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Question 1

A 12-year-old boy comes to your office 2 weeks after a distal radius physeal fracture, which has been splinted in the emergency department. The epiphysis is displaced dorsally by 50%, and the articular surface has a dorsal tilt of 17°. You recommend:

Explanation

Distal radial physeal fractures are common injuries. Reduction should be done gently and not repeated multiple times. Fractures presenting late like this one are difficult to manipulate atraumatically, but have good remodeling potential. Therefore, a cast should be applied to limit any further displacement, but no manipulation or operation is recommended.

Question 2

Which of the following lowers the chance of a good result from stretching of muscular torticollis in infants:

Explanation

Stretching produces good results in more than 90% of infants. Presence of a palpable mass in the sternomastoid predicts a lower success rate than absence of such a mass. The other factors are either positive or neutral.

Question 3

A 14-year-old boy suffers a hip dislocation in a motor vehicle accident. It is reduced by closed means. The risk of avascular necrosis is:

Explanation

Avascular necrosis is a risk of traumatic hip dislocation. The risk is closest to 10%.

Question 4

Which of the following statements is true of the King classification of idiopathic scoliosis:

Explanation

The Lenke system is more comprehensive than the King system, for the latter considers the entire range or thoracolumbar and lumbar curve possibilities, as well as the sagittal plane. The Lenke system also appears to have a higher interobserver reliability.

Question 5

The most common form of chondrodysplasia punctata is much more common in girls than in boys. Which of the following explains this:

Explanation

X-linked dominant inheritance would explain the preponderance of girls with this condition, because they have twice as great a chance of having an affected x-chromosome. One affected x-chromosome is sufficient to convey the disease in a dominant condition. The imprinting phenomenon refers to a condition that varies depending upon whether the mother or the father passed it on (as in Angelman versus Prader-Willi syndromes).

Question 6

A 9-year-old boy injures his elbow in a fall from a 12-foot height. Radiographs reveal a posterior dislocation of the elbow with a fracture of the medial epicondyle which is displaced. The ossification center is 5 mm in diameter. You recommend:

Explanation

A recent long-term study has shown that open reduction of displaced medial epicondyle fractures does not yield superior results to closed treatment. This applies even when the elbow is initially dislocated. Excision of the epicondyle with suture of the ligament yields the highest incidence of late problems, such as flexion contractures and degenerative changes.

Question 7

The most accurate and practical means of determining pregnancy status in adolescent females undergoing surgery is:

Explanation

Anesthesia and surgery can be detrimental to a fetus, especially during the first trimester. Patient self-report is not accurate in many cases. Immunospot testing of the first morning urine for human chorionic gonadotropin is 99.4% sensitive and specific, rapid, and inexpensive. Serum HC G testing is less rapid and more expensive; therefore, not appropriate for surgical screening. The other tests are not used to ascertain pregnancy status.

Question 8

Which of the following is considered a critical element in surgically correcting posttraumatic elbow flexion contractures in adolescents:

Explanation

Bae and Waters have shown that adolescents with significant posttraumatic elbow flexion contractures can gain an average of 54° of motion with surgical release. They believe postoperative physical therapy and continuous passive motion are considered critical to success of surgical release. Lengthening of the biceps or triceps is not recommended. Measures to prevent postoperative heterotopic ossification did not influence the outcome.

Question 9

Which of the following statements is true concerning atlanto-occipital dislocations in children:

Explanation

Pediatric atlanto-occipital dislocation is increasing in frequency due to improved emergency care. Although the injuries are sometimes fatal and are often accompanied by severe spinal cord injury, this is not always the case. Although the dens-basion distance should be less than 10 mm and the power ratio should be less than 1 in normals, these are not always abnormal in children with such injuries. Clinical and radiographic correlation, with computer tomography or magnetic resonance imaging if needed, are called for to maximize diagnosis.

Question 10

Equinovarus positioning of the foot is normal during which stage of embryonic life:

Explanation

As the foot matures, it passes through a normal stage when it resembles a clubfoot in the eighth to tenth week. After this, the foot normally corrects itself.

Question 11

Which of the following is a similarity between congenital pseudarthrosis of the clavicle and congenital pseudarthrosis of the tibia:

Explanation

Congenital pseudarthrosis of the clavicle and tibia may present in infants with a gap between two tapered, atrophic bone ends. However, they are dissimilar in other respects. Pseudarthrosis of the clavicle is seen almost exclusively on the right side, while that of the tibia is seen on either side. Pseudarthrosis of the clavicle may be seen in cleidocranial dysostosis, although tibial pseudarthrosis is not. Pseudarthrosis of the clavicle has a high rate of union with simple bone graft, while that of the tibia does not. One-half of patients with pseudarthrosis of the tibia have neurofibromatosis, while this is almost never seen in congenital pseudarthrosis of the clavicle.

Question 12

A 13-year-old boy has a left slipped capital femoral epiphysis which has displaced 75%. He is unable to bear weight on the limb. The other hip has no clinical or radiographic abnormalities. Your preferred treatment is which of the following:

Explanation

This is an unstable slip. It has a much higher chance of avascular necrosis than a stable slip. Since the degree of the slip will increase the shear forces across the healing physis and decrease the function of the hip, some method of improving this is justified. Gentle reduction of the epiphysis, without forceful internal rotation, may increase the risk of avascular necrosis. Avascular necrosis is a significant risk in many series of cuneiform (metaphyseal; Fish) osteotomies. Subtrochanteric osteotomy is not justified in patients with an acute slip until it is healed. It has a high rate of chondrolysis. Free vascularized bone graft may be an option if avascular necrosis develops, but is not indicated at this time. A hip spica cast is also often followed by chondrolysis and delayed epiphyseodesis.

Question 13

Of all slipped capital femoral epiphyses, which percentage is unstable:

Explanation

Unstable slipped capital femoral epiphysis places the patient at a high risk of avascular necrosis (up to 47%). Fortunately, it comprises only about 5% of all slips.

Question 14

The normal value for the hallux valgus angle is:

Explanation

The angle between the first metatarsal and its proximal phalanx is normally one of mild (10° to 20°) valgus. It is not normal for it to be too straight. An increase in this angle beyond this value is often noted by the patient as a bunion.

Question 15

A 13-year-old girl is seen in clinic for bunion. She is asymptomatic but has a hallux valgus angle of 29°, an intermetatarsal angle of 15°, and a medial prominence over the first metatarsal head. The family asks whether anything can be done to prevent future problems with the foot. You recommend:

Explanation

Bunions may often be treated conservatively, and it is impossible to predict which ones will later develop symptoms. Surgical reconstruction of bunions in adolescents has a higher rate of recurrence than in adults in many reported series. For all of these reasons, nonoperative treatment is preferred for asymptomatic patients.

Question 16

Which of the following tendons is not usually contracted in a patient with untreated vertical talus:

Explanation

A vertical talus is a fixed dorsolateral dislocation of the talonavicular joint. The forefoot is in calcaneus and the hindfoot is in equinus. Therefore, all of the tendons listed except for the posterior tibialis are contracted.

Question 17

A 9-year-old boy is seen because of pain medially, in the arch of the foot. His ankle dorsiflexion is limited to 10Â° with the knee extended. Radiograph shows an accessory navicular, which corresponds to the point of his tenderness. You recommend:

Explanation

Accessory navicular is seen in 10% to 14% of normal children. Sometimes, it becomes symptomatic in juveniles or adolescents, but this usually resolves by skeletal maturity. Conservative treatment, such as activity restriction, arch support, and stretching the Achilles if tight, will usually alleviate symptoms.

Question 18

Which of the following disorders is due to a defect in anterior horn cells:

Explanation

Charcot-Marie-Tooth disease is due to a defect in peripheral nerves; Duchenne muscular dystrophy is due to a defect in dystrophin, affecting the muscle cell membrane; Friedreich ataxia is a degeneration of the spinocerebellar tracts. Rett syndrome is due to a defect in MEC P-2 protein, affecting the brain. Only spinal muscular atrophy is due to a defect in anterior horn cells.

Question 19

Becker muscular dystrophy is due to a defect in the gene for which of the following:

Explanation

Becker muscular dystrophy has a defect in the same gene as Duchenne muscular dystrophy, namely the protein dystrophin. The mutation in Becker dystrophy results in a truncated protein that retains some function, whereas the mutation in Duchenne dystrophy is different and results in an unstable protein, which is degraded quickly.

Question 20

Which of the following muscles is first affected in facioscapulohumeral dystrophy:

Explanation

In facioscapulohumeral dystrophy, the facial muscles are affected first, commonly presenting with an inability to whistle. The serratus muscles and scapular stabilizers are affected next. The deltoid, supraspinatus, and infraspinatus are typically not affected in this disease.

Question 21

Emery-Dreifuss muscular dystrophy is unique among the dystrophies because of the development of which deformity:

Explanation

Emery-Dreifuss muscular dystrophy is an x-linked disorder of emerin, which is a cell-membrane protein. Symptoms and signs develop within the first decade in most cases. A unique deformity, neck extension contracture, develops, in addition to elbow flexion contractures and peroneal wasting. The other deformities listed above are common in many dystrophies.

Question 22

Electrodiagnostic testing in myopathies typically shows all of the following except:

Explanation

Electrodiagnostic testing in myopathy typically shows low amplitude, polyphasic EMG potentials with a decreased duration of response. Nerve conduction velocity is normal, in contrast to findings in neuropathies. Fibrillations are not typically seen; these are more characteristic of neuropathy.

Question 23

In which region is direct anatomical extension from the metaphysis of a long bone to the adjacent joint not anatomically possible in the child:

Explanation

The metaphysis of the proximal humerus lies partially within the shoulder joint; similarly, that of the proximal radius lies within the elbow. The metaphysis of the proximal femur lies within the hip joint and that of the distal lateral tibia within the ankle joint. There is no intra-articular metaphysis about the knee, however.

Question 24

Which of the following skeletal dysplasias is not commonly associated with non-orthopedic complications:

Explanation

McKusick dysplasia is commonly associated with immune and gastrointestinal disorders. Hurler syndrome is associated with progressive mental retardation, hepatosplenomegaly, and cataracts. Morquio syndrome is associated with cardiorespiratory difficulties. C hondroectodermal dysplasia, or Ellis van C reveld syndrome, is associated with congenital heart disease. Multiple epiphyseal dysplasia, however, is not associated with systemic non- orthopaedic complications.

Question 25

Which of the following by itself is not an indication for surgery in a child with acute hematogenous osteomyelitis:

Explanation

Surgery is indicated in situations in which antibiotics alone will not be curative, including subperiosteal abscess, sequestrum, intramedullary abscess, and adjacent septic arthritis. Fever alone is not an indication for surgery.

Question 26

Which of the following is not usually seen in chronic recurrent multifocal osteomyelitis:

Explanation

Chronic recurrent multifocal osteomyelitis is believed to be an idiopathic noninfectious inflammatory disease. It has gradual onset of symptoms, and sites most commonly involved are the spine, long bones, and feet. Nonsteroidal anti-inflammatory drugs typically improve symptoms. Cultures are negative.

Question 27

A 5-year-old child is bitten by a tick. Which of the following has been shown to aid in management:

Explanation

Prompt tick removal is recommended because Lyme disease is more likely if the tick is attached for more than 24 hours. Immediate antibiotic administration is not recommended because the incidence of Lyme disease is low after any single tick bite and treatment is equally effective once the disease is diagnosed. Doxycycline is not recommended in children younger than 8 years old because of dental discoloration. Immediate testing for antibodies (ELISA) is not useful because antibodies do not rise for at least several weeks. Steroids are not recommended in this setting.

