Question 1

A 7-year-old boy has short stature, unilateral coxa vara, and lack of ossification in the medial pubic rami. The most likely diagnosis is:

Explanation

Cleidocranial dysplasia produces the above findings, in addition to partial or complete lack of formation of the clavicles and persistent widening of the cranial fontanelles. None of these findings are present in the other conditions.

Question 2

An 11-year-old girl injures her knee while playing lacrosse and develops a hemarthrosis. The most likely diagnosis is:

Explanation

The most common cause of hemarthrosis of the knee in skeletally immature patients is a patellar dislocation. Anterior cruciate ligament injuries and tibial spine avulsions are less common. Medial meniscus tears are extremely rare in this population.

Question 3

In order to see the articular cartilage of the knee in a child who has knee trauma, a magnetic resonance image must include:

Explanation

Articular cartilage may be injured during trauma to the knee and manifest as either osteochondral fractures or osteochondritis dissecans. The articular cartilage is best visualized using gradient echo sequences. Examples of this technique include fast lowangle shot (FLASH) imaging, fast imaging with steady precession (FISP), and short tau inversion recovery (STIR).

Question 4

For a patient who has thoracic idiopathic scoliosis of the surgical range, the distance between the thecal sac and the apical thoracic pedicle on the concave side is:

Explanation

The distance between the apical thoracic pedicle and the thecal sac is less than 1 mm on the concave side.

Question 5

Which region (vertebral body) of the spine is the closest to the aorta:

Explanation

The aorta is on the left side of the vertebra in the upper and midthoracic spine. The aorta moves to an anterior location in the lower thoracic spine. The distance from the aorta to the vertebral body is 6 mm to 7 mm in skeletally mature patients with idiopathic scoliosis between the fourth and ninth vertebral bodies. The distance becomes less than 5 mm in the thoracolumbar junction and lumbar spine. The aortic arch does not extend to the first thoracic vertebral.

Question 6

The width of the pedicles in a patient with idiopathic scoliosis in the surgical range is narrowest in the:

Explanation

The width of the pedicles is less in the thoracic spine than in the lumbar or sacral spine, and less on the concavity than on the convexity. The mean width of the thoracic pedicles on the concave side at the apex in skeletally mature patients is only 3 mm.

Question 7

The angle of the pedicle with the midsagittal plane at T11 is closest to:

Explanation

The angle of the pedicles is greatest in the upper thoracic and lumbar spines (approximately 15°). The angle decreases to approximately 7° at the thoracolumbar junction.

Question 8

Which of the following is not a common finding in the forearms of patients who have multiple hereditary exostoses:

Explanation

Multiple hereditary exostosis is characterized by differential growth of the two bones. There is often decreased length of the ulna. This results in increased inclination of the distal radial articular surface, radial head subluxation, and subluxation of the carpus toward the ulna. The exostoses themselves may block rotation.

Question 9

Which of the following factors has proven to increase the risk of degenerative disease of the wrist in patients with multiple hereditary osteochondromas:

Explanation

The above findings are all more common in the forearms and wrists of patients with multiple hereditary exostoses than in the general population. However, there is no parameter shown to increase the risk of degenerative wrist disease.

Question 10

Which adverse outcome is most common in adults undergoing periacetabular osteotomy for hip dysplasia:

Explanation

Heterotopic ossification occurs in fewer than 5% of patients undergoing various types of periacetabular osteotomy. Femoral nerve palsy and sciatic nerve palsy occur in only 1% to 2% of patients. Nonunion is rare in this region because of abundant cancellous bone contact. Persistent or worsening joint pain is the most frequent adverse outcome and is least common in those patients with preoperative degenerative changes.

Question 11

An 18-year-old woman complains of pain in her groin area. An anteroposterior radiograph reveals a dysplastic hip with a centeredge angle of 0°. The femoral head is spherical and centers better on abduction. There is a cyst in the superior acetabulum. The joint space is narrowed superiorly by 1 mm. Recommended treatment includes:

Explanation

This patient has a high likelihood of progressive hip deterioration so surgery is warranted. The periacetabular osteotomy is preferred because the procedure can correct this high degree of hip dysplasia. The Salter osteotomy, which hinges the hemipelvis on the symphysis pubis, cannot reliably correct more than 10° of dysplasia in this age group. The Pemberton osteotomy relies on plasticity of the immature skeleton to â foldâ the pelvis on an open triradiate cartilage, therefore, it is not indicated in an 18-yearold woman who is skeletally mature. Hip arthrodesis is not indicated when there are other, better options. The same can be said for total hip arthroplasty due to the finite duration of fixation in a young person.

Question 12

A high school basketball player dies suddenly during a game. Which of the following is the least likely cause of death:

Explanation

Hypertrophic cardiomyopathy, coronary artery anomalies, and electrical abnormalities are the most common causes of sudden death in athletes. Substance abuse is also common. Marfan syndrome, which can be heralded by skeletal features of arachnodactyly, should also be considered when screening athletes although it is not as likely as the other choices to cause death.

Question 13

A 15-year-old girl has anterior hip pain and she tells you that she hears periodic snapping or clicking. Bringing the hip from the flexed-abducted position to the extended position reproduces the pain. Radiographs are normal. The diagnosis is most likely:

Explanation

Snapping of the psoas tendon is more common in girls than boys. A snapped psoas tendon is characterized by anterior hip pain that can be reproduced by moving the hip from a figure 4 position to an extended position. The discomfort from trochanteric bursitis is located laterally. The symptoms of an abnormality in the labrum or the acetabulum are not associated with snapping.

Question 14

A 15-year-old girl has a snapping psoas tendon. Abducting and adducting her hip reproduces symptoms of anterior hip pain. Her pain has not been relieved by rest and stretching. The next step of treatment is:

Explanation

The initial treatment of snapping psoas tendon is rest, antiinflammatory agents, and stretching. If symptoms remain significant, the next measure to offer the patient is intramuscular lengthening of the tendon.

Question 15

A 4-year-old girl is newly diagnosed with developmental dislocations of the hips. The femoral heads are fully dislocated and located 4 cm above the acetabulum. No pseudoacetabulum is seen. Recommended treatment includes:

Explanation

At the age of 4, femoral shortening is indicated to remove the pressure on the reduced femoral head. Realignment of the bony dysplasia is achieved by femoral derotation, iliac redirection, and possible creation of varus in the proximal femur. Open reduction through a medial approach is an option during the first 2 years, but after that the anterolateral approach is preferred in order to create a stable capsulorrhaphy.

Question 16

A 3-year-old boy falls from a swing and injures his elbow. Radiographs show posteromedial displacement of the radius and ulna. A small fleck of bone is viewed on the radiograph that does not match the contralateral elbow. The most likely diagnosis is:

Explanation

Isolated elbow dislocations are rare in very young children because the epiphysis is mostly cartilaginous. Supracondylar fractures usually occur at an older age and have an obvious fracture line. A Salter I injury does not have an osseous component. A radial head fracture-dislocation would not explain the disruption of the ulna-humerus articulation. A lateral condyle fracture-dislocation is the most likely diagnosis in this patient.

Question 17

A 6-month-old baby is brought in for consultation because of bowing of the tibia and fibula. The apex of the bow is medial and posterior. The angulation measures 40° on the anteroposterior film and 35° on the lateral film. One of the babys legs is 1.5 cm shorter than the other one. Recommended treatment includes:

Explanation

Posteromedial bowing of the tibia is not likely to go on to fracture. In most cases, the bowing resolves with growth. The length inequality remains proportionate throughout growth. No treatment is indicated at this time. Length equalization by standard means is indicated near maturity.

Question 18

Which of the following bone lesions is shown to improve radiographically and clinically by use of systemic medication:

Explanation

In patients with polyostotic fibrous dysplasia, there is a decrease in pain and fracture rate and an improvement in radiodensity through the use of bisphosphonates. None of the other lesions mentioned respond radiographically to systemic medication.

Question 19

Polyostotic fibrous dysplasia is caused by a mutation in which of the following genes:

Explanation

Fibrous dysplasia is due to a postzygotic mutation in the GNAS1 gene. By contrast, EXT 1 mutations can cause multiple exostoses, and fibroblast growth factor receptor protein mutations cause achondroplasia, among other disorders. C FBA1 mutations are responsible for cleidocranial dysplasia. C OL1A1 mutations are responsible for osteogenesis imperfecta.

Question 20

A 17-year-old girl is newly diagnosed with an expansile lesