Free Orthopedic MCQs 2022, Nov, 23 | 12:00 am

FREE Orthopedics MCQS 2022 1901.-1950.

FREE Orthopedics MCQS 2022 1901.-1950.

1901. (886) Q5-1154:
Which of the following statements correctly represents the definitions of C hiari I and C hiari II malformations:
1) A C hiari I malformation is displacement of the brainstem through the foramen magnum; a C hiari II malformation also includes the cerebellum.
3) A C hiari I malformation is a cyst in the pons; a C hiari II malformation is a cyst including the cerebellum.
2) A C hiari I malformation is displacement of the cerebellum through the foramen magnum; a C hiari II malformation also includes the brainstem.
5) A C hiari I malformation is a split in the spinal cord; a C hiari II malformation also includes a tight filum terminale.
4) A C hiari I malformation is an absence of the fourth ventricle; a C hiari II malformation also includes the presence of hydrocephalus.
A C hiari I malformation involves displacement of the cerebellum through the foramen magnum. A C hiari II malformation involves similar displacement of the brainstem, as well. In a C hiari II malformation, there is almost always a myelomeningocele in the lower cord. Sometimes a syrinx is also present.
 
■Correct Answer:A C hiari I malformation is displacement of the cerebellum through the foramen magnum; a C hiari II
malformation also includes the brainstem.
1902. (887) Q5-1155:
The conus medullaris is always termed abnormal if it terminates below this level:
1) L1
3) L2
2) L1-2 disk
5) L3
4) L2-3 disk
The vertebral bodies grow faster than the spinal cord. A more caudal placement of the conus medullaris is considered normal in an older patient. However, a conus medullaris below L3 at any age is abnormal and may represent a tethered and/or dysplastic cord.
 
■Correct Answer:L3
1903. (888) Q5-1156:
Regardless of age, the tonsils of the cerebellum should not extend more than this distance below the foramen magnum:
1) 1 mm
3) 3 mm
2) 2 mm
5) Any protrusion is abnormal
4) 5 mm
Displacement of the cerebellar tonsils below the foramen magnum is termed a C hiari malfomation. A C hiari I malformation is an isolated malformation; a C hiari II malformation is associated with a syrinx. Symptoms may include headache, vomiting, and nystagmus. Although the normal protrusion allowed decreases with age, 5 mm is abnormal at any age.
 
■Correct Answer:5 mm
1904. (889) Q5-1157:
When applying a halo, the use of six pins instead of four has which of the following effects:
1) Increase in the infection rate
3) Increased rate of dural puncture
2) Increased rate of pin loosening
5) Increase in risk of injury of the supraorbital nerve
4) Increase in load to failure by 50%
With an increase from four to six pins, the load to failure is increased by more than 50%. Additional pins decrease many of the complications, such as loosening and pin tract infection. The risk of dural puncture is not measurably increased because it is a rare complication.
 
■Correct Answer:Increase in load to failure by 50%
1905. (890) Q5-1158:
Which of the following findings is an indication for the Bernese (Ganz) osteotomy:
1) Acetabular dysplasia in a 10-year-old boy.
3) A 19-year-old man with osteonecrosis (Stulberg-Stage 4) secondary to Perthes disease.
2) A 20-year-old woman with a complete developmental dislocation of the hip.
5) A 35-year-old woman with an AP center-edge angle of 0° and a joint space of 2 mm
4) A 30-year-old woman with an anteroposterior (AP) center-edge angle of 10° and a joint space of 1 mm.
The Bernese (Ganz) osteotomy is contraindicated in patients with open triradiate cartilages because it crosses the cartilage. The procedure is also contraindicated in complete dislocations, incongruous hips, and advanced osteoarthritis with a joint space of 1 mm or less.
 
■Correct Answer:A 35-year-old woman with an AP center-edge angle of 0° and a joint space of 2 mm
1906. (891) Q5-1159:
The false profile radiographic view of the hip is taken with the patient in which of the following positions:
1) The effected hip is against the film and the pelvis is rotated 65° away from the plane of the film.
3) The patient is supine and the beam is angled 45° cephalad.
2) The uneffected hip is against the film and the pelvis is rotated 65° away from the plane of the film.
5) The patient is supine and the affected hip is maximally internally rotated.
4) The patient is supine and the beam is angled 45° caudally.
The false profile radiographic view assesses anterior coverage and is obtained with the affected hip against the film and the pelvis rotated 65° away from the plane of the film.
 
■Correct Answer:The effected hip is against the film and the pelvis is rotated 65° away from the plane of the film.
1907. (892) Q5-1160:
A 15-year-old boy has a history of excessive bleeding when he is cut. His maternal uncle passed away during a tonsillectomy. The boy presents with severe hip pain (worse in extension than in flexion) and some weakness in his knee extension. The most likely cause of the patientâs symptoms is:
1) Septic arthritis of the hip
3) Lumbar epidural hematoma
2) Psoas abscess
5) Hip hemarthrosis
4) Iliopsoas hematoma
The patient has features suggesting mild hemophilia A or B including x-linked inheritance and occasional bleeding episodes. Iliopsoas hematoma is a complication of hemophilia. Bleed into the hip or the lumbar epidural space is less common and there are no signs to suggest infection.
 
■Correct Answer:Iliopsoas hematoma
1908. (893) Q5-1161:
A patient with hemophilia A has a hematoma of the iliopsoas. He has a partial femoral nerve palsy. Treatment involves continuous factor replacement and:
1) Open drainage
3) Percutaneous insertion of a drainage tube
2) Decompression of the fascia over the femoral nerve
5) Observation
4) Embolization of feeder vessels by interventional radiologist
The standard treatment of a psoas abscess is continuous factor replacement. Surgery is usually unnecessary, but it may be considered in cases of acute palsy with severe pain unresponsive to medical therapy. A percutaneous drainage tube is not recommended because the hematoma may be difficult to locate or drain.
 
■Correct Answer:Observation
1909. (894) Q5-1162:
Which of the following best predicts the risk of nonaccidental injury in young children who sustain a fracture of the femur:
1) The fracture pattern
3) The socioeconomic status of the family
2) The location of the fracture
5) C oexistence of other disabilities
4) Whether the child was previously able to walk
Although a spiral fracture is classically consistent with nonaccidental injury, this is not always true. A spiral fracture is often seen in accidental injuries. The location of the fracture in the femur, the socioeconomic status of the family, and the coexistence of other disabilities are all poor predictors. The ability of the child to walk has predictive ability. In one study, nonaccidental injury accounted for 42% of all femur fractures in children before walking age vs. only 2% of fractures after walking age.
 
■Correct Answer:Whether the child was previously able to walk
1910. (895) Q5-1163:
Which of the following is known about the genetics of multiple hereditary exostosis (MHE):
1) There is no genetic pattern for this condition.
3) MHE follows an autosomal recessive pattern.
2) MHE follows an x-linked inheritance pattern.
5) MHE involves a defect in fibroblast growth factor.
4) MHE encodes glycosyltransferases needed for biosynthesis of heparan sulfate.
Multiple hereditary exostosis (MHE) is inherited as an autosomal dominant condition. There are three genes known to be involved: EXT 1, 2, and 3. EXT 1 and 2 encode glycosyltransferases needed for biosynthesis of heparan sulfate. Fibroblast growth factor receptor is abnormal in achondroplasia.
 
■Correct Answer:MHE encodes glycosyltransferases needed for biosynthesis of heparan sulfate.
1911. (896) Q5-1164:
A 10-year-old patient has a painful lytic lesion replacing 75% of the distal femoral metaphysis. The lesion has indistinct margins, but there is not any periosteal reaction. Biopsy reveals a benign histiocytic tumor with multiple eosinophils. Physical exam and skeletal survey reveal no other abnormalities. Which of the following would be the most appropriate treatment method:
1) Radiation therapy
3) Oral prednisone treatment for one month
2) Methotrexate, ifosfamide and adriamycin followed by resection
5) C urettage and bone graft
4) Resection and reconstruction
This patient has an eosinophilic granuloma, which is an isolated form of Langerhans cell histiocytosis. Patients with isolated involvement may be treated with observation, curettage, bone grafting, or steroid injection. For a lesion of this size, the risk of fracture is high and curettage with bone grafting is recommended. C hemotherapy and/or systemic steroids are reserved for patients with systemic disease.
 
