ORTHOPEDICS HYPERGUIDE MCQ 301-350

301. (2001) Q1-2417:

Staphylococcus epidermidis adheres:

1) More strongly to polyethylene

3) Similarly to both polyethylene and alumina ceramic

2) More strongly to alumina ceramic

5) More strongly to polymethylmethacrylate

4) This has not been studied in a laboratory setting.

Staphylococcus epidermidis adheres 2.5 times more strongly to high density polyethylene than alumina ceramic

■Correct Answer: More strongly to polyethylene

302. (2002) Q1-2418:

The wear rate of ceramic-ceramiCbearings in total hip arthroplasty is:

1) 0.05 to 0.06 mm/year

3) 0.03 to 0.02 mm/year

2) 0.04 to 0.05 mm/year

5) Too small to measure

4) 0.01 to 0.02 mm/year

The wear rate of ceramic-ceramiCbearing surfaces in a 10-year follow-up was observed to be 0.01 mm/year

■Correct Answer:

0.01 to 0.02 mm/year

303. (2003) Q1-2419:

Which of the following observations concerning metal-metal prostheses is not true:

1) Low incidence of osteolysis

3) There is a theoretical concern of cancer

2) There is concern about increased metal ions in the body

5) High incidence of osteolysis

4) Hypersensitivity

The controversies with metal-metal total hip replacement relate to increased metal ions. In Europe, Hans Willert reported a 0.5%

prevalence of hypersensitivity to metal-metal (personal communication, January 2001).

One advantage of metal-on-metal total hip replacement is a low incidence of osteolysis. Osteolysis in the cemented cup and the modular cup series has been better than that observed with standard polyethylene acetabular components.

There also is a theoretical concern of cancer. The 20-year studies from Scandinavia (particularly Finland) have not found any positive correlation to cancer

■Correct Answer: High incidence of osteolysis

304. (2004) Q1-2420:

The best predictor for the necessity of blood transfusion in total knee replacement is:

1) Preoperative hemoglobin

3) Use of a hemovac

2) Operative time

5) Surgical approach

4) Rheumatoid arthritis

The biggest predictor for transfusion is the preoperative hemoglobin. There is a 69% chance of an allogeniCtransfusion if the hemoglobin is less than 13 g/dL and only a 13% chance if more than 15 g/dL

■Correct Answer: Preoperative hemoglobin

305. (2005) Q1-2421:

A patient undergoing a total knee replacement with a preoperative hemoglobin >15 g/dL has what chance of requiring a transfusion:

1) 5%

3) 20%

2) 10%

5) 40%

4) 30%

There is a 69% chance of an allogeniCtransfusion if the hemoglobin is less than 13 g/dL and only a 13% chance if more than 15 g/dL. A surgeon must weigh the risks when lowering the preoperative hemoglobin below this level with autologous donation 1 or 2 weeks before surgery

■Correct Answer: 10%

306. (2006) Q1-2422:

The most effective method of reducing deep infection in total joint replacement is:

1) AntibiotiCbone cement

3) SystemiCantibiotics

2) AntibiotiCbone cement plus systemiCantibiotics

5) Adequate skin preparation

4) No antibiotics

The use of antibiotiCbone cement plus systemiCantibiotics is the most effective strategy in reducing deep infection. This is followed by the use of systemiCantibiotics alone, antibiotiCbone cement alone, and no antibiotics

■Correct Answer: AntibiotiCbone cement plus systemiCantibiotics

307. (2007) Q1-2423:

Which of the following bone cements is associated with the lowest risk ratio for revision hip surgery:

1) Sulfix

3) CMW

2) Simplex

5) Palacos gentamicin

4) Palacos

Malchau and colleagues also performed Poisson modeling, assessing the risk of deep infection in revision surgery using different types of bone cement. Using Sulfix bone cement (Sulzer, Winterhur, Switzerland) as the numerator, the investigators assessed Simplex (Stryker Howmedica Osteonics, Allentown, NJ), CMW (Johnson & Johnson DePuy, Warsaw, Ind), Palacos (Merck/Biomet, Warsaw, Ind), and Palacos gentamicin (Merck/Biomet) bone cements. They developed a risk ratio for revision using any of these bone cements. Palacos gentamicin bone cement was associated with the lowest risk ratio for revision

■Correct Answer: Palacos gentamicin

308. (2316) Q1-2769:

Early catastrophiCfailure of the precoat stem was due to:

1) A thin cement mantle

3) Excessive residual bone

2) Use of low viscosity cement

5) Proximal debonding associated with laser etching of the identifying numbers and letters on the stem

4) Proximal debonding

The catastrophiCfailure of the precoat stem was due to proximal debonding associated with laser etching of the identifying numbers and letters on the stem of the prosthesis. Virtually all reported stem failures occurred in left hips because the laser etching caused a local stress concentration effect on the higher stress anterior surface

■Correct Answer: Proximal debonding associated with laser etching of the identifying numbers and letters on the stem

309. (2322) Q1-2776:

Mallet injuries with greater than      percent of the articular surface involved and palmar subluxation as a result will most likely require surgical intervention:

1) 30

3) 10

2) 70

5) 90

4) 50

Type IVCinjuries include distal phalanx base fractures involving more than 50% of the articular surface. Most surgeons feel that accurate reduction is mandatory to prevent joint deformity, secondary arthritis, and stiffness

■Correct Answer: 50

310. (2432) Q1-2893:

Slide 1

A 70-year-old man has difficulty ambulating following a knee replacement. The lateral radiograph of the knee is shown (Slide). The most likely cause of the disability is:

1) Lateral patellar instability

3) Quadriceps tendon rupture

2) Patellar tendon rupture

5) Axial instability

4) Flexion instability

Patients may present with severe knee pain after a mild traumatiCevent. Patients may have the inability to extend the knee or walk. Laxity in flexion (flexion instability) can result in dislocation of the femorotibial articulation. The cam of the femoral component rides up and over the top of the post of the tibial polyethylene insert. The dislocation is usually the result of a traumatiCepisode.

Flexion instability occurs in about 1% to 2% of knee replacements when the knee is not properly balanced following a replacement. The extension and flexion gap must be equal. When balancing a knee, especially one that is tight in extension, the surgeon may choose to place a smaller tibial polyethylene component to achieve full extension with resulting instability of the knee in flexion because the knee flexion gap is larger than the polyethylene insert.

Treatment of flexion instability in posterior stabilized knee replacements can be nonoperative with casting or bracing initially. Two- thirds of patients can be managed successfully nonoperatively. If symptoms persist, revision to a larger polyethylene component can be very effective. If the knee remains unstable, revision to a more constrained prosthesis may be necessary

■Correct Answer: Flexion instability

311. (2433) Q1-2894:

While performing posterior cruciate sacrificing knee replacement surgery, the surgeon notes a 15° flexion contracture during trial reduction after the bone cuts and soft tissue balancing. The best option is:

1) Placement of a smaller polyethylene insert

3) Resection of additional bone from the distal femur

2) Resection of additional bone from the proximal tibia

5) Accepting the contracture and applying an extension cast postoperatively

4) Resection of additional bone from the proximal tibia and distal femur

This is a common problem. Selection of a smaller polyethylene spacer results in a correction of the flexion contracture but also results in flexion instability as the flexion gap will be larger than the extension gap. First, surgeons should remove any posterior osteophytes from the distal femur. Second, the posterior capsule should be incised. If both of these maneuvers fail to correct the contracture, the surgeon should remove additional bone from the distal femur. The joint line may be raised up to 8 mm when performing posterior stabilized arthroplasties without compromising the result

■Correct Answer: Resection of additional bone from the distal femur

312. (2434) Q1-2895:

When performing total knee replacement surgery, the following statement is true:

1) The distal femoral cut only effects the extension gap.

3) The proximal tibia cut only effects the flexion gap.

2) The proximal tibia cut only effects the extension gap.

5) The posterior femoral condyle cut effects the flexion and extension gaps.

4) The distal femoral cut only effects the flexion gap.

These are important concepts when balancing the knee following total knee replacement.

The distal femoral cut only effects the extension gap.

The proximal tibia cut effects the flexion and extension gaps. The posterior femoral condyle cut effects the flexion only.

Attention to these principles is very important to prevent both contractures and flexion instability. Correct Answer: The distal femoral cut only effects the extension gap.

313. (2435) Q1-2896:

While performing revision total knee arthroplasty, the surgeon notices a flexion gap that is larger than the extension gap. The following statement is most likely true:

1) The femoral component is probably too large.

3) There is inadequate distal femoral augmentation.

2) There is posterior translation of the femoral component.

5) There is excessive thickness of the distal femoral augmentation blocks.

4) There is excessive thickness of the patellar component.

Flexion instability is common following revision total knee replacement. The following principles are important:

Undersizing the femoral component is common. This occurs secondary to the posterior femoral condyle bone loss.

Anterior translation of the femoral component increases the flexion gap. The use of posterior femoral condyle augments or an offset stem can solve this problem.

Distal femoral augments that are too thick will narrow the extension gap. One should set the joint line approximately 25 mm to 30 mm below the epicondylar axis.

Excessive size of the patellar component will restrict knee flexion, however, it will not change the flexion and extension gaps. Correct Answer: There is excessive thickness of the distal femoral augmentation blocks.

314. (2436) Q1-2897:

The stem associated with the highest incidence of osteolysis is the:

1) Proximal coated femoral stem

3) Fully coated femoral stem

2) Distal coated femoral stem

5) Cemented femoral stem

4) Patch-porous coated femoral stem

The noncircumferentially  coated titanium alloy patch-porous coated straight Harris-Galante stem was associated with significant osteolysis, thigh pain, subsidence, and endosteal erosion. The patched porous coating is believed to allow ingress of joint fluid and wear debris into the endosteal canal, increasing the effective joint space

■Correct Answer: Patch-porous coated femoral stem

315. (2437) Q1-2898:

During controlled perforation for removal of stem and prosthesis, when making 9-mm holes in the femoral diaphysis:

1) The size of the hole should be 20% of the diameter of the shaft

3) The size of the hole should be 60% of the diameter of the shaft

2) The size of the hole must not exceed 30% of the diameter of the shaft

5) The holes must be in the posterolateral surface of the femur

4) Two holes must be one hole diameter apart

The size of the hole must not exceed 30% of the diameter of the shaft. Holes should not be placed any closer than two hole diameters apart, and they should be located in the anterolateral surface of the femur to decrease the stress riser

■Correct Answer: The size of the hole must not exceed 30% of the diameter of the shaft

316. (2438) Q1-2899:

The gold standard for the diagnosis of avascular necrosis of the femoral head is:

1) Bone scan

3) MagnetiCresonance image

2) Routine roentgenogram

5) Elevated sedimentation rate

4) Segmented bone collapse

The gold standard for the diagnosis of avascular necrosis is magnetiCresonance imaging. Changes can be seen earliest with this technique before there are changes on routine roentgenogram and even before a patient is symptomatic

■Correct Answer: MagnetiCresonance image

317. (2439) Q1-2900:

The low incidence of infection in ceramic-ceramiCtotal hip replacement is:

1) True only in early infection

3) Has not been reported in the literature and is only anecdotal

2) True only in late infection

5) True because bacteria adhere more strongly to polyethylene

4) True because bacteria adhere more strongly to ceramic

There is a lower incidence of infection reported in ceramic-ceramiCtotal hip replacements by the Swedish Hip Registry. This may

be related to the fact that bacteria typically adhere more strongly to polyethylene than cement, suggesting that both early and late infection may be lower for alumina than polyethylene total hip replacement

■Correct Answer: True because bacteria adhere more strongly to polyethylene

318. (2440) Q1-2901:

The first step in the development of hip osteoarthritis is:

1) Abnormal glycosaminoglycans

3) Abnormal weight gain

2) Formation of ganglions

5) Abnormal mechanical stress

4) Fatiguing of labrum under normal stress

The first step toward osteoarthritis of the dysplastiChip is fatiguing of the labrum under normal stress. Klaue et al described the different pathomorphologies from a torn labrum to ganglion formation, which has been attributed to acetabular rim syndrome

■Correct Answer: Fatiguing of labrum under normal stress

319. (2462) Q1-2927:

The common iliaCartery gives rise to all of the following vessels except:

1) The external iliaCartery

3) The superior gluteal artery

2) The internal iliaCartery

5) The internal hypogastriCartery

4) The common femoral artery

The common iliaCartery divides at the L5-S1 vertebral disk. The anterior division, the external iliaCartery, continues distally to become the common femoral artery, whereas the posterior division becomes the internal iliaCartery. The internal iliaCartery branches again into a posterior division, which gives rise to the superior gluteal artery, and an anterior division, which gives off the obturator artery before dividing into the inferior gluteal artery and internal pudendal artery

■Correct Answer: The internal hypogastriCartery

320. (2463) Q1-2928:

The structure at highest risk for injury in total hip arthroplasty (THA) is the:

1) Femoral artery

3) External iliaCartery

2) Femoral vein

5) Obturator artery

4) Inferior gluteal artery

The external iliaCartery and vein are immobile and lie close to the pelvis, and thus are at high risk for injury in THA. The external iliaCvein lies within 7 mm of the anterior column of the pelvis at the anterior inferior iliaCspine and within 4 mm at the acetabula dome. The external iliaCartery is at less risk due to its thicker intima and increased distance from the bone. The external iliaCartery lies within 10 mm of the bone at the anterior inferior iliaCspine and within 7 mm at the acetabular dome. The common femoral artery lies anterior and medial to the hip capsule. Only the iliopsoas lies between the vessel and capsule at this point. The femoral vein lies medial to the artery and is not likely to be injured. The obturator vessels are also at risk, lying fixed within 1 mm of the bony surface at the quadrilateral surface, with their only protection being the interposition of the obturator internus muscle

■Correct Answer: External iliaCartery

321. (2464) Q1-2929:

The nerve most commonly injured during total hip arthroplasty (THA) is the:

1) Superior gluteal nerve

3) Femoral nerve

2) Obturator nerve

5) Peroneal component of sciatiCnerve

4) Inferior gluteal nerve

The primary nerves of the region are the sciatic, femoral, inferior and superior gluteal, and obturator. The most common nerve injury during THA is to the peroneal division of the sciatiCnerve, followed by superior gluteal, obturator, and femoral nerves. Injury to these structures can lead to loss of function and poor outcomes

■Correct Answer: Peroneal component of sciatiCnerve

322. (2465) Q1-2930:

Which two quadrants of the acetabulum are most at risk for injury by screws during fixation of total hip arthroplasty (THA):

1) Anterior-superior and posterior-inferior

3) Anterior-superior and posterior-superior

2) Posterior-superior and posterior inferior

5) Anterior-superior and anterior-inferior

4) Anterior-inferior and posterior-superior

The acetabular quadrant system described by Wasielewski and colleagues is useful for determining the location of planned acetabular screw fixation in THA to avoid neurovascular complications. The quadrants are formed by drawing a line from the anterior-superior iliaCspine through the center of the acetabulum and bisecting that line at the center of the acetabulum to form four equal quadrants. The line from the anterior-superior iliaCspine to the center of the acetabulum serves as the dividing line between anterior and posterior, and the bisecting line as the division between superior and inferior.

In cadaver studies, the posterior-superior and posterior-inferior quadrants were shown to have the thickest bone and best potential for obtaining secure fixation with the least risk for injury to vessels. The anterior-superior quadrant (the quadrant of death) and the anterior-inferior quadrant were shown to be the most dangerous quadrants for fixation due to the thin bone and close proximity of the vessels to bone in that region

■Correct Answer: Anterior-superior and anterior-inferior

323. (2466) Q1-2931:

What is the most commonly used surgical approach to the acetabulum:

1) Posterior

3) Anterior

2) Ilioinguinal

5) Anterolateral

4) Medial

The posterior approach to the acetabulum is the least technically demanding approach for total hip arthroplasty (THA) and offers good visualization of the acetabulum, especially of the posterior wall. The posterior approach is the most commonly used approach for THA in the United States. Patients are placed in the lateral position. The approach involves splitting of the gluteus maximus in line with its fibers and no internervous plane is present. The sciatiCnerve is protected by the short external rotators after they are detached from their insertions on the femur and reflected medially

■Correct Answer: Posterior

324. (2467) Q1-2932:

In the ilioinguinal approach, what does the first window allow access to:

1) PelviCbrim and superior pubiCramus

3) Inferior pubiCramus and sciatiCnotch

2) Quadrilateral plate and retropubiCspace

5) Anterior sacroiliaCjoint, internal iliaCfossa, and upper anterior column

4) Ilioschial tuberosity and retropubiCspace

The ilioinguinal approach provides improved visualization of the pelviCinner surface and anterior column and medial wall of the acetabulum. The patient is placed supine or in a lazy lateral decubitus position. The principle of this approach is to dissect closely along the inner wall of the pelvis and lift each muscular and neurovascular structure off of the bone. Three windows are present in this approach, each providing access to different structures. The first window allows access to the anterior sacroiliaCjoint, internal iliaCfossa, and upper anterior column

■Correct Answer: Anterior sacroiliaCjoint, internal iliaCfossa, and upper anterior column

325. (2468) Q1-2933:

The most sensitive method for identifying and quantifying the extent of osteolysis is:

1) Plain radiographs

3) Technetium-99m bone scanning

2) MagnetiCresonance imaging

5) Helical computed tomography

4) Computed tomography

If extensive osteolysis is suspected, computed tomography is recommended because plain radiographs underestimate the extent of lysis. Helical computed tomography with metal artifact minimization is the most sensitive method for identifying and quantifying the extent of lysis

■Correct Answer: Helical computed tomography

326. (2469) Q1-2934:

The most common cause of vascular injury during total hip arthroplasty (THA) is:

1) Laceration

3) Arteriovenous fistula

2) Pseudoaneurysm

5) ThromboemboliCphenomena

4) True aneurysm

A previous review of vascular injuries sustained during THA revealed the most common etiology of vascular injury as thromboemboliCphenomena, followed by laceration, pseudoaneurysm, and arteriovenous fistula

■Correct Answer: ThromboemboliCphenomena

327. (2470) Q1-2935:

The most common cause of damage to femoral vessels is:

1) Extruded cement

3) Capsule dissection

2) Migration of the acetabular cup

5) Screw placement

4) Aberrant retractor placement

Damage to the femoral vessels is most commonly due to aberrant retractor placement. Care should be taken to ensure that the retractor tip is placed directly on bone, and that the iliopsoas is not interposed between the retractor tip and bone. Extruded cement, acetabular cup migration, and capsule dissection have also been implicated in damage to the femoral vessels

■Correct Answer: Aberrant retractor placement

328. (2471) Q1-2936:

The risk of nerve injury following revision total hip arthroplasty (THA) is approximately:

1) 0.5%

3) 1% to 10%

2) 1%

5) More than 20%

4) 10% to 20%

Following primary THA, the incidence of nerve palsy is reported to be approximately 1.3%, but may be as high as 5.2% for primary THA performed for developmental dysplasia or dislocation. For revision surgery, the incidence may be as high as

7.60%

■Correct Answer: 1% to 10%

329. (2472) Q1-2937:

Slide 1

The most likely underlying diagnosis in this patient is:

1) Gout

3) HeterotopiCossification

2) Rheumatoid arthritis

5) Synovial chondromatosis

4) Pigmented villonodular synovitis

This radiograph presents a Brooker class IV heterotopiCossification in a 79-year-old woman after revision of a monopolar hemiarthroplasty to a press-fit, porous-coated acetabular component and a cemented femoral stem. The patient sustained a cerebrovascular accident 12 weeks before surgery. She had no other risk factors for heterotopiCossification formation after total hip arthroplasty. Other risk factors for heterotopiCossification include previous surgery, men with hypertrophiCosteoarthritis, traumatiCbrain injury, spinal hyperostosis, and posttraumatiCarthritis

■Correct Answer: HeterotopiCossification

330. (2473) Q1-2938:

This radiograph is most typical of:

1) Stress fracture

3) Osteitis pubis

2) Osteocarcinoma

5) Ewing's sarcoma

4) Osteomyelitis of the pubiCsymphysis

Osteomyelitis of the pubiCsymphysis is a rare condition, accounting for less than 1% of all acute hematogenous osteomyelitis cases. The condition is well described in elderly patients following urologic, gynecologic, and pelviCprocedures. Osteomyelitis of the pubiCsymphysis has also been reported in intravenous drug abusers, after cardiaCcatheterization, and can occur spontaneously in athletes and children

■Correct Answer: Osteomyelitis of the pubiCsymphysis

331. (2474) Q1-2939:

Which of the following symptoms is least common in patients with osteomyelitis of the pubis:

1) Distal anterior pelviCpain

3) Rectus muscle spasm

2) Adductor muscle spasm

5) Wide-based waddling gait

4) Abductor muscle spasm

Osteomyelitis of the pubiCsymphysis is a rare condition, occurring in 2% to 11% of all patients with osteomyelitis of the pelvis. The osteitis pubis is the least affected area. Signs and symptoms of osteomyelitis of the pubiCsymphysis include distal anterior pelviCpain, adductor and rectus muscle spasms, and a wide-based waddling gait. Fever, leukocytosis, elevated erythrocyte sedimentation rate, and positive blood cultures may also be present. Unilateral rarefaction and sclerosis with cystiCchanges may be seen on radiographs 10 to 14 days after symptoms begin. Radionucleotide scans, computed tomography, and magnetiCresonance imaging may aid in the diagnosis