Question 28

Which of the following measures has not been shown to decrease rates of injury in healthy children participating in recreational sports:

Explanation

Knee braces have been shown not to reduce injury rates for children for children with sound knees. All other measures have been shown to reduce injury rates.

Question 29

Which recreational activity causes the most musculoskeletal injuries in children ages 5 to 14 in the United States:

Explanation

Bicycles are the leading cause of musculoskeletal injury in American children, with 415,000 injuries per year, followed by basketball, football, and roller sports.

Question 30

The effects of pediatric orthopedic conditions in later adulthood commonly determine treatment choices for children. At what threshold does limb length discrepancy increase the energy cost of walking in older adults:

Explanation

A limb length discrepancy of as little as 2 cm has shown to increase perceived exertion as well as oxygen consumption in older adults.

Question 31

Anterior elbow release in children with cerebral palsy is likely to result in which of the following outcomes:

Explanation

Anterior elbow release consists of lengthening of the lacertus fibrosus and the brachialis fascia. It may or may not include lengthening of the biceps tendon itself. Anterior elbow release effectively decreases the excessive flexion posture of the elbow during use, which one author has termed the â flexion posture angle.â It does not result in decreased (or increased) strength of elbow flexion if the biceps tendon is preserved. Unfortunately, increased use during bimanual activity and increased grip strength are usually not observed.

Question 32

Which of the following procedures is most likely to correct idiopathic toe walking with a single treatment:

Explanation

Percutaneous tendoachilles lengthening is most likely to resolve idiopathic toe walking in a single treatment. The other methods have a higher likelihood of persistent toe walking.

Question 33

Core binding factor alpha 1 (C bfa1) is a transcription factor having which of the following effects:

Explanation

Cbfa1 is a transcription factor that causes cells to differentiate into osteoblasts. An abnormality in its gene causes cleidocranial dysplasia.

Question 34

Which of the following is found less often in children with lumbosacral agenesis as compared to controls:

Explanation

Patients with lumbosacral agenesis often have knee flexion contractures as compared with controls. All of the other features listed are common in patients with lumbosacral agenesis.

Question 35

Which of the following figures most closely approximates the prevalence of defects in the L5 pars interarticularis in a newborn:

Explanation

Pars interarticularis defects are not found in newborns, whereas the incidence is 5% in patients who are in the first grade. It remains close to this figure throughout later life.

Question 36

Which of the following is the most common cause of low back pain in young athletes:

Explanation

Spondylolysis is the most common cause of back pain in young athletes, accounting for approximately 50% of cases. The other causes are significantly less common.

Question 37

A 7-year-old boy with cerebral palsy, total involvement type, has neuromuscular hip dysplasia. The migration index is 60% without flattening. He has had pain in the groin for the past 6 months. Recommended treatment includes:

Explanation

Pain in the spastic patient with subluxation without head deformity is most appropriately treated by reduction. Adductor tenotomy alone is not recommended when the hip subluxation exceeds 50% or the age is greater than 5 to 6 years. Femoral osteotomy should be added. Salvage procedures such as proximal femoral resection, arthrodesis, or arthroplasty are not indicated.

Full Question & Answer Text (for Search Engines)

Question 1:

Options:

C losed manipulation with sedation
C losed manipulation under anesthesia with relaxation
Open reduction, internal fixation
C ast application and observation
Percutaneous pin fixation in current position

Correct Answer: C ast application and observation

Explanation:

Question 2:

Which of the following lowers the chance of a good result from stretching of muscular torticollis in infants:

Options:

Palpable mass in the sternocleidomastoid muscle
Age at presentation less than 1 month
Rotation to neutral
Absence of plagiocephaly
High birth weight

Correct Answer: Palpable mass in the sternocleidomastoid muscle

Explanation:

Question 3:

A 14-year-old boy suffers a hip dislocation in a motor vehicle accident. It is reduced by closed means. The risk of avascular necrosis is:

Options:

Less than 5%
10%
20%
40%
50%

Correct Answer: 10%

Explanation:

Avascular necrosis is a risk of traumatic hip dislocation. The risk is closest to 10%.

Question 4:

Which of the following statements is true of the King classification of idiopathic scoliosis:

Options:

It takes into account sagittal alignment of curves.
It defines structural and nonstructural curves.
It classifies all possible curve patterns.
It has a lower interobserver reliability than the Lenke system.
It has more curve types than the Lenke system.

Correct Answer: It has a lower interobserver reliability than the Lenke system.

Explanation:

Question 5:

The most common form of chondrodysplasia punctata is much more common in girls than in boys. Which of the following explains this:

Options:

Autosomal dominant inheritance
X-linked dominant inheritance
X-linked recessive inheritance
Autosomal recessive inheritance
The imprinting phenomenon

Correct Answer: X-linked dominant inheritance

Explanation:

Question 6:

Options:

Open reduction internal fixation with a smooth pin
Open reduction internal fixation with a small screw
Open reduction and fixation with a suture
Open reduction with excision of the fragment and suture of the medial collateral ligament
C losed reduction of the dislocation and application of a splint

Correct Answer: C losed reduction of the dislocation and application of a splint

Explanation:

Question 7:

The most accurate and practical means of determining pregnancy status in adolescent females undergoing surgery is:

Options:

Self report
Morning urine human chorionic gonadotropin (HC G)
Serum HC G
Serum alpha fetoprotein
Serum estrogen levels

Correct Answer: Morning urine human chorionic gonadotropin (HC G)

Explanation:

Question 8:

Which of the following is considered a critical element in surgically correcting posttraumatic elbow flexion contractures in adolescents:

Options:

Lengthening of the biceps muscle
Lengthening of the triceps muscle
Perioperative indomethacin
Pre- or postoperative radiation
Postoperative continuous passive motion and physical therapy

Correct Answer: Postoperative continuous passive motion and physical therapy

Explanation:

Question 9:

Which of the following statements is true concerning atlanto-occipital dislocations in children:

Options:

The dens-basion distance is greater than 10 mm.
The power ratio is greater than 1.0.
The injury is not survivable.
Spinal cord injury always accompanies this dislocation.
No single plain radiographic finding is always diagnostic.

Correct Answer: No single plain radiographic finding is always diagnostic.

Explanation:

Question 10:

Equinovarus positioning of the foot is normal during which stage of embryonic life:

Options:

No stage
Eighth to tenth week
Thirteenth to fifteenth week
Seventeenth to nineteenth week
Twentieth to twenty-third week

Correct Answer: Eighth to tenth week

Explanation:

As the foot matures, it passes through a normal stage when it resembles a clubfoot in the eighth to tenth week. After this, the foot normally corrects itself.

Question 11:

Which of the following is a similarity between congenital pseudarthrosis of the clavicle and congenital pseudarthrosis of the tibia:

Options:

Both are common in neurofibromatosis
Both are common in cleidocranial dysplasia
Both have a low rate of union after treatment with autograft unless it is vascularized
Both are more common on the left side
Both may present with tapered, atrophic bone ends at the pseudarthrosis

Correct Answer: Both may present with tapered, atrophic bone ends at the pseudarthrosis

Explanation:

Question 12:

Options:

Gentle reduction of the slip and fixation with a cannulated screw
Hip spica cast
C uneiform osteotomy
Subtrochanteric osteotomy
Free vascularized fibular grafting

Correct Answer: Gentle reduction of the slip and fixation with a cannulated screw

Explanation:

Question 13:

Of all slipped capital femoral epiphyses, which percentage is unstable:

Options:

Correct Answer: 5%

Explanation:

Unstable slipped capital femoral epiphysis places the patient at a high risk of avascular necrosis (up to 47%). Fortunately, it comprises only about 5% of all slips.

