Creator: Dr. Mohammed hutaif
Published: 2026-04-25T20:18:29.953765+00:00

Orthopedic Prometric MCQs - Chapter 3 Part 1

Comprehensive 100-Question Exam

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Question 1

The Ponseti method of clubfoot cast treatment starts with which of the following steps:

Explanation

Dorsiflexion of the first ray is the first step in the Ponseti method of cast treatment. Dorsiflexion decreases the cavus component. Pronation of the forefoot is the opposite of dorsiflexion and produces the opposite desired motion. Dorsiflexion of the ankle should be performed after the Achilles tenotomy. External rotation of the foot is performed later. Internal rotation of the clubfoot is never done.

Question 2

When correcting a clubfoot by the Ponseti method, the lateral mold on the foot must be placed against which of the following structures:

Explanation

Ponseti describes rotating the clubfoot against the head of the talus to allow the lateral side of the foot (calcaneus and cuboid) to rotate laterally.

Question 3

Which of the following molecules is defective in osteogenesis imperfecta:

Explanation

Osteogenesis imperfecta (OI) is a disorder of type I collagen. Numerous different mutations in the genes for this molecule have been described, accounting for the variable clinical phenotypes. Type II collagen is important for articular cartilage, but it is not implicated in the pathogenesis of OI. The other factors are not abnormal in OI.

Question 4

Regulation of proximal-to-distal development of the limbs is determined by which of the following:

Explanation

Proximal-to-distal development of the limbs in utero is determined by the homeobox genes. These genes are located on a number of different chromosomes (2, 7, 12, and 17), and they guide the proximal-to-distal organization of limb and digital development.

Question 5

Meryon sign refers to which of the following physical phenomena in patients with muscular dystrophies:

Explanation

Meryon sign is the weakness of shoulder adduction when a child is lifted or suspended under the axillae. The examiner will feel that the child is slipping through his or her hands. It is due to weakness of the shoulder girdle muscles. Meryon sign is present in limb-girdle dystrophies and fascioscapulohumeral dystrophy.

Question 6

Spinal muscular atrophy is best characterized as which of the following:

Explanation

Spinal muscular atrophy is a degeneration of the anterior horn cells of the spinal cord. It results in a nonprogressive lower motor neuron disease with preservation of sensation and intelligence. There is no spasticity or hyperreflexia.

Question 7

Which of the following is the gene that is abnormal in spinal muscular atrophy:

Explanation

Spinal muscular atrophy is a disorder of survival motor neuron genes 1 and 2; its product is not yet known. Dystrophin is abnormal in Duchenne and Becker muscular dystrophy. Frataxin is abnormal in Friedreich ataxia. Peripheral myelin protein is defective in C harcot-Marie-Tooth disease. Emerin is abnormal in Emery-Dreifuss syndrome.

Question 8

Emery-Dreifuss syndrome is manifest by all of the following except:

Explanation

Emery-Dreifuss syndrome is due to an encoding error in emerin, which may be a stabilizer of the nuclear membrane. Emery- Dreifuss syndrome is characterized by a triad of contractures of the heel cord, elbow, and cervical spine. Cardiomyopathy may cause heart block or other arrhytmias. Scoliosis is not commonly found in this condition.

Question 9

Which of the following bones of the foot is normally ossified at birth:

Explanation

The metatarsals are ossified at birth, along with the talus and the calcaneus. The cuboid ossifies at 1 month, followed by the third, second, and first cuneiforms. The navicular does not ossify until age 2 or 3 years. These facts are useful when interpreting radiographs for congenital foot deformities such as clubfoot. The location of the navicular must often be inferred from the position of the first metatarsal.

Question 10

C hronic recurrent multifocal osteomyelitis is caused by which of the following:

Explanation

Chronic recurrent multifocal osteomyelitis presents as chronic joint pain at multiple locations and at different times. No organism has been isolated from patients presenting with chronic recurrent multifocal osteomyelitis. There is no role for surgery or antibiotics because symptoms generally resolve over a period of time.

Question 11

A 5-year-old boy has midfoot pain and limps at the end of long walks. Radiographs show sclerosis and fragmentation of the navicular on the involved side. Recommended treatment is:

Explanation

Kohler s disease, or avascular necrosis of the tarsal navicular, occurs spontaneously. It is more common in boys than girls, and it frequently presents before the age of 8 years. C onservative treatment consisting of counseling and activity modification is usually sufficient, with reossification ensuing. Occasionally cast immobilization seems helpful in allaying symptoms.

Question 12

An 11-year-old girl presents with pain in the area of the second metatarsophalangeal joint. Pain is increased with joint motion. Radiographs show increased density and flattening of the metatarsal head. Recommended treatment is:

Explanation

Freibergs disorder, or osteochondrosis of the second metatarsal head, is most common in teenage girls, especially dancers. The length of this metatarsal may be a factor in the pathogenesis. Treatment must be conservative in most cases, although a mild degree of symptoms may persist if epiphyseal flattening does not remodel.

Question 13

Which of the following complications is not a recognized risk of the Salter osteotomy:

Explanation

Avascular necrosis is not a risk of the osteotomy, but rather of an open or closed reduction that may sometimes accompany it. All of the other complications are accepted as possible, although rare, sequelae of the procedure.

Question 14

The result of treatment of developmental dysplasia of the hip with Salter osteotomy is is worse with which of the following:

Explanation

Salter osteotomy is effective in treating developmental dysplasia of the hip in young children. The result is worse with higher degrees of dislocation as assessed by the Tonnis system. It is better if the open reduction (if needed) is performed as a separate step than the osteotomy. The other factors have not been shown to be predictive.

Question 15

A 4-year-old girl with developmental hip dysplasia is advised to have a Salter innominate osteotomy. When the family asks about the long-term survivorship of the reconstruction, the surgeon tells them that good 30-year follow-up results are likely in at least what percentage of patients:

Explanation

Thirty-year survivorship analysis shows good to excellent results in at least 85% of patients.

Question 16

Which of the following statements best describes the effect of leptin on the skeleton:

Explanation

Leptin is a polypeptide secreted by adipocytes and acts upon the hypothalamus as a powerful inhibitor of bone mass.

Question 17

Which of the following organisms is the most common cause of obturator internus muscle abscess in children:

Explanation

Abscess of the obturator internus muscle may mimic septic arthritis. It is best diagnosed by magnetic resonance image. <1>Staphylococcus aureus is the most common causative organism, accounting for 75% of cases of obturator internus muscle abscess. Antibiotic treatment should be tried first and is successful in most cases.

Question 18

Which of the following studies is likely to help in distinguishing osteomyelitis from infarct in a patient with sickle cell anemia:

Explanation

The combination of bone and bone marrow scan is the only imaging method that is useful in distinguishing osteomyelitis from infarct in patients with sickle cell anemia. The bone marrow scan is normal, but the bone scan shows increased uptake in a patient with osteomyelitis.

Question 19

A 10-year-old boy with diplegic cerebral palsy walks with his knees turned in significantly. He has the appearance of severe valgus when walking. When examined in a supine position, there is no excessive valgus of the knees. His popliteal angle is 45°. An Ely test is negative. His hip internal rotation in the prone position is 80°, while his external rotation is 15°. The surgeon wishes to improve the patientâ s knee position during gait. The intervention most likely to accomplish this is:

Explanation

The findings highlighted here are those of severe anteversion. Anteversion causes the appearance of valgus of the knees, and it does not resolve spontaneously in cerebral palsy. The procedure most likely to make a lasting improvement in the patient is derotational osteotomy of the femur.

Question 20

Which of the following procedures is most likely to increase recurvatum of the knee in patients with diplegic cerebral palsy:

Explanation

Lengthening of the medial and lateral hamstrings is more likely to overlengthen the posterior knee checkrein. Therefore, it should only be performed in selected cases with severe spasticity and no cospasticity of the rectus femoris. Lengthening of only the medial hamstrings carries less risk. The other procedures listed do not carry this risk.

Question 21

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip. The parents report that the infant has stopped kicking the affected leg over the past two days. On examination, there is decreased active knee extension but normal foot and toe movement. Which of the following is the most appropriate next step in management?

Explanation

The clinical presentation is highly suggestive of a femoral nerve palsy, a known complication of hyperflexion in a Pavlik harness. The most appropriate immediate management is to discontinue the harness or significantly loosen the anterior straps to allow the nerve to recover.

Question 22

Which of the following conditions constitutes the strongest absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a 12-year-old patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

Explanation

Endocrine and metabolic disorders, particularly renal osteodystrophy and hypothyroidism, significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these patients to prevent a subsequent slip.

Question 23

A 6-year-old boy presents with a completely displaced, extension-type supracondylar fracture of the humerus. Which of the following neurologic deficits is most commonly associated with this specific injury pattern?

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. AIN palsy presents with an inability to flex the IP joint of the thumb and the distal IP joint of the index finger, resulting in an abnormal "OK" sign.

Question 24

A 5-year-old child sustains a minimally displaced fracture of the lateral humeral condyle. The fracture is managed non-operatively in a cast but progresses to a delayed nonunion. If left untreated, this nonunion is most likely to result in which of the following long-term complications?

Explanation

Nonunion of a lateral condyle fracture typically leads to progressive cubitus valgus deformity. Over time, the valgus angulation stretches the ulnar nerve, commonly resulting in a tardy ulnar nerve palsy.

Question 25

According to the Gross Motor Function Classification System (GMFCS), a 6-year-old child with cerebral palsy classified as GMFCS level V requires which of the following hip surveillance protocols?

Explanation

Children with GMFCS level V cerebral palsy have the highest risk (up to 90%) of hip displacement. Surveillance guidelines recommend an AP pelvis radiograph every 6 months for these severely affected patients until skeletal maturity or stability is established.

Question 26

In a patient presenting with Legg-Calve-Perthes disease, which of the following combinations of factors at the time of presentation portends the poorest prognosis?

Explanation

The most significant prognostic factors in Legg-Calve-Perthes disease are the chronological age at onset and the extent of lateral pillar involvement (Herring classification). Onset after age 8 combined with greater than 50% lateral pillar collapse (Herring Group C) has the worst radiographic and clinical outcomes.

Question 27

A 2-year-old child is diagnosed with congenital scoliosis secondary to a fully segmented hemivertebra at T8. Which of the following routine screening evaluations is mandatory in the initial workup of this patient?

Explanation

Congenital scoliosis is frequently associated with VACTERL anomalies, with genitourinary abnormalities (such as unilateral renal agenesis) occurring in 20-30% of patients. A renal ultrasound and echocardiogram are mandatory components of the initial evaluation.

Question 28

A 1-year-old child with achondroplasia presents with hypotonia, apneas, and delayed motor milestones. Which of the following pathologic mechanisms is the most likely cause of these symptoms and represents the leading cause of mortality in this age group?

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis due to abnormal endochondral ossification of the skull base. This can cause cervicomedullary compression, leading to central sleep apnea, hypotonia, and sudden infant death if not decompressed surgically.

Question 29

A 13-year-old girl sustains a juvenile Tillaux fracture. Which of the following best describes the anatomical basis and mechanism of this specific fracture pattern?

Explanation

A juvenile Tillaux fracture occurs due to external rotation of the foot, where the anterior inferior tibiofibular ligament (AITFL) avulses the anterolateral aspect of the distal tibial epiphysis. This pattern occurs because the medial and central aspects of the distal tibial physis close before the lateral aspect.

Question 30

A 5-year-old boy presents with acute atraumatic right hip pain and a limp. He refuses to bear weight. His temperature is 38.8 C (101.8 F), ESR is 45 mm/hr, and WBC count is 13,500/mm3. According to the Kocher criteria, what is the approximate probability that this patient has septic arthritis rather than transient synovitis?

Explanation

The Kocher criteria include non-weight-bearing status, temperature >38.5 C, ESR >40 mm/hr, and WBC >12,000/mm3. The presence of all four criteria indicates an approximate 99% probability of septic arthritis.

Question 31

A 4-year-old boy, initially treated successfully for idiopathic clubfoot using the Ponseti method, presents with a relapse. He demonstrates dynamic supination of the foot during the swing phase of gait but passive range of motion is fully correctable. Which of the following is the most appropriate definitive management?

Explanation

Dynamic supination during the swing phase in a relapsed, previously corrected Ponseti clubfoot is caused by an overactive tibialis anterior tendon. The definitive treatment for a flexible foot in a child over age 2.5 is a whole tibialis anterior tendon transfer (TATT) to the lateral cuneiform.

Question 32

A 4-month-old infant is diagnosed with developmental dysplasia of the hip (DDH). Ultrasound confirms a dislocated hip. Which of the following is an absolute contraindication to the use of a Pavlik harness?

Explanation

Teratologic hip dislocations, often associated with arthrogryposis or myelomeningocele, are rigid and do not respond to Pavlik harness treatment. Closed or open reduction is typically required.

Question 33

An 11-year-old boy with a BMI in the 99th percentile presents with a unilateral stable slipped capital femoral epiphysis (SCFE). Prophylactic pinning of the contralateral asymptomatic hip is most strongly indicated in patients with which of the following concomitant conditions?

Explanation

Endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) significantly increase the risk of bilateral SCFE. This justifies prophylactic fixation of the contralateral hip.

Question 34

Which of the following factors at the time of presentation confers the worst prognosis in a child with Legg-Calve-Perthes disease?

Explanation

The Herring lateral pillar classification is highly prognostic. Lateral pillar type C (greater than 50% loss of lateral pillar height) predicts a poor radiographic and clinical outcome.

Question 35

A 5-year-old boy presents with right hip pain and a limp. According to the Kocher criteria, which set of findings yields the highest probability of septic arthritis?

Explanation

The Kocher criteria for septic arthritis of the hip include non-weight-bearing, ESR > 40 mm/hr, fever > 38.5 C, and WBC > 12,000/mm3. Having all four criteria gives a 99% probability of septic arthritis.

Question 36

A 6-year-old child with spastic quadriplegic cerebral palsy (GMFCS level V) is undergoing routine orthopedic surveillance. What is the most critical radiographic parameter to monitor for hip stability?

Explanation

Reimer's migration percentage is the standard measurement used in cerebral palsy hip surveillance. A migration percentage greater than 30% indicates subluxation and often warrants surgical intervention.

Question 37

A neonate is diagnosed with achondroplasia. The parents ask about potential severe neurological complications. Which of the following is the most life-threatening neurological complication in infants with this condition?

Explanation

Foramen magnum stenosis is a critical complication in infants with achondroplasia. It can cause cervicomedullary compression, leading to central apnea and sudden death if not decompressed surgically.

Question 38

A 14-year-old boy undergoes in situ pinning for an unstable slipped capital femoral epiphysis (SCFE). Which of the following is the most common severe complication associated specifically with an unstable SCFE?

Explanation

Unstable SCFE, defined as the inability to bear weight even with crutches, carries a high risk of osteonecrosis (up to 47%). This is compared to a nearly 0% osteonecrosis rate in stable SCFE.

Question 39

A 4-year-old child successfully treated with the Ponseti method for idiopathic clubfoot presents with a relapse characterized by dynamic supination during the swing phase of gait. Which of the following is the most appropriate management?

Explanation

Relapsing dynamic supination in a Ponseti-treated clubfoot is best managed by a period of corrective casting to achieve a plantigrade foot, followed by a full transfer of the anterior tibial tendon to the lateral cuneiform.

Question 40

A 3-year-old girl presents with severe bilateral genu varum. Radiographs demonstrate a sharp angular deformity at the medial proximal tibial metaphysis with a metaphyseal-diaphyseal angle of 20 degrees. What is the most likely diagnosis?

Explanation

A metaphyseal-diaphyseal angle greater than 16 degrees strongly suggests infantile Blount disease (tibia vara) rather than physiologic bowing. This condition requires brace treatment or surgical realignment.

Question 41

Which Salter-Harris fracture classification describes a fracture line that extends through the epiphysis, crosses the physis, and exits through the metaphysis?

Explanation

A Salter-Harris Type IV fracture crosses the epiphysis, physis, and metaphysis. Because it is intra-articular and disrupts the growth plate, anatomic reduction is required to prevent growth arrest.

Question 42

A 5-year-old boy with multiple fragility fractures and blue sclerae is diagnosed with osteogenesis imperfecta. Which pharmacological therapy is the current standard of care to decrease fracture frequency and improve bone mineral density?

Explanation

Intravenous bisphosphonates, such as pamidronate, inhibit osteoclast activity. They have been shown to significantly reduce fracture rates and increase bone density in children with osteogenesis imperfecta.

Question 43

A 3-year-old boy sustains an isolated midshaft femur fracture after a low-energy fall. Examination reveals 1.5 cm of shortening. What is the most appropriate definitive management?

Explanation

For children aged 6 months to 5 years with a femur fracture and acceptable shortening (typically <2 cm), a Spica cast is the gold standard of treatment. Rigid nailing in this age is contraindicated due to the risk of avascular necrosis.

Question 44

A 10-year-old girl presents with a painless "clunk" in her lateral knee during extension. MRI confirms an asymptomatic complete discoid lateral meniscus without any tears. What is the recommended management?

Explanation

An incidental, asymptomatic discoid meniscus does not require prophylactic surgical intervention. Observation is the standard of care unless the patient develops pain, mechanical locking, or a meniscal tear.

Question 45

A 13-year-old boy sustains a twisting ankle injury resulting in a juvenile Tillaux fracture. Avulsion by which of the following ligaments is primarily responsible for this specific fracture pattern?

Explanation

The juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It is caused by avulsion of the anterior inferior tibiofibular ligament (AITFL) as the physis closes asymmetrically.

Question 46

A 6-year-old girl presents with an extension-type, Gartland III supracondylar fracture of the humerus with posteromedial displacement of the distal fragment. Which nerve is most commonly injured in this specific displacement pattern?

Explanation

In posteromedially displaced extension-type supracondylar fractures, the proximal humerus fragment is displaced anterolaterally. This makes the radial nerve the most commonly injured structure.

Question 47

A 15-year-old gymnast presents with chronic mechanical low back pain exacerbated by extension. Radiographs are normal, but an MRI demonstrates bone marrow edema in the L5 pars interarticularis without a fracture line. What is the most appropriate initial management?

Explanation

Bone marrow edema in the pars represents an early stress reaction (pre-spondylolysis). Initial treatment involves conservative management, specifically cessation of sports, rest, and often an antilordotic brace to allow healing.

Question 48

A 12-year-old boy presents with rigid flat feet and recurrent ankle sprains. CT imaging reveals a talocalcaneal coalition. Which of the following clinical signs is most classic for this condition on physical examination?

Explanation

Tarsal coalitions classically present with a rigid flatfoot and markedly decreased subtalar motion. Patients often exhibit "peroneal spastic flatfoot" due to reflex muscle spasm in the peroneal musculature.

Question 49

A 3-year-old girl is brought to the ED holding her right arm pronated and flexed at the side after her father pulled her up by the wrist. Radiographs are unremarkable. What is the precise anatomic structure involved in this pathology?

Explanation

This presentation is classic for "Nursemaid's elbow," a subluxation of the radial head. It occurs when the annular ligament slips over the radial head and becomes interposed in the radiocapitellar joint.

Question 50

A 2-year-old child presents with an interphalangeal joint flexion deformity of the right thumb. A nodule is palpable at the volar MCP joint, and passive extension is impossible. What is the recommended treatment at this age if nonoperative measures have failed?

Explanation

Pediatric trigger thumb is caused by a size mismatch between the FPL tendon (Notta's nodule) and the A1 pulley. Surgical release of the A1 pulley is the definitive treatment if stretching and observation fail.

Question 51

A 10-year-old girl is projected to have a 3.5 cm leg length discrepancy at skeletal maturity due to a prior distal femoral physeal arrest. Her current bone age matches her chronological age. Which of the following is the most appropriate surgical management?

Explanation

For projected discrepancies between 2 and 5 cm, contralateral epiphysiodesis is the standard of care. Because the discrepancy originates in the femur, performing a distal femoral epiphysiodesis on the longer leg is the most appropriate choice.

Question 52

During the treatment of Developmental Dysplasia of the Hip (DDH) with a Pavlik harness, excessive hyperflexion of the hips can lead to which of the following complications?

Explanation

Excessive hyperflexion in a Pavlik harness compresses the femoral nerve against the inguinal ligament, leading to nerve palsy. Excessive abduction, on the other hand, is associated with avascular necrosis of the femoral head.

Question 53

A 10-year-old boy with chronic kidney disease presents with a stable slipped capital femoral epiphysis (SCFE) of the left hip. After in situ pinning of the left hip, what is the most appropriate management for the asymptomatic right hip?

Explanation

Prophylactic pinning of the contralateral hip is highly recommended in SCFE patients with endocrine disorders or renal failure due to the very high risk of bilateral involvement. Observation may be appropriate for selected idiopathic cases, but not metabolic cases.

Question 54

In the Herring lateral pillar classification for Legg-Calve-Perthes disease, a Group B classification indicates what degree of lateral pillar height maintenance?

Explanation

In the Herring classification, Group A has no lateral pillar involvement. Group B maintains > 50% of the lateral pillar height, and Group C has < 50% lateral pillar height maintained.

Question 55

The pathogenesis of achondroplasia is caused by a mutation in the FGFR3 gene resulting in which of the following cellular effects?

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3. This overactivity abnormally inhibits chondrocyte proliferation in the proliferative zone of the physis, leading to short-limb dwarfism.

Question 56

A 12-year-old boy presents with rigid flatfeet and recurrent ankle sprains. Radiographs reveal the "anteater nose" sign. Which of the following is the most likely diagnosis?

Explanation

The "anteater nose" sign is seen on the lateral radiograph and represents an elongation of the anterior process of the calcaneus, which is pathognomonic for a calcaneonavicular coalition. Talocalcaneal coalitions are often indicated radiographically by the "C sign".

Question 57

A 7-year-old child with spastic diplegic cerebral palsy demonstrates an equinus gait pattern. The Silfverskiold test reveals limited ankle dorsiflexion with the knee extended, but normal dorsiflexion with the knee flexed. Which surgical intervention is most appropriate?

Explanation

The Silfverskiold test differentiates isolated gastrocnemius contracture from combined gastrocnemius-soleus contracture. Improvement in dorsiflexion with knee flexion indicates an isolated gastrocnemius contracture, best treated with a gastrocnemius recession.

Question 58

A 6-year-old patient with Morquio syndrome (Mucopolysaccharidosis Type IVA) requires orthopedic clearance before a general anesthetic for dental surgery. Which of the following radiographic studies is most critical to obtain?

Explanation

Patients with Morquio syndrome frequently have odontoid hypoplasia and severe atlantoaxial instability. Flexion-extension cervical spine radiographs are critical to evaluate for instability to avoid catastrophic neurologic injury during intubation.

Question 59

When evaluating an infant for developmental dysplasia of the hip (DDH) using the Graf ultrasound method, the alpha angle evaluates which of the following structures?

Explanation

The alpha angle measures the concavity of the bony acetabular roof (ilium) relative to the straight iliac border. An alpha angle > 60 degrees is considered normal and is classified as Graf Type I.

Question 60

A 4-year-old boy treated successfully in infancy for a right clubfoot with the Ponseti method presents with recurrent dynamic supination of the foot during the swing phase of gait. Passive range of motion is normal. What is the surgical treatment of choice?

Explanation

Dynamic supination in a previously corrected clubfoot is a classic presentation of relapse. If the foot remains passively correctable, a full tibialis anterior tendon transfer (TATT) to the lateral cuneiform is the treatment of choice to balance the foot.

Question 61

A newborn presents with short-limbed dwarfism, bilateral "hitchhiker" thumbs, cauliflower ears, and severe rigid clubfeet. What is the mode of inheritance for this condition?

Explanation

The clinical presentation describes diastrophic dysplasia, which is caused by a defect in the SLC26A2 sulfate transporter. It is inherited in an autosomal recessive manner.

Question 62

A patient with Klippel-Feil syndrome is noted to have congenital fusion of the cervical vertebrae. Which of the following evaluations is highly recommended due to common associated anomalies?

Explanation

Klippel-Feil syndrome is associated with several anomalies, notably genitourinary abnormalities (occurring in up to 30% of patients), congenital heart defects, and Sprengel deformity. A renal ultrasound is routinely recommended to check for an absent or horseshoe kidney.

Question 63

Children with severe Osteogenesis Imperfecta (Type III) are commonly treated with intravenous bisphosphonates. This medication primarily exerts its effect by which of the following mechanisms?

Explanation

Bisphosphonates are analogues of inorganic pyrophosphate that inhibit bone resorption by promoting osteoclast apoptosis. This increases overall bone mineral density and reduces fracture rates in patients with osteogenesis imperfecta.

Question 64

A 13-year-old obese male presents with acute severe groin pain and inability to bear weight after a minor fall. Radiographs show a severe, unstable slipped capital femoral epiphysis (SCFE). Intraoperative forceful reduction of the slip is avoided primarily to prevent which of the following?

Explanation

Forceful reduction or manipulation of an unstable SCFE significantly increases the risk of stretching or tearing the vulnerable posterior retinacular vessels, leading to avascular necrosis (AVN) of the femoral head. In situ pinning without forceful reduction is standard.

Question 65

A 3-year-old child presents with severe bowing of the legs, short stature, and a waddling gait. Laboratory tests reveal normal serum calcium, very low serum phosphate, normal PTH, and elevated alkaline phosphatase. Genetic testing shows a mutation in the PHEX gene. What is the primary pathophysiologic mechanism of this disorder?

Explanation

The presentation describes X-linked hypophosphatemic rickets caused by a PHEX gene mutation. This defect leads to excessive circulating levels of FGF23, which promotes massive renal phosphate wasting and inhibits calcitriol synthesis.

Question 66

In a child with congenital coxa vara, surgical correction with a valgus producing proximal femoral osteotomy is universally indicated when the Hilgenreiner-epiphyseal (H-E) angle exceeds:

Explanation

Surgery is strictly indicated for congenital coxa vara when the Hilgenreiner-epiphyseal (H-E) angle is greater than 60 degrees due to the high risk of progression. Angles between 45 and 59 degrees are typically observed, while those < 45 degrees often resolve spontaneously.

Question 67

A 2-year-old child with multiple café-au-lait spots and axillary freckling presents with anterolateral bowing of the tibia. This orthopedic manifestation is notoriously associated with which of the following complications?

Explanation

Anterolateral bowing of the tibia is highly associated with Neurofibromatosis Type 1 (NF1) and often progresses to congenital pseudoarthrosis of the tibia. Once fractured, these lesions are notoriously difficult to heal and frequently require complex vascularized grafts or amputation.

Question 68

In a 6-year-old boy diagnosed with Duchenne Muscular Dystrophy (DMD), the administration of systemic corticosteroids is aimed primarily at achieving which of the following?

Explanation

Systemic corticosteroids are a mainstay of medical therapy for Duchenne Muscular Dystrophy. They have been shown to prolong independent ambulation, preserve pulmonary function, and delay the onset of severe scoliosis.

Question 69

A 12-year-old boy presents with a left Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

Explanation

Prophylactic pinning of the contralateral hip is highly recommended in patients with endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) due to the high risk of bilateral involvement. Age less than 10 or greater than 16 also increases the risk of bilaterality.

Question 70

An infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). Excessive flexion of the hips in the harness increases the risk of which of the following complications?

Explanation

Excessive flexion of the hip in a Pavlik harness can cause femoral nerve palsy, which manifests as decreased active knee extension. Conversely, excessive abduction places the vascular supply at risk, leading to avascular necrosis.

Question 71

In Legg-Calvé-Perthes disease, which of the following radiographic findings (from the lateral pillar classification) is most predictive of the long-term outcome?

Explanation

The Herring lateral pillar classification, based on the height of the lateral pillar of the capital femoral epiphysis during the fragmentation stage, is the most accurate prognostic indicator for long-term outcome in Legg-Calvé-Perthes disease.

Question 72

A 6-year-old boy sustains an extension-type supracondylar fracture of the humerus. Which nerve is most commonly injured in this specific type of fracture overall?

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. It is a motor branch of the median nerve that controls the flexor pollicis longus and the flexor digitorum profundus to the index finger.

Question 73

A 4-year-old child previously treated for idiopathic clubfoot with the Ponseti method presents with dynamic supination deformity during the swing phase of gait. There is no fixed deformity. What is the most appropriate next step in management?

Explanation

Dynamic supination during the swing phase in a previously corrected clubfoot is typically caused by a strong tibialis anterior acting on a flexible foot. The standard treatment is transferring the tibialis anterior tendon to the lateral cuneiform to balance the foot.

Question 74

Which of the following parameters is the most critical to monitor for hip displacement in a child with spastic quadriplegic cerebral palsy?

Explanation

Reimer's migration percentage is the standard radiographic measurement used to monitor hip subluxation in children with cerebral palsy. A migration percentage greater than 30% typically prompts consideration for surgical intervention to prevent complete dislocation.

Question 75

A 14-year-old boy presents with a rigid flatfoot and recurrent ankle sprains. Radiographs show a "C sign" on the lateral view. Which of the following is the most appropriate initial diagnostic imaging to characterize this specific condition?

Explanation

The "C sign" on a lateral radiograph indicates a talocalcaneal coalition. A CT scan of the hindfoot (specifically coronal views) is the gold standard to clearly delineate the extent and location of a talocalcaneal coalition for surgical planning.

Question 76

An infant with achondroplasia presents with hypotonia, central apnea, and hyperreflexia. Which of the following is the most likely cause of these symptoms?

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis, which can cause cervicomedullary compression leading to central apnea, hypotonia, and sudden death. Urgent neurosurgical decompression is indicated if the patient is symptomatic.