■Correct Answer: Abductor muscle spasm

332. (2475) Q1-2940:

Common risk factors associated with extensor mechanism disruption after total knee arthroplasty (TKA) include all of the following except:

1) Limited preoperative range of motion

3) Medial parapateller exposure

2) Difficult surgical exposure

5) Obesity

4) Disruption of vascular supply to the patella

The etiology of extensor mechanism disruption after TKA is unknown. Researchers suggest that disruption of the vascular supply to the patella and patellar mechanism during the exposure may cause weakening of the patella and extensor mechanism. In addition, the frequency of extensor mechanism disruption has been reportedly increased in patients who have a preoperative limited range of motion or difficult surgical exposure

■Correct Answer: Medial parapateller exposure

333. (2476) Q1-2941:

Contributing factors causing female athletes to have more anterior cruciate ligament injuries than men include all of the following except:

1) Intercondylar notch width

3) Increased quadriceps angle

2) Ligament size

5) Fitness level

4) Strong overactive hamstrings

Female athletes are two to eight times more likely than men to sustain an anterior cruciate ligament injury when playing sports such as soccer, basketball, and volleyball. The exact etiology of gender-based injuries is unclear. Various intrinsiCfactors (intercondylar notch width, ligament size, quadriceps angle, joint laxity, hormonal effects) and extrinsiCfactors (muscular strength/weakness, fitness level, hamstring:quadriceps  ratio) have been proposed as contributing factors. A strong hamstring actually protects the anterior cruciate ligament and is a preventative measure

■Correct Answer: Strong overactive hamstrings

334. (2477) Q1-2942:

The best results of hip fracture repair occur:

1) In the first 6 hours

3) Within the second day

2) Within the first day

5) Three days after repair

4) Within the third day

Medical consequences of time issues relevant to hip fractures have been examined by several authors. Operation within the first day of injury is superior and provides better results than delaying the procedure. However, the economiCconsequences of such a delay have not been examined

■Correct Answer: Within the first day

335. (2478) Q1-2943:

Slide 1

This T2-weighted sagittal magnetiCresonance image of a right knee reveals:

1) Avascular necrosis of the distal femur

3) Anterior cruciate ligament rupture

2) Synovial sarcoma

5) Popliteal cyst

4) Posterior cruciate ligament rupture

Baker's or popliteal cyst, described first by Adams and later by Baker, is a distended bursa originating posterior to the medial head of the gastrocnemius muscle or semimembranous tendon and generally presents with posterior knee pain and a palpable mass. This case is unusual in that the dissection was proximal, unlike the typical distal progression of the popliteal cyst

■Correct Answer: Popliteal cyst

336. (2479) Q1-2944:

What is the main characteristiCshift in the outcome assessment of total hip arthroplasty (THA) in the past decade:

1) Description of more technical details

3) Introduction of more hip prosthesis designs

2) Analysis and measurement of the impact and longevity of the procedure on a patient's quality-of-life

5) Decreasing number of dislocations

4) Introduction of new functional scoring systems

Over the past two decades, a continuous shift toward outcome assessment in medicine has occurred. Publications previously devoted to technical details and surgical technique have started analyzing and measuring the impact and longevity of medical procedures on patients' quality-of-life and have compared the cost-effectiveness of different procedures

■Correct Answer: Analysis and measurement of the impact and longevity of the procedure on a patient's quality-of-life

337. (2480) Q1-2945:

In the study design for evaluating the effectiveness of total hip replacement, the endpoint can be only:

1) Revision hip surgery

3) Any well-defined chosen point, such as revision hip surgery or functional level and pain

2) RadiographiCloosening of the implant

5) Range of motion

4) Pain or functional level

In the study design, it is paramount that a universal, well-defined endpoint is chosen. In the well-established Scandinavian Hip Registries, this endpoint is revision total hip arthroplasty. Whether this endpoint is sensitive enough is debatable. For more in- depth studies, several other endpoints, such as pain or postoperative functional level, may also be used

■Correct Answer: Any well-defined chosen point, such as revision hip surgery or functional level and pain

338. (2481) Q1-2946:

The single most important criterion to identify the type of hip implant for future analysis in a hip arthroplasty register is:

1) The name of the manufacturer and the year of implant production

3) The implant's catalogue number provided by the manufacturer

2) The name of the implant and the year of implant production

5) The surgeon's name and implant manufacturer

4) The name of the manufacturer and implant

For the implanted prosthesis, manufacturer, name, material, and catalogue numbers are essential for precise future identification. The role of the catalogue numbers cannot be underestimated as successive generations of implants were put on the market with the same brand name (eg, Charnley hip). Without recording the catalogue numbers, it is impossible to determine what generation of implant is being compared to another

■Correct Answer: The implant's catalogue number provided by the manufacturer

339. (2482) Q1-2947:

The main advantage of multicenter studies in analyzing total hip arthroplasty is:

1) The inclusion of different surgeons

3) The ability to obtain a large number of patients

2) The inclusion of different countries

5) Giving more accurate data

4) The inclusion of different hip implants

The main advantage of multicenter studies - although they are time-consuming, expensive, and often frustrating - is obtaining large numbers of patients in a relatively short time. This is important when examining statistical differences between varying results

■Correct Answer: The ability to obtain a large number of patients

340. (2483) Q1-2950:

When comparing viral vectors with nonviral vectors for gene delivery, the advantages of nonviral vectors include all of the following except:

1) Safety

3) More efficiency

2) Less immunogenicity

5) Special packaging cell lines

4) Easier production

Because of the safety concerns, immunogenicity issues, and production complications associated with viral vectors, nonviral delivery systems were developed by complexing of genes (DNA) to various chemical formulations. Nonviral delivery systems stabilize DNA and increase its uptake and include plasmids, peptides, cationiCliposomes, DNA-ligand complexes (recognize

specifiCcell-surface receptors, leading to receptor-mediated uptake), and gene gun (particles of gold coated with DNA, forced into the cells with high velocity bombardment). However, nonviral vector efficiency is lower than viral vectors

■Correct Answer: More efficiency

341. (2484) Q1-2951:

All of the following have been used as viral vectors for gene delivery except:

1) Adeno-associated virus

3) Herpes simplex virus

2) Rotavirus

5) Retroviral vector

4) Lentivirus

A retroviral vector derived from the Moloney murine leukemia retrovirus is among the best-developed viral vectors. Other viral vectors include adenovirus, adeno-associated virus, and herpes simplex virus. Novel vector systems based on lentivirus, which is a type of retrovirus that includes human immunodeficiency virus, are being developed

■Correct Answer: Rotavirus

342. (2485) Q1-2952:

The principle of homologous recombination in gene therapy is used to:

1) Replace a defective gene by a wild-type gene

3) Supplement a wild-type gene

2) Suppress the expression of a mutant gene

5) Replace a defective gene by a normal gene

4) Alter the expression of a mutant gene

Novel approaches to treating genetiCdiseases involve gene repair or replacement rather than gene supplementation. One such approach is based on the principle of homologous recombination (replacement of a defective gene by a normal gene)

■Correct Answer: Replace a defective gene by a normal gene

343. (2486) Q1-2953:

The virus associated with the most immune reactions is:

1) Adeno-associated virus

3) Adenovirus

2) Gutted adenovirus

5) Herpes simplex virus

4) Retrovirus

Adenoviral vectors can cause inflammatory reaction due to immune activation, an event linked to the first death related to gene therapy. This occurred in September 1999 at the University of Pennsylvania in a clinical trial in which an 18-year-old patient received infusion of more than a trillion adenoviral vectors directed to his liver, which triggered a systemiCinflammatory response that became uncontrollable, leading to organ failure and death. Newer-generation gutted or gutless adenovirus vectors are nonimmunogenic

■Correct Answer: Adenovirus

344. (2487) Q1-2954:

Compared with the ex vivo gene delivery system, the in vivo system is:

1) Technically complex

3) Safer

2) Target specific

5) More invasive

4) Less invasive

Two basiCstrategies exist for gene delivery. Direct, or in vivo, gene therapy involves direct introduction of vectors into the body. Indirect, or ex vivo, gene therapy involves removal of target cells from the body, vector introduction by incubation of the cells in vitro, and reimplantation. The in vivo system is less invasive

■Correct Answer: Less invasive

345. (2488) Q1-2955:

The gene that has been studied in greatest detail for application in osteoarthritis is:

1) p53

3) Tissue inhibitors of metalloproteinases-4

2) Interleukin (IL)-13

5) Bone morphogenetiCprotein-2

4) IL-1 receptor antagonist

Gene therapy has been suggested as a means of delivering sustained therapeutiClevels of anti-arthritis gene products to diseased joints. Local gene delivery to the synovial tissue is the approach of choice for osteoarthritis and other conditions affecting a few joints. Gene therapy is less suited to address the extra-articular components of systemiCconditions, such as rheumatoid arthritis.

