an overview of medical and surgical treatment of patients with kidney disease.

Illustration A shows the physiology of PTH. Decreased serum calcium leads to the release of PTH which stimulates the kidney, bone, and GI tract to increase serum calcium levels. High serum calcium levels in return act as negative feedback on the parathroid gland, lead to a decrease in PTH and subsequent decrease in the serum calcium levels.

 

Incorrect Answers:

Answer 1,2,3: PTH would be increased.

Answer 4 and 5: The thyroid gland is not involved with ROD, and therefore TSH would not be affected.

 

282. A 27-year-old male undergoes intramedullary nailing of a midshaft tibia fracture with static locking proximally and distally. There is minimal healing noted 3 months postoperatively and the decision is made to dynamize the nail. For intramedullary nail dynamization, an interlocking screw should be placed in which of the holes shown in Figure A?

1. A only
2. C only
3. B only
4. A and C
5. C and B

 

Corrent answer: 1

 

The portion of the long slot hole labeled A is the dynamic interlocking site because it allows the proximal tibia to collapse with weight bearing. Placement of an interlocking screw in holes B or C would lead to static locking of the nail.

 

In general, axially stable fractures can be locked dynamically in the long slot at the time of initial fracture fixation. This is referred to as primary dynamization. Axially unstable fractures should be locked statically both proximally and distally. In the setting of a long bone nonunion where it is felt that further fracture site compression may aid in healing, the nail can undergo secondary dynamization by either removing the proximal interlocking screw, or by moving the proximal interlocking screw from the static to dynamic slot in

the nail.

 

Illustration A shows the static and dynamic slots of the tibial nail.

 

283. Which of the following antibiotic families inhibit bacterial DNA gyrase?

1. Quinolones
2. Penicillins
3. Aminoglycosides
4. Macrolides
5. Sulfonamides

 

Corrent answer: 1

 

Quinolones are a class of antibiotics which act by inhibition of bacterial DNA gyrase. Penicillins interfere with bacterial cell wall synthesis. Aminoglycosides and macrolides interfere with bacterial protein synthesis by acting on the 30S and 50S ribosome subunits respectively. Sulfonamides interfere with bacterial folic acid metabolism.

 

Levine and DiBona review fluoroquinolones as a class of antibiotics and describe their potential beneficial and adverse effects in the treatment and prevention of musculoskeletal infections. While not frequently used in musculoskeletal infection, fluoroquinolones appear to be very effective in the treatment of osteomyelitis and infections involving prosthetic implants like hip and knee replacements.

 

284. A 3-year-old African-American child presents with irritability, fever, and a warm, swollen leg. Imaging shows an area concerning for osteomyelitis and trans- cortical biopsy reveals multiple Salmonella species. This child most likely also has which of the following conditions?

1. Osteogenesis imperfecta
2. Child abuse
3. Thalassemia
4. Sickle cell anemia
5. Renal failure

 

Corrent answer: 4

 

Salmonella osteomyelitis is directly associated with sickle cell anemia. No documented cases of Salmonella osteomyelitis have been seen secondary to renal failure, osteogenesis imperfecta, or child abuse. While one documented case of Thalassemia minor related osteomyelitis has been shown to be caused by Salmonella species, this is the only documented case and as such sickle cell anemia is more likely choice.

While the most likely cause of osteomyelitis in sickle cell anemia is still Staphylococcus aureus, Salmonella osteomyelitis almost exclusively occurs in patients with sickle cell anemia. The exact mechanistic cause of susceptibility to Salmonella osteomyelitis in sickle cell anemia isn't entirely known, however it is thought the spread of Salmonella from the GI tract is facilitated by the intravascular sickling in the bowel. In addition, the impaired immunological function of patients with sickle cell disease prevents appropriate clearance of Salmonella related infections.

 

285. A 78-year-old female presents with increasing foot pain and deformity. A review of her medication list shows that she is currently on infliximab and sulfasalazine. She reports that she had a synovectomy of her MTP joints 7 years ago that was complicated by a MSSA superficial wound infection. Radiographs are shown in Figures

A-C. The surgeon is planning a reconstructive forefoot surgery including first MTP arthrodesis, resection arthroplasties with pinning of the lesser MTP joints, and closed osteoclasis of the interphalangeal joints. Which of the following risk factors would MOST likely contribute to the development of a postoperative surgical site infection(SSI) in the upcoming planned operation.?