Question 77

A 2-year-old obese girl presents with bilateral bowing of the legs. Radiographs demonstrate an abrupt sharp angulation of the medial proximal tibial metaphysis with a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees. What is the most appropriate management?

Explanation

For early-onset (infantile) Blount's disease in children under age 3 with Langenskiöld stage I or II, bracing with a KAFO is the initial treatment of choice. A metaphyseal-diaphyseal angle >16 degrees strongly suggests true Blount disease rather than physiologic bowing.

Question 78

A 13-year-old girl sustains a Salter-Harris type III fracture of the anterolateral aspect of the distal tibial epiphysis. The mechanism of this injury is primarily due to avulsion by which of the following structures?

Explanation

A juvenile Tillaux fracture is an avulsion of the anterolateral distal tibial epiphysis caused by tension from the anterior inferior tibiofibular ligament (AITFL). It occurs in adolescents because the central and medial physes close before the anterolateral aspect.

Question 79

A 5-year-old boy with a history of recurrent fractures and blue sclerae is diagnosed with Osteogenesis Imperfecta type I. Which of the following medical treatments has been shown to most effectively decrease fracture incidence and increase bone mineral density in this population?

Explanation

Intravenous bisphosphonates, such as pamidronate, have been shown to significantly reduce fracture rates, alleviate bone pain, and increase vertebral bone mineral density in children with osteogenesis imperfecta.

Question 80

A 2-month-old infant is noted to have a right-sided congenital muscular torticollis. The head is tilted to the right and rotated to the left. Which of the following conditions has the highest rate of association with this presentation and requires mandatory screening?

Explanation

Congenital muscular torticollis has a well-known association with developmental dysplasia of the hip (DDH), occurring in up to 20% of cases. All infants presenting with muscular torticollis must undergo screening for DDH.

Question 81

A 13-year-old boy undergoes in situ single-screw fixation for a stable slipped capital femoral epiphysis (SCFE). Which of the following is the most common major complication if the screw penetrates the joint anteriorly and is left unrecognized?

Explanation

Chondrolysis is a devastating complication in SCFE management, frequently caused by unrecognized hardware penetration into the joint space. Proper fluoroscopic evaluation with an approach-withdrawal technique is crucial to ensure the screw is entirely within the bone.

Question 82

A 4-year-old girl presents with congenital scoliosis secondary to a fully segmented hemivertebra at T8. The curve has progressed by 15 degrees over the past year. What is the most appropriate definitive management?

Explanation

Congenital scoliosis caused by a fully segmented hemivertebra carries a high risk of rapid progression and does not respond to bracing. The definitive treatment of choice for a progressing, isolated fully segmented hemivertebra is excision and short-segment fusion.

Question 83

A 2-year-old girl is diagnosed with a neglected left developmental dysplasia of the hip (DDH). The hip is completely dislocated. Which of the following surgical strategies is most likely necessary to achieve a stable, concentric reduction?

Explanation

In children older than 18-24 months with a completely dislocated DDH, open reduction is almost universally required. Femoral shortening osteotomy is typically necessary to relieve soft tissue tension, and a pelvic osteotomy is needed to correct acetabular dysplasia.

Question 84

A 3-year-old child sustains an isolated spiral fracture of the midshaft femur. There is no suspicion of non-accidental trauma, and shortening is less than 2 cm. Which of the following is the standard of care for definitive treatment?

Explanation

For a preschool-aged child (under 5 years) with a typical isolated closed femur shaft fracture and acceptable shortening, early hip spica casting is the gold standard treatment with excellent remodeling potential.

Question 85

A 6-year-old boy presents with right hip pain, a limp, and limited internal rotation. Radiographs demonstrate a subchondral radiolucent line in the anterolateral aspect of the femoral head. What is this sign called and what does it indicate?

Explanation

The subchondral radiolucent line is the "crescent sign", representing a subchondral fracture occurring in the early stages of avascular necrosis, such as Legg-Calvé-Perthes disease. It typically dictates the extent of epiphyseal involvement.

Question 86

A 9-year-old girl is incidentally found to have a discoid lateral meniscus on MRI after mild knee trauma. She denies any popping, catching, or mechanical symptoms. What is the most appropriate management?

Explanation

An asymptomatic discoid meniscus without a tear should be managed with observation alone. Surgical intervention, such as saucerization, is only indicated if the patient develops persistent symptoms, pain, or mechanical locking due to a tear.

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