The gene that has been studied in greatest detail encodes the human IL-1 receptor antagonist. Correct Answer: IL-1 receptor antagonist

346. (2489) Q1-2956:

The osteoinductive potential of LIM mineralization protein (LMP)-1 gene has been studied for clinical application in:

1) Fracture repair

3) Cartilage regeneration

2) Spinal fusion

5) Meniscal injury

4) Ligament healing

Identification of LMP-1, a novel intracellular protein, is a step forward in osteoinductive proteins. Unlike bone morphogenetiCprotein, which is a secreted protein that binds to cell-surface receptor to initiate a response, LMP-1 is an intracellular signaling molecule. Boden and colleagues transfected bone marrow cells from rats ex vivo with LMP-1 gene using DNA plasmid vector and used them during posterior thoraciCand lumbar spinal fusion in rats

■Correct Answer: Spinal fusion

347. (2490) Q1-2957:

The gene studied for application in osteoporosis and wear-induced osteolysis is:

1) Osteoprotegerin

3) Transforming growth factor-Ã1

2) Bone morphogenetiCprotein

5) Interleukin (IL)-receptor antagonist

4) LIM mineralization protein

Various cytokines and cytokine antagonists hold promise as new therapeutiCagents for osteoporosis. Baltzer and colleagues showed that intramedullary injection of Ad-IL-1Ra gene in a murine ovariectomy model strongly reduced the loss of bone mass. Using a similar model, Bolon and associates studied the effect of adenovirus-mediated transfer of osteoprotegerin, which showed more bone volume with reduced osteoclast numbers in axial and appendicular bones after 4 weeks compared with sham-operated mice

■Correct Answer: Osteoprotegerin

348. (2491) Q1-2958:

Gene transfer to a cell using viral vectors is called:

1) Transduction

3) Transformation

2) Transfection

5) Augmentation

4) Conjugation

In vivo gene delivery involves the direct injection of vectors containing the genes into the body with the expectation that they will reach and transduce the target cell. Ex vivo gene delivery is a process whereby the target cells are removed from the body, genetically altered in vitro, and reimplanted into the body

■Correct Answer: Transduction

349. (2492) Q1-2959:

Which of the following genes has been shown to stimulate proteoglycan synthesis for prevention of disk degeneration:

1) LIM mineralization protein

3) Decorin

2) Bone morphogenetiCprotein-7

5) Osteoprotegerin

4) Transforming growth factor (TGF)-Ã1

Intervertebral disk degeneration has been associated with a progressive decrease in proteoglycan content of nucleus pulposus. The potential application of gene therapy for prevention of disk degeneration is to increase or maintain the proteoglycan content of nucleus pulposus. Thompson and colleagues reported that addition of TGF-Ã1 to canine disk tissue in culture stimulated in vitro proteoglycan synthesis

■Correct Answer: Transforming growth factor (TGF)-Ã1

350. (2552) Q1-3024:

The advantages of an arthroscopic-assisted rotator cuff repair include all of the following except:

1) The surgeon can approach the shoulder from multiple angles.

3) Operative time is shorter.

2) The deltoid attachment is preserved.

5) As opposed to other repair methods, a better early range of motion is achieved.

4) Postoperative rehabilitation is accelerated.

Arthroscopy facilitates a thorough assessment and treatment of a rotator cuff tear by approaching the shoulder from multiple angles. It preserves the deltoid attachment to the acromion and postoperative rehabilitation is potentially accelerated if the deltoid does not need to be protected. Arthroscopy achieves a better early range of motion than other repair methods; however, it requires a longer operative time

■Correct Answer: Operative time is shorter.

351. (4054) Q1-3025:

The disadvantages of a complete arthroscopiCrepair of a rotator cuff include all of the following except:

1) Complete arthroscopiCrepair limits some suture configuration options in the tendon.

3) Complete arthroscopiCrepair is technically difficult to perform.

2) Postoperative pain is increased.

5) Operative time is longer.

4) Complex instrumentation is required.

ArthroscopiCrepair techniques generally require the use of suture anchors and limit some suture configuration options in the tendon. Complete arthroscopiCrepair is technically difficult, requires significantly greater and more complex instrumentation, and has a potentially longer operative time. However, it decreases postoperative pain

■Correct Answer: Postoperative pain is increased.