Question 14:

The normal value for the hallux valgus angle is:

Options:

0° to 5°
10° to 20°
5° to 10°
30° to 40°
20° to 30°

Correct Answer: 10° to 20°

Explanation:

Question 15:

Options:

Osteotomy of the first metatarsal base
Hemiepiphyseodesis of the medial physis of the first metatarsal
Double osteotomy of the first metatarsal
Mitchell osteotomy
Shoe modifications if symptoms develop

Correct Answer: Shoe modifications if symptoms develop

Explanation:

Question 16:

Which of the following tendons is not usually contracted in a patient with untreated vertical talus:

Options:

Anterior tibialis
Posterior tibialis
Peroneus brevis
Extensor digitorum longus
Achilles

Correct Answer: Posterior tibialis

Explanation:

Question 17:

Options:

Excision of the accessory navicular
Excision of the accessory navicular with advancement of the posterior tibialis tendon
Evans procedure (lateral column lengthening)
Tendoachilles lengthening
Activity restriction, stretching, arch support

Correct Answer: Activity restriction, stretching, arch support

Explanation:

Question 18:

Which of the following disorders is due to a defect in anterior horn cells:

Options:

Charcot-Marie-Tooth
Duchenne dystrophy
Friedreichâ s ataxia
Spinal muscular atrophy
Rett syndrome

Correct Answer: Spinal muscular atrophy

Explanation:

Question 19:

Becker muscular dystrophy is due to a defect in the gene for which of the following:

Options:

Dystrophin
Sarcoglycan
Myelin
Sulfate transport
Fibroblast growth factor receptor

Correct Answer: Dystrophin

Explanation:

Question 20:

Which of the following muscles is first affected in facioscapulohumeral dystrophy:

Options:

Orbicularis oris
Serratus anterior
Deltoid
Supraspinatus
Infraspinatus

Correct Answer: Orbicularis oris

Explanation:

Question 21:

Emery-Dreifuss muscular dystrophy is unique among the dystrophies because of the development of which deformity:

Options:

Neck extension contracture
Hip abduction
Knee flexion
Equinus contracture
Scoliosis

Correct Answer: Neck extension contracture

Explanation:

Question 22:

Electrodiagnostic testing in myopathies typically shows all of the following except:

Options:

Low amplitude electromyogram (EMG) potentials
Polyphasic EMG potentials
Normal nerve conduction velocity
Decreased duration of EMG response
Fibrillation potentials

Correct Answer: Fibrillation potentials

Explanation:

Question 23:

In which region is direct anatomical extension from the metaphysis of a long bone to the adjacent joint not anatomically possible in the child:

Options:

Shoulder
Elbow
Hip
Knee
Ankle

Correct Answer: Knee

Explanation:

Question 24:

Which of the following skeletal dysplasias is not commonly associated with non-orthopedic complications:

Options:

McKusick metaphyseal chondrodysplasia
Hurler syndrome
Morquio syndrome
C hondroectodermal dysplasia
Multiple epiphyseal dysplasia

Correct Answer: Multiple epiphyseal dysplasia

Explanation:

Question 25:

Which of the following by itself is not an indication for surgery in a child with acute hematogenous osteomyelitis:

Options:

Fever higher than 38.5°
Subperiosteal abscess
Presence of a sequestrum
Intramedullary abscess
Adjacent septic arthritis

Correct Answer: Fever higher than 38.5°

Explanation:

Question 26:

Which of the following is not usually seen in chronic recurrent multifocal osteomyelitis:

Options:

Positive cultures for Staphylococcus epidermidis
Gradual onset of symptoms
Involvement of the spine, long bones, and feet
Negative cultures
Improvement with nonsteroidal anti-inflammatory agents

Correct Answer: Positive cultures for Staphylococcus epidermidis

Explanation:

Question 27:

A 5-year-old child is bitten by a tick. Which of the following has been shown to aid in management:

Options:

Prompt tick removal
Immediate treatment with doxycycline
Immediate treatment with amoxicillin
Prompt ELISA testing
Steroid administration

Correct Answer: Prompt tick removal

Explanation:

Question 28:

Which of the following measures has not been shown to decrease rates of injury in healthy children participating in recreational sports:

Options:

Knee braces during basketball and football
Ankle braces in basketball
Helmets for bicyclists
Mouth guards for basketball
Break-away bases for baseball

Correct Answer: Knee braces during basketball and football

Explanation:

Knee braces have been shown not to reduce injury rates for children for children with sound knees. All other measures have been shown to reduce injury rates.

Question 29:

Which recreational activity causes the most musculoskeletal injuries in children ages 5 to 14 in the United States:

Options:

Bicycles
Football
Soccer
Trampolines
Gymnastics

Correct Answer: Bicycles

Explanation:

Bicycles are the leading cause of musculoskeletal injury in American children, with 415,000 injuries per year, followed by basketball, football, and roller sports.

Question 30:

Options:

2 cm
3 cm
4 cm
5 cm
No such effect has been proven at any discrepancy.

Correct Answer: 2 cm

Explanation:

A limb length discrepancy of as little as 2 cm has shown to increase perceived exertion as well as oxygen consumption in older adults.

Question 31:

Anterior elbow release in children with cerebral palsy is likely to result in which of the following outcomes:

Options:

Decreased flexion posture during use
Decreased flexion contracture
Increased use during bimanual activity
Increased strength of elbow flexion
Increased grip strength

Correct Answer: Decreased flexion posture during use

Explanation:

Question 32:

Which of the following procedures is most likely to correct idiopathic toe walking with a single treatment:

Options:

Stretching program
Ankle foot orthosis
Stretching cast
Botulinum toxin injection
Percutaneous tendoachilles lengthening

Correct Answer: Percutaneous tendoachilles lengthening

Explanation:

Percutaneous tendoachilles lengthening is most likely to resolve idiopathic toe walking in a single treatment. The other methods have a higher likelihood of persistent toe walking.

Question 33:

Core binding factor alpha 1 (C bfa1) is a transcription factor having which of the following effects:

Options:

Cbfa1 induces cells to differentiate into osteoblasts.
Cbfa1 induces cells to differentiate into osteoclasts.
Cbfa1 inhibits endochondral ossification.
Cbfa1 impairs sulfation of proteoglycans.
Cbfa1 causes premature cell death.

Correct Answer: Cbfa1 induces cells to differentiate into osteoblasts.

Explanation:

Cbfa1 is a transcription factor that causes cells to differentiate into osteoblasts. An abnormality in its gene causes cleidocranial dysplasia.

Question 34:

Which of the following is found less often in children with lumbosacral agenesis as compared to controls:

Options:

C ervical spine anomalies
Maternal diabetes
Hip dislocation
Spina bifida
Genu recurvatum

Correct Answer: Genu recurvatum

Explanation:

Patients with lumbosacral agenesis often have knee flexion contractures as compared with controls. All of the other features listed are common in patients with lumbosacral agenesis.

Question 35:

Which of the following figures most closely approximates the prevalence of defects in the L5 pars interarticularis in a newborn:

Options:

Less than 1%
3%
5%
10%
15%

Correct Answer: Less than 1%

Explanation:

Pars interarticularis defects are not found in newborns, whereas the incidence is 5% in patients who are in the first grade. It remains close to this figure throughout later life.

Question 36:

Which of the following is the most common cause of low back pain in young athletes:

Options:

Thoracolumbar Scheuermann apophysitis
Herniated nucleus pulposus
Slipped vertebral apophysis
Spondylolysis
Avulsion of the spinous apophysis

Correct Answer: Spondylolysis

Explanation:

Spondylolysis is the most common cause of back pain in young athletes, accounting for approximately 50% of cases. The other causes are significantly less common.

Question 37:

Options:

Adductor tenotomy
Adductor tenotomy and femoral osteotomy
Proximal femoral resection
Hip arthrodesis
Total hip arthroplasty

Correct Answer: Adductor tenotomy

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