 

1. Patient's age
2. Implantation of hardware for MTP arthrodesis
3. Continuing the use of sulfasalazine in the perioperative and postoperative period
4. Continuing the use of infliximab in the perioperative and postoperative period
5. History of prior MSSA superficial wound infection

 

Corrent answer: 5

 

History of previous surgical site infection is the most significant risk factor for the development of a surgical site infection in a patient with rheumatoid arthritis of the foot.

 

Bibbo et al. performed a Level 3 study of rheumatoid patients undergoing elective foot/ankle surgery to evaluate the effects of TNF-alpha inhibition therapy on wound complications and surgical site infections. They compared

16 patients that were taking Anti-TNF-alpha inhibiting medications (etanercept or infliximab) compared to 15 patients that did not receive TNF-alpha

inhibition therapy. At 10-month follow-up they found that total complications (healing +

infection) in the TNF-alpha inhibition therapy patients demonstrated a lower complication rate than the control group.

 

den Broeder et al. performed a retrospective review of rheumatoid patients undergoing elective orthopaedic surgery. They stratified the patients into 3 groups: Group 1 did not use anti-TNF, cohort 2 used anti-TNF but had either stopped (2A) or continued anti- TNF preoperatively (2B). Elbow surgery, foot/ankle surgery, and prior skin or wound infection were associated with increased risk of SSI. They found that perioperative use of anti-TNF medications were not significantly associated with an increase in SSI rates.

 

Illustration A shows an example of a rheumatoid forefoot reconstruction with first MTP arthrodesis, resection arthroplasties and pinning of the lesser MTP joints, and closed osteoclasis of the interphalangeal joints.

 

Incorrect Answers:

Answer 1: While elderly age might increase the risk of infection, it is not at significant as a history of prior surgical site infection.

Answer 2: While surgical implants increase the risk of infection, it is not at significant as a history of prior surgical site infection.

Answer 3 and 4: Studies have not shown that sulfasalazine or infliximab increase the risk of surgical site infection.

 

286. Which of the following complaints is most often reported by patients receiving care from an orthopaedic surgeon?

 

1. Long waits for patient visits
2. Refusal to refill narcotic prescriptions
3. Lack of technical skills by provider
4. Lack of medical knowledge of provider
5. Lack of empathy by provider

 

Corrent answer: 5

Orthopaedic surgeons performing interviews on patients receive the lowest patient satisfaction at failing to offer empathetic responses.

 

The JAMA article by Levinson et al reviewed audio tape conversations of primary care physicians and surgeons interacting with patients. The study did not find any communication behaviors to distinguish between claims vs no- claims surgeons. Both surgeons with greater and less than 2 malpractice

claims had similar length of patient visits, use of humor, use of facilitation, and statements of orientation.

 

287. Which of the following definitions best describes the phenomenon of load relaxation?

1. Constant loading causing material to continue to deform over time
2. Stress at failure (the ultimate stress) divided by the strain at failure (the ultimate strain)
3. Decreased peak loads over time with the same amount of elongation
4. Stress is proportional to strain up to a limit
5. Strain divided by the time that the load is applied

 

Corrent answer: 3

 

Load relaxation is characterized by decreased peak loads over time with the same amount of elongation.

 

Screen performed a study on tenocytes and tendon fascicles. It was found that viscoelasticity and relaxation behavior within isolated tendon fascicles is dominated by fiber sliding mechanisms and proteoglycans have a role in the mechanisms of strain transfer within the tendon.

 

Incorrect Answers:

Answer 1: Creep is defined as the constant loading causing material to continue to deform over time

Answer 2: Young's modulus is defined as the stress divided by the strain. It is important to note that this only applies during the linear portion of the stress/strain curve (during elastic behavior).

Answer 4: Hooke's law states that stress is proportional to strain up to a limit Answer 5: Strain rate is defined as the strain divided by the time that the load is applied

 

288. You are caring for a 50-year-old male who is 2 years status-post a work related pilon fracture. Since this is a workers compensation case, your patient is interested in settling his claim. When can his claim be legally settled?

1. Once the fracture has united
2. 2 years post-injury
3. Following release to light duty work
4. Following release to full duty work
5. Not until maximum medical improvement is declared by you as the treating physician

 

Corrent answer: 5

According to the referenced workers compensation board of New York medical guidelines, a workers compensation claim can only be settled once maximum medical improvement (MMI) is reached, as documented by the treating physician. The maximum medical improvement post injury is functionally based, rather than based on fracture healing, the time post injury, or the patients ability to return to work. The specific rules for workers compensation vary by state.

 

289. Which of the following best describes plastic deformation?

 

1. Change in length of a material under loading that returns to its original length once the load is removed
2. Progressive deformation of a material in response to a constant force over an extended period
3. The ability of a material to resist deformation
4. Change in length of a material under loading that does not return to the original length once the load is removed
5. The relative measure of the deformation of an object due to a load

 

Corrent answer: 4

 

Plastic deformation is defined as an irreversible change in length after removing the load during the plastic range on a stress-strain curve.

 

The stress-strain curve is found in Illustration A. Objects in the elastic zone of the curve will return to their normal shape when the load is removed. This is termed elastic deformation. Objects in the plastic zone will not return to their normal shape when the load is removed. This is termed plastic deformation. The yield point marks the transition between the elastic and plastic zones.

 

Incorrect Answers:

Answer 1: This is the definition of elastic deformation. Answer 2: This is the definition of creep.

Answer 3: This is Young's Modulus. Answer 5: This is the definition of strain.

 

290. When discussing metal implants and devices, which of the following best describes fatigue?

 

1. Load at which a material fractures
2. Progressive deformation due to a constant force over an extended period
3. Change in the stress-strain relationship dependent on the rate of loading
4. Failure at a submaximal tensile strength level after numerous loading cycles
5. Change in mechanical properties as a result of the direction of a load

 

Corrent answer: 4

 

Fatigue is a characteristic of metal defined as failure below the ultimate tensile strength after numerous loading cycles.

 

Bong et al reviewed the biomechanics of lower extremity intramedullary nailing. They detailed the intrinsic (material properties, cross-sectional shape, anterior bow, diameter) properties and extrinsic (reaming, comminution and locking screws) properties on nail biomechanics.

 

Hou et al investigated the effects of design and microstructure of tibial screws on nail biomechanics. They tested the mechanical strength of a both-ends- threaded screw and an unthreaded bolt and compared them to five commercially available screws in 3-point bending. As the main cause of failure was mechanical overloading, they concluded that screw thread removal could increase the fatigue life of interlocking devices.

 

Incorrect answers:

Answer 1: Load at which a material fractures is ultimate strength

Answer 2: Progressive deformation due to a constant force over an extended period is creep

Answer 3: Change in the stress-strain relationship dependent on the rate of loading is viscoelasticity

Answer 5: Change in mechanical properties as a result of the direction of a load

describes an anisotropic property

 

291. A 58-year-old woman falls down while walking her dog and sustains the low- energy injury shown in Figures A and B. Which of the following lab values is most likely to be abnormal in this patient?

 

1. Hydroxylproline
2. 25-hydroxy cholecalciferol (25 OH vitamin D)
3. Parathyroid hormone-related protein (PTHrP)
4. Sry-type high-mobility-group box transcription factor-9 (Sox-9)
5. LRP5 (low-density lipoprotein receptor-related protein) Corrent answer: 2

This patients history and radiographs demonstrate a low energy distal radius fracture, which are common in middle and older age females with underlying osteoporosis. 25- hydroxy cholecalciferol (25 OH vitamin D) would be the most appropriate laboratory test in this patient who sustained a fall from a standing height (low energy). Vitamin D3 is

converted to 25-OH vitamin D in the liver and then becomes the active hormone form, 1,25-OH vitamin D, or the inactive hormone form, 24,25-OH vitamin D, in the kidney. Osteomalacia is a metabolic bone disease where defective mineralization results in a large amount or unmineralized osteoid and is a qualitative defect as opposed to a quanitative defect like osteoporosis/osteopenia.

 

Pieper et al conducted a study looking at the values of 25-OH vitamin D in

1800 patients that recently sustained a hip fracture. They found that 51% of the patients were at or below the clinically meaningful threshold of 15 ng/mL. They concluded that physicians should be encouraged to check and monitor patients' serum levels of 25-OH vitamin D.

 

Binkley et al present a review recommending selective 25-OH vitamin D lab testing in patients. They report that barriers to universal use include the presence of 2 forms of vitamin D- ergocalciferol (D2) and cholecalciferol (D3), as well as the hydrophobic nature of vitamin D.

 

The review by Templeton discusses the many factors that can lead to osteopenia including eating disorders, smoking, alcoholism, endocrinopathies, GI disease, hepatobiliary disease, and corticosteroids. Peak bone mass is attained before 30 years of age, and failure to attain adequate bone mass at this time is one of the main causes in the development of osteoporosis.

 

292. Which of the following statements defines creep, as it relates to material properties?

 

1. Progressive deformation response to constant force over an extended period of time
2. A solid material's ability to deform under tensile stress
3. The ability of a material's mechanical properties to vary according to the direction of load
4. The rupture of a material under repeated cyclic stresses, at a point below the normal static breaking strength
5. The ability of a material to absorb energy and plastically deform without fracturing

 

Corrent answer: 1

 

Creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material. Creep is an undesirable property of orthopaedic bio-materials because they release frictional forces necessary to maintain rigid internal fixation. In total hip arthroplasty polyethylene liners, creep is the plastic deformation of the acetabular liner that occurs due to loading without the production of wear debris or particles.

 

Incorrect Answers:

2. This is the definition of ductility
3. This is the definition of anisotropy. Bone is anisotropic. 4-This is the definition of fatigue failure

5-This is the definition of toughness.

 

293. MecA is the bacterial gene which encodes for a penicillin-binding protein that alters the efficacy of beta-lactam antibiotics. Which of the following species of bacteria are known to produce mecA?

 

1. Clostridium dificile
2. Clostridium tetani
3. Vancomycin-resistant enterococcus
4. Methicillin-resistant staphylococcus aureus
5. Streptococcus epidermidis

 

Corrent answer: 4

 

Methicillin-resistant Staphylococcus aureus is the most common carrier of the mecA gene. This gene may also be found in Staphylococcus aureus and Streptococcus pneumoniae species and provide penicillin resistance for these bacteria. None of the other listed bacteria are known to harbor mecA in their bacterial genome.

 

Marcotte and Trzeciak review community-acquired MRSA with specific focus on diagnosis and treatment. They discuss the differences between community-

acquired and hospital-acquired MRSA. Specifically, they emphasize bacterial gene products like mecA which alter the bacterial susceptibility towards common antibiotics, and provide appropriate treatment options for common MRSA infections.

 

294. A 55-year-old male presents with a 6 month history of low back pain. Radiographs of the spine are shown in Figures A and B and a lateral knee radiograph is shown in Figure C. A urine specimen is exhibited in Figure D. What is the most likely diagnosis in this patient?

 

1. Disseminated idiopathic skeletal hyperostosis (DISH)
2. Ochronosis (alkaptonuria)
3. Chondrodysplasia punctata (Conradi–Hünerman)
4. Homocystinuria
5. Ankylosing spondylitis

 

Corrent answer: 2

 

The patients history, radiographs, and urine studies are consistent with a diagnosis of ochronosis which is a degenerative arthritis caused by alkaptonuria.

 

Cetinus et al. present a case report and review article stating that alkaptonuria is a rare inborn autosomal recessive defect of the homogentisic acid oxidase enzyme system (tyrosine and phenylalanine catabolism). Excess homogentisic acid deposits in joints (leading to chondrocalcinosis as shown in Figure C) and then polymerizes, leading to early arthritis. Ochronotic spondylitis which

usually occurs during the fourth decade of life, includes progressive degenerative changes and disc space narrowing and calcification.

 

Zhao et al. present a case report and review article discussing the orthopaedic manifestations of alkaptonuria. Arthroscopic findings showed large areas of darkly pigmented full-thickness cartilage defects as demonstrated in Video A.

 

Figures A and B demonstrate vertical syndesmophytes (ossification of the

annulus fibrosis of the intervertebral disc) extending from the body of one vertebra to the adjacent vertebra. Syndesmophytes are also seen in ankylosing spondylitis. Figure C shows chondrocalcinosis of the knee. Figure D shows darkened urine caused by polymerization of homogentistic acid Figure Illustration A shows a knee with ochronosis

undergoing total knee arthroplasty.

 

295. Which of the following determines when a patient involved in a Worker's Compensation claim is allowed to choose their treating physician?

 

1. Federal statute
2. Health insurance carrier policy
3. County statute
4. State statute
5. Employer human resources policy

 

Corrent answer: 4

 

The ability of a patient to choose their own physician during a Worker's Compensation claim is determined according to the individual state Workers' Compensation laws.

 

The Level 2 study by Chaise et al followed 233 carpal tunnel decompression patients and reviewed their time off work according to insurance status. They

found that Worker's Compensation(49 days) was second only to being civil servant (56 days) for longest time off work. Independent workers returned to work the quickest (17 days) and returned in approximately 1/3 of the time.

 

The reference by Cook discusses changes in Pennsylvania state legislation regarding Workers Compensation. It emphasize the importance of physicians to be familiar with their state legislation.

 

296. A 32-year-old man has a 10-month history of bilateral toe swelling and foot pain. A clinical photo showing his toes is shown in Figure A. On examination of his feet he has tenderness along the posterior tibial tendon bilaterally which worsens with single-leg heel rise maneuvers. Standing radiographs of the feet are normal without deformity of the lesser toes. A clinical photo of his fingernails are shown in Figure B. Which of the following diagnoses is MOST likely?

1. Pseudogout (chondrocalcinosis)
2. Gout
3. Psoriatic arthritis
4. Rheumatoid arthritis
5. Scleroderma (systemic sclerosis)

Corrent answer: 3

The history, examination, and images are consistent with a diagnosis of psoriatic arthritis. Psoriatic arthritis is associated with entheses and often presents in the foot with plantar fasciitis, achilles tendinitis, and posterior tibial tendonitis. Dactylitis (Figure A) and nail pitting (Figure B) are common in psoriatic arthritis.

 

Psoriatic arthritis is a seronegative spondyloarthropathy that affects approximately 20% of patients with psoriasis. HLA-B27 is positive in approximately 50% of patients. Typical psoriatic skin plaques (scaly extensor surface, silvery plaques) usually precede the

arthritis, but in 20% of patients, the arthritis occurs first. When medical management with DMARDs is exhausted, operative treatment with osteotomy, arthroplasty, or fusion may be warranted.

 

Illustration A shows a common radiographic finding of a “pencil-in-cup” deformity of the foot from periarticular bony erosions.

 

297. Which of the following genetic defects does not follow Mendelian patterns of inheritance?

 

1. Defect in the fibroblast growth factor (FGF) receptor 3
2. Mutation of a gene coding for a sulfate transport protein
3. Defect in the Gs-alpha protein
4. Defect in the fibrillin gene
5. Deficient activity of the enzyme ß-glucosidase (glucocerebrosidase) Corrent answer: 3

Defect in the Gs-alpha protein, leading to McCune-Albright syndrome, do not follow Mendelian patterns of inheritance.

 

Gs mutations are seen in fibrous dysplasia including monostotic (80%), polyostotic (20%) or, rarely as part of a syndrome (McCune Albright). Fibrous dysplasia is not inheritable and exhibits mosaicism, whereby the random mutation in the GNAS gene occurs early in development and as a result there is a portion of normal version of the GNAS gene, while other cells have the mutated version. McCune-Albright syndrome (polyostotic fibrous dysplasia, café-au-lait spots, precocious puberty) is caused by a sporadic mutation of the Gs-alpha subunit of the receptor/adenylyl cyclase–coupling G proteins and does not follow Mendelian inheritance patterns.

 

Mendelian patterns of inheritance include one of four modes: autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. The approximate rate of mendelian disorders in humans is 1%. Mendelian genetics allows for specific patterns of inheritance controlled by a single gene pair (“monogenic”).

Lietman et al report that addition of a peptide nucleic acid (PNA) primer to the PCR testing can better identify the mutant GNAS alleles in DNA from peripheral blood cells from patients with McCune-Albright syndrome and fibrous

dysplasia.