■Correct Answer:C urettage and bone graft
1912. (897) Q5-1165:
Which of the following methods has the highest sensitivity in detecting skeletal lesions in patients with Langerhans cell histiocytosis:
1) Physical examination
3) Ultrasound
2) Skeletal survey
5) Indium labeled white blood cell study
4) Bone scan
Skeletal survey is the most sensitive means of detecting lesions of eosinophilic granuloma (Langerhans cell histiocytosis). Bone scan detects most, but not all, of the lesions. Some lesions lack enough osteoblastic activity to appear on bone scan. Lesions are not detected on physical exam unless they are large enough to cause pain or tenderness. Indium labeled white cell studies are not used in this condition.
 
■Correct Answer:Skeletal survey
1913. (898) Q5-1166:
A 15-year-old girl presents with pain and a 17°-scoliosis curve. The film suggests an enlargement and sclerosis of the transverse process of L2. The best study to further evaluate the nature and anatomic extent of the lesion is:
1) C oned radiographs
3) Bone scan with SPEC T (single photon emission computed tomography)
2) Bone scintigraphy
5) C omputed tomography
4) Magnetic resonance imaging
This lesion is most likely to be an osteoid osteoma or an osteoblastoma. The best study to further evaluate the nature and anatomic extent is with computed tomography.
Magnetic resonance imaging may overestimate the lesion because of sensitivity to edema in the marrow and surrounding soft tissue. Bone scintigraphy with or without SPEC T does not provide enough anatomic detail. C oned radiographs do not provide the needed multidimensional detail for this condition, as well as many other spinal problems.
 
■Correct Answer:C omputed tomography
1914. (899) Q5-1167:
Fibrous dysplasia has been determined to be the result of a mutation in which gene:
1) GNAS1
3) FBN1
2) FGFR3
5) C OL1A1
4) C FBA1
Fibrous dysplasia has been determined to be the result of a postzygotic mutation in the GNAS1 (stimulatory G protein of adenylyl cyclase) gene. All of the cells that are descended from the cell with the mutation manifest features of the disease.
FGFR3 (fibroblast growth factor receptor-3 protein) is abnormal in achondroplasia. FBN1 (fibrillin 1) is abnormal in Marfan syndrome.
C FBA1 is abnormal in cleidocranial dysplasia.
C OL1A1 (collagen, type 1, alpha 1) is abnormal in osteogenesis imperfecta. 
■Correct Answer:GNAS1
1915. (900) Q5-1168:
Which of the following conditions is not associated with congenital contractures:
1) Amyoplasia
3) Popliteal pterygium syndrome
2) Diastrophic dysplasia
5) Down syndrome
4) Larsen syndrome
Down syndrome is the only condition listed that does not involve congenital contractures.
Amyoplasia (or classic arthrogryposis) involves multiple contractures with normal intelligence and loss of flexion creases. Diastrophic dysplasia is a disorder of cartilage that includes contractures of many joints, as well as epiphyseal irregularity. Popliteal pterygium syndrome includes contractures with webbing across the flexor surfaces of the joints.
Larsen syndrome involves multiple joint dislocations, as well as contractures. 
■Correct Answer:Down syndrome
1916. (901) Q5-1169:
Diastematomyelia is best described as:
1) Protrusion of neural elements dorsally from the back.
3) Two hemivertebrae at adjacent levels.
2) A duplicated spinal column.
5) A cyst within the spinal cord.
4) An osseous or fibrocartilaginous septum in the spinal canal.
A diastematomyelia is an osseous or fibrocartilaginous septum within the spinal canal that invaginates or splits the neural tissue. A diastematomyelia may or may not be associated with neurologic deficit. Surgical excision is indicated for the presence of symptoms or at the time of spinal deformity correction.
 
■Correct Answer:An osseous or fibrocartilaginous septum in the spinal canal.
1917. (902) Q5-1170:
Diastematomyelia is most common in which region of the spine:
1) C ervical
3) Lower thoracic
2) Upper thoracic
5) Sacral
4) Lumbar
Several series of patients with diastematomyelia have shown the following anatomic distribution: 64% occur in the lumbar spine,
27% occur in the lower thoracic spine, 9% in the upper thoracic spine, and almost none occur in the cervical or sacral regions. 
■Correct Answer:Lumbar
1918. (903) Q5-1171:
Which of the following is the most common finding in diastematomyelia:
1) C utaneous lesions over the spine
3) Foot deformity
2) Anisomelia
5) Widened interpedicular distance
4) Neurologic deficit
Widened interpedicular distance is the most common finding (94% or greater) in patients with diastematomyelia.
Neurologic deficit is present in 60% to 88% of patients with diastematomyelia.
A cutaneous lesion, such as a dimple or hairy patch, is present in 55% to 79% of patients with diastematomyelia. Anisomelia is present in 53% to 58% of patients with diastematomyelia.
Foot deformities are present in 32% to 52% of patients with diastematomyelia. 
■Correct Answer:Widened interpedicular distance
1919. (904) Q5-1172:
In which of the following clinical situations would it be most appropriate to recommend an anterior and posterior hemiepiphyseodesis of the convex side of a congenital scoliosis:
1) A 12-year-old girl with a hemivertebra of L3.
3) A 5-year-old boy with a congenital bar of T3-4.
2) A 10-year-old boy with a hemivertebra of L3.
5) A 5-year-old boy with a hemivertebra of L5.
4) A 5-year-old boy with a hemivertebra of T5.
Hemiepiphyseodesis is most likely to produce progressive curve correction in patients under age 6. Hemiepiphyseodesis is not likely to result in improvement when there is no concave growth potential, as in the case of a congenital bar. In hemivertebra of the lumbosacral region, improvement is most likely when a hemivertebra resection is performed.
 
■Correct Answer:A 5-year-old boy with a hemivertebra of T5.
1920. (905) Q5-1173:
Which of the following is the seating arrangement recommended for a 5-year-old in a family automobile:
1) Lap belt in the middle of the back seat
3) Lap and shoulder belt and booster seat in back
2) Lap and shoulder belt in the back seat
5) Lap and shoulder belt and booster seat in front
4) Rear-facing child seat in back
C hildren ages 4 to 8 (40 lbs to 60 lbs) are at risk for airbag injuries and should not be in the front seat. In addition, they require booster seats to allow proper fitting of the shoulder harness on the upper torso. Rear-facing seats are only appropriate for infants. C hildren should not be in the front seat until after age 12 and over 100 lbs.
 
■Correct Answer:Lap and shoulder belt and booster seat in back
1921. (906) Q5-1174:
Immediate internal fixation of diaphyseal fractures in polytraumatized children has been shown to provide which of the following benefits:
1) Increased survival rate
3) Decreased incidence of deep venous thrombosis
2) Decreased incidence of fat emboli
5) Greater ease of management
4) Improved recovery of central nervous system function after head injury
Acute internal fixation in children has not been shown to provide the same life-saving and morbidity-reducing benefits as in adults. However, it will ease the management of the polytraumatized patient.
 
■Correct Answer:Greater ease of management
1922. (907) Q5-1175:
Which of the following statements is true about pin fixation of supracondylar humerus fractures:
1) Fixation with two lateral pins is biomechanically stronger than crossed pins.
3) Pin fixation is associated with a higher risk of compartment syndrome than cast treatment alone.
2) Fixation with two lateral pins has a higher risk of iatrogenic nerve injury than medial and lateral pins.
5) Use of two medial pins is the most biomechanically stable construct.
4) Fixation with medial and lateral pins carries a higher risk of iatrogenic ulnar nerve injury than two lateral pins.
Pin fixation of supracondylar humerus fractures in children decreases the risk of compartment syndrome as well as malreduction. Use of medial and lateral pins has been shown to be the most stable construct in biomechanical studies. The use of medial and lateral pins carries a risk of iatrogenic injury to the ulnar nerve. No nerve injuries have been demonstrated after the use of two lateral pins.
 
■Correct Answer:Fixation with medial and lateral pins carries a higher risk of iatrogenic ulnar nerve injury than two lateral pins.
1923. (908) Q5-1176:
A 6-year-old boy who is treated for a type III supracondylar fracture has no neurovascular deficit on initial examination. His fracture is treated by anatomic closed reduction and percutaneous fixation with medial and lateral pins. A partial deficit in ulnar motor and sensory function is noted after surgery. The next step in treatment should be:
1) Remove the lateral pin.
3) Explore the ulnar nerve.
2) Remove both pins and place the patient in traction.
5) Make sure the elbow is flexed to no more than 90° and observe.
4) Transpose the ulnar nerve anteriorly.
The use of medial pins in treatment of supracondylar fractures of the humerus has been associated with a risk of ulnar nerve injury. However, in the largest reported series, 16 of 17 palsies resolved spontaneously and completely with observation after a mean of 18 weeks. There is no evidence that pin removal, exploration, or transposition is necessary at this stage. Hyperflexion in a splint may cause the nerve to be apposed to the pin and can be decreased.
 
■Correct Answer:Make sure the elbow is flexed to no more than 90° and observe.
1924. (909) Q5-1177:
Which of the following factors is associated with a decrease in the accuracy of measurement of congenital scoliosis:
1) Increase in the size of the curve
3) Increased level of training in deformity surgery
2) Decrease in the size of the curve
5) Use of the Ferguson technique instead of the C obb technique
4) Film coned and centered on the deformity
Measurement of congenital scoliosis has an intraobserver variation of 8°. Measurement accuracy decreases with decreased level of training, increased curve size, and decreased clarity of the endpoints. A coned and centered film would give better detail.
 
■Correct Answer:Increase in the size of the curve
1925. (910) Q5-1178:
Which of the following structures enables the growth plate to grow in diameter as the skeleton gets larger:
1) The chondroepiphysis
3) The groove of Ranvier
2) The apophysis
5) The secondary spongiosa
4) The ring of LaC roix
The ossification groove of Ranvier contains chondrocytes that provide latitudinal growth of the growth plate. The groove of Ranvier may be thought of as âthe growth ring of the growth plate.â
The chondroepiphysis is the cartilage precursor of the epiphysis. The apophysis is a nonarticular growth region.
The ring of LaC roix is a peripheral structure that reinforces the growth plate. The secondary spongiosa is mature lamellar bone after it has been remodeled.
 
■Correct Answer:The groove of Ranvier
1926. (911) Q5-1180:
Which area of the growth plate has the lowest oxygen tension:
1) The reserve zone
3) The hypertrophic zone
2) The proliferative zone
5) The perichondral ring
4) The zone of calcification
The lowest pressure of oxygen is in the hypertrophic zone because it is poorly vascularized. This is one of the features that triggers cell death and calcificaton.
 
■Correct Answer:The hypertrophic zone
1927. (912) Q5-1181:
How many major centers of ossification comprise the normal lumbar vertebral body:
1) One
3) Three
2) Two
5) Five
4) Four
The normal lumbar and thoracic vertebrae are comprised of two posterior and one main anterior ossification center. These join at the neurocentral synchondrosis and the midline vertebal ossification center.
 
■Correct Answer:Three
1928. (913) Q5-1182:
The somite refers to which of the following features of embryologic development:
1) A group of cells that produce the limb bud
3) A group of cells that differentiate to form the cranium
2) A structure that gives rise to the spinal cord
5) A set of homeobox genes
4) A group of cells that are repeated to form the axial skeleton
The somite is a group of tissues that are bilaterally symmetric and repeated to comprise the axial skeleton. Each somite contains a dermatome, myotome, and sclerotome.
 
■Correct Answer:A group of cells that are repeated to form the axial skeleton
1929. (914) Q5-1183:
Homeobox genes are best characterized by which of the following descriptions:
1) Homeobox genes regulate fracture healing.
3) Homeobox genes are a series of genes that regulate limb genesis.
2) Homeobox genes are involved in immune system regulation.
5) Homeobox genes regulate vascular invasion of the physis.
4) Homeobox genes regulate spinal development.
Homeobox genes code for transcription factors involved in regulation of limb genesis in the embryonic period. Homeobox genes have a highly conserved 60-nucleotide sequence.
 
■Correct Answer:Homeobox genes are a series of genes that regulate limb genesis.
1930. (915) Q5-1184:
Which of the following regions of the physis has the highest degree of proteoglycan aggregation in the matrix:
1) Reserve zone
3) Hypertrophic zone
2) Proliferative zone
5) Metaphysis
4) Zone of degeneration
The proteoglycan aggregation is greatest in the reserve zone and in the epiphysis. Proteoglycan concentration progressively decreases in the direction of the metaphysis. This phenomenon also enables calcification to occur.
 
■Correct Answer:Reserve zone
1931. (4040) Q5-1186:
Which of the following categories of slipped capital femoral epiphysis (SC FE) is associated with the highest rate of bilaterality:
1) Idiopathic SC FE
3) Radiation therapy
2) Renal failure
5) Growth hormone deficiency
4) Hypothyroidism
Renal failure is associated with the highest risk (90%) of bilaterality. By contrast, idiopathic SC FE has a 20% risk of bilaterality initially and a further 10% to 20% risk until maturity.
 
■Correct Answer:Renal failure
1932. (916) Q5-1187:
An African-American mother brings her 18-month-old baby in for examination because he has bowing of the legs. The childâs past medical history is normal including height and weight. The child is still breast-fed. Radiographs reveal mild widening and irregularity of the physes. Which of the following conditions is likely to be found on laboratory examination:
1) Elevated phosphorus
3) Normal 1,25 dihydroxyvitamin D
2) Decreased alkaline phosphatase
5) Elevated parathyroid hormone
4) Elevated creatinine
This patient has nutritional rickets because of a combination of decreased vitamin D intake and increased need for sunlight due to dark skin. The laboratory findings should include a lowânormal calcium phosphate, elevated alkaline phosphatase and parathryoid hormone, and low vitamin D levels and precursors. Vitamin D supplementation without bracing is adequate treatment.
 
■Correct Answer:Elevated parathyroid hormone
1933. (917) Q5-1188:
The dose of acetaminophen for a child should be no more than:
1) 1.5 mg/kg
3) 10-15 mg/kg
2) 5 mg/kg
5) 50 mg/kg
4) 20-30 mg/kg
The dose of acetaminophen should be 10-15 mg/kg. The maximum daily dose should be no more than 75 mg/kg. Larger doses of acetaminophen pose a risk of hepatotoxicity over a long period of time.
 
■Correct Answer:10-15 mg/kg
1934. (918) Q5-1189:
Opioids must be used with caution in infants younger than 3 months of age because of which of the following properties:
1) Increased clearance
3) Increased hepatic activity
2) Increased protein binding
5) Decreased body surface area to mass
4) Decreased clearance and protein binding
Opioids must be used with caution in infants younger than 3 months of age because of decreased clearance and decreased protein binding. This results in greater bioavailability.
 
■Correct Answer:Decreased clearance and protein binding
1935. (919) Q5-1190:
The potency ratio of hydromorphone to morphine sulfate is:
1) 1-2:1
3) 7-10:1
2) 5:1
5) 50:1
4) 20-25:1
The potency ratio of commonly-used drugs is one of the factors that determines the appropriate dose of a drug. The potency ratio of hydromorphone to morphine sulfate is 7-10:1.
 
■Correct Answer:7-10:1
1936. (920) Q5-1191:
The youngest age at which a number scale to quantitate pain (i.e., rating it as 1-10) can be appropriately used is:
1) 2 years
3) 5 years
2) 3 years
5) 9 years
4) 7 years
Pain measurement is becoming increasingly important for both children and adults. A number scale to quantitate pain can be appropriately used for most children over the age of 7 years. For younger children, the âfaces scaleâ or a finger span scale (stretching the fingers as far apart as possible) is more accurate.
 
■Correct Answer:7 years
1937. (921) Q5-1192:
Which of the following findings on a neuromuscular examination is not characteristic of spasticity:
1) Hyperreflexia
3) Velocity-dependent resistance
2) C lonus
5) Muscle contracture
4) Writhing movements
Spasticity is a hallmark of upper motor lesions. Spasticity is characterized by hyperreflexia, clonus, and velocity-dependent resistance. After early childhood, muscle contracture also develops. Writhing movements are characteristic of athetosis, not spasticity.
 
■Correct Answer:Writhing movements
1938. (922) Q5-1193:
Which of the following describes the mechanism of action of Botulinum toxin type A:
1) Botulinum toxin type A blocks the release of acetylcholine.
3) Botulinum toxin type A interrupts transmission of impulses along axons.
2) Botulinum toxin type A prevents binding of acetylcholine to receptors.
5) Botulinum toxin type A depolarizes sarcolemma of muscles.
4) Botulinum toxin type A softens fibrous tissue causing contracture.
Botulinum toxin type A acts by blocking the release of acetylcholine at the nerve terminal. Over time, new terminals sprout and the effect is lost. By contrast, alcohol and phenol denature proteins and disrupt nerve conduction.
 
■Correct Answer:Botulinum toxin type A blocks the release of acetylcholine.
1939. (923) Q5-1194:
Which of the following describes the mechanism of action of baclofen:
1) Baclofen mimics the effect of gamma-aminobutyric acid (GABA).
3) Baclofen binds to actylcholine receptors.
2) Baclofen blocks the effect of GABA.
5) Baclofen inhibits serotonin reuptake.
4) Baclofen potentiates the effect of actylcholine.
Baclofen mimics the effect of gamma-aminobutyric acid, an inhibitory neurotransmitter in both the peripheral and central nervous system. Baclofen reduces peripheral spasticity. A major side effect of baclofen is sedation. The ratio of sedation to spasticity reduction may be enhanced by intrathecal administration.
 
■Correct Answer:Baclofen mimics the effect of gamma-aminobutyric acid (GABA).
1940. (924) Q5-1195:
The migration index of Reimers is best described as:
1) The vertical migration of the center of the femoral head with respect to the lateral margin of the acetabulum.
3) The ratio of the uncovered portion of the femoral head to its total width.
2) The distance between the medial wall of the acetabulum and the femoral head.
5) The angle between two lines through the center of the femoral head â one vertical and one through the lateral edge of the acetabulum.
4) The difference in subluxation between neutral and abduction films.
The migration index of Reimers is used to quantitate hip subluxation in cerebral palsy. It is defined as the ratio of the uncovered portion of the femoral head (lateral to a vertical line through the outer edge of the acetabulum) to the total width of the head.
 
■Correct Answer:The ratio of the uncovered portion of the femoral head to its total width.
1941. (925) Q5-1196:
An appropriate indication for preoperative magnetic resonance imaging in adolescent idiopathic scoliosis is:
1) Any curve requiring surgery
3) An abnormal neurologic examination
2) Any curve more than 90°
5) Any progression of 12° in 6 months
4) Any progressive deformity in a male
The only absolute indication for preoperative magnetic resonance imaging in idiopathic adolescent scoliosis is an abnormal neurologic exam or abnormal curve pattern.
 
■Correct Answer:An abnormal neurologic examination
1942. (926) Q5-1197:
The mean C obb measurement for idiopathic scoliosis curves with a 7° angle of trunk rotation (ATR) is:
1) 10°
3) 20°
2) 15°
5) 30°
4) 25°
Although the angle of trunk rotation (ATR) does not convert directly to a C obb angle, there are population-based figures for mean curve at each ATR. The mean C obb angle for curves having a 7° ATR is 20°.
 
■Correct Answer:20°
1943. (927) Q5-1198:
Using a 5° angle trunk rotation (ATR) as a positive screening threshold for detection of curves with a C obb angle over 20° is characterized by:
1) A high degree of sensitivity and specificity
3) A high degree of specificity but low sensitivity
2) A high degree of sensitivity but low specificity
5) No predictable relationship to C obb angle
4) A low degree of sensitivity and specificity
Use of a 5° ATR threshold for detection of curves with a C obb angle over 20° has a sensitivity of 98%, but a specificity of only
64%.
 
■Correct Answer:A high degree of sensitivity but low specificity
1944. (928) Q5-1199:
The normal values (±2 standard deviations) for kyphosis in the general population of children and adolescents are:
1) 20° to 50°
3) 25° to 45°
2) 20° to 40°
5) 30° to 60°
4) 25° to 60°
The normal values for kyphosis in the general population (2 standard deviations above and below the mean) are 20° to 50°. 
■Correct Answer:20° to 50°
1945. (929) Q5-1200:
Which of the following is the most common cause of death in children with pelvic fractures:
1) Intrapelvic exsanguination
3) Pulmonary embolism
2) Head injury
5) Spinal cord injury
4) Multisystem organ failure
Head injury is the cause of virtually all mortality in children with pelvic fractures. The rarity of life-threatening intrapelvic hemorrhage is in marked contrast to adults. Pulmonary embolism and multisystem organ failure are rare in children.
 
■Correct Answer:Head injury
1946. (930) Q5-1201:
An 8-year-old pedestrian sustains a pelvic fracture when struck by a car. The injury consists of a posterior iliac fracture in which the iliac wing is rotated internally, although it is not vertically displaced. An anterior fracture of both ipsilateral pubic rami is present with 2 cm of overlap. Recommended treatment includes:
1) Open reduction and plate fixation of the rami
3) Percutaneous sacral screw fixation
2) Open reduction and plate fixation of the iliac wing
5) Bedrest
4) External fixation
A childâs pelvis can absorb a significant amount of energy without serious displacement. There is rapid healing and good remodeling potential. Bedrest is the appropriate treatment for this patient because of the low risk of complications.
 
■Correct Answer:Bedrest
1947. (931) Q5-1202:
Which of the following factors should prompt a workup for an underlying disorder in a patient with slipped capital femoral epiphysis:
1) A bilateral slip
3) Weight under the 50th percentile for age
2) Weight over the 50th percentile for age
5) A slip of grade II or higher
4) A positive family history
A positive age-weight test is defined as a patient who is under the 50th percentile of weight for age or older than 16 years of age at presentation with slipped capital femoral epiphysis. These patients should have a workup for underlying renal or endocrine disease. A positive family history is found in 5% to 10% of patients with slipped capital femoral epiphysis.
 
■Correct Answer:Weight under the 50th percentile for age
1948. (932) Q5-1203:
Which of the following categories of slipped capital femoral epiphysis (SC FE) is associated with the highest risk of a grade III
slip:
1) Idiopathic SC FE
3) Radiation therapy
2) Renal failure
5) Growth hormone deficiency
4) Hypothyroidism
A grade III slip refers to more than 50% displacement of the epiphysis. Renal failure is associated with the highest risk (43%) of progressing to a grade III slip. Fortunately, these slips are usually stable.
 
■Correct Answer:Renal failure
1949. (1089) Q5-1449:
Which of the following is the central element of Klippel-Feil syndrome:
1) A low posterior hairline
3) C ervical stenosis
2) Hearing impairment
5) C ervical scoliosis
4) C ongenital cervical fusion
The essential feature of the definition of Klippel-Feil syndrome is congenital cervical fusion. Features other than congenital cervical fusion are sometimes seen but are not essential features of the syndrome. Features other than those listed above include scoliosis in different regions of the spine, congenital heart defects, a short neck, Sprengel deformity, and renal anomalies.
 
■Correct Answer:C ongenital cervical fusion
1950. (1090) Q5-1450:
The most common cause of neurologic deficit in patients with Down syndrome is:
1) Basilar invagination
3) Atlantoaxial instability
2) Atlanto-occipital instability
5) C ervical kyphosis
4) Subaxial instability
Basilar invagination is extremely rare in this syndrome, and problematic cervical kyphosis is equally uncommon. Atlanto-occipital translation and subaxial instability occur but rarely cause symptoms. Atlantoaxial instability is the most common of the cervical abnormalities listed to cause neurologic compromise in Down syndrome. Nevertheless, surgery is only indicated if the atlantoaxial interval exceeds 6 mm, or causes neurologic deficits.
■Correct Answer:Atlantoaxial instability