 

Leet et al performed a survey study of 20 patients with polyostotic fibrous dysplasia and found that the loss of the normal femoral neck-shaft angle and the disease burden in the lower extremities appear to have the greatest effect on functional activity.

Illustration A shows a case of x-linked recessive pattern of inheritance. Incorrect Answers:

Answer 1: Achondroplasia is autosomal dominant Answer 2: Diastrophic dysplasia is autosomal recessive

Answer 4: Marfan's syndrome is autosomal dominant Answer 5: Gaucher's disease is autosomal recessive

 

298. A decrease in alkaline phosphatase would most likely be manifest in which metabolic disorder?

 

1. Familial hypocalciuric hypercalcemia
2. Hypophosphatasia
3. X-linked hypophosphatemia
4. Secondary hyperparathyroidism
5. Tertiary hyperparathyroidism

 

Corrent answer: 2

 

A decrease in tissue non-specific alkaline phosphatase (TNSALP) is found in hypophosphatasia.

TNSALP is found in osteoblasts and hydrolyzes inorganic phosphates, leading to an increase in serum phosphate levels, which helps to maintain physiologic levels. A decrease in this process impairs bone mineralization leading to rickets. In the perinatal period, hypophosphatasia and decreased

mineralization leads to caput membraneceum, shortened limbs and respiratory failure. Childhood hypophosphatasia is marked by premature loss of deciduous teeth and rachitic deformities. Adult hypophosphatasia I is characterized by teeth and chest wall deformities (similar to adolescent hypophosphatasia) as well as recurrent metatarsal and femoral stress fractures.

Mornet reviewed hypophosphatasia and the alkaline phosphatase mutations. Screening for the 65 distinct mutation can aid in diagnosis and family counseling in severe forms.

 

Illustration A shows abnormal dentition found in hypophosphatasia. Illustration B shows widespread rachitic changes characteristic of hypophosphatasia.

 

Incorrect Answers:

Answers 1, 3, 4, 5: Patients with these conditions have elevated alkaline phosphatase.

 

299. Figure A displays a schematic of the zones of articular hyaline cartilage. Which of the following zones has been shown to contain articular cartilage progenitor cells?

 

1. A
2. B
3. C
4. D
5. E

 

Corrent answer: 1

Articular cartilage progenitor cells (chondrocyte stem cell population) have been identified in the surface zone (superficial tangential zone) of cartilage.

 

Articular cartilage can be divided into different layers, or zones, at various depths that are based on collagen orientation, chondrocyte organization, and proteoglycan distribution.

The superficial tangential zone has collagen fibers and disk-shaped chondrocytes paralleling the articular surface and they have a low proteoglycan concentration, high collagen, and high water concentrations.

 

Dowthwaite et al. used fibronectin in an in vitro differential adhesion assay to identify and describe articular cartilage progenitor cells. They were able to isolate articular cartilage progenitor cells from the surface zone of articular cartilage.

 

Illustration A demonstrates the histology of the articular cartilage layers with H&E staining.

Incorrect Answers:

2: Middle zone

3: Deep zone

4: Lamina splendens

5: Tidemark

 

300. How does a dynamic compression plate achieve compression at the fracture of a long bone?

 

1. Eccentric placement of a cortical screw into a hole in the plate
2. Placing a cortical screw in lag fashion by overdrilling the near cortex
3. Locking of the head of the screw into a threaded hole in the plate
4. Concentric placement of a cortical screw into the center of the hole in the plate
5. The plate allows secondary healing of bone and does not acheive compression at the fracture site

 

Corrent answer: 1

 

Dynamic compression plates achieve compression through eccentric placement of a cortical screw into an oval hole in the plate. During the final tightening of the screw, the screw head will be forced into the center of the hole squeezing the fracture together beneath the plate. This creates compression at the

fracture site. Dynamic compression is ideal for transverse fractures that are not suitable for lag screw compression.

 

Incorrect Answers:

Answer 2: describes lag screw fixation Answer 3: describes locking screw fixation

Answer 4: describes a screw placed into a neutralization plate Answer5: incorrect statement

 

Illustration A is a photo of a dynamic compression plate. Compression is acheived by placing the screw eccentrically into the far side of the plate hole away from the fracture.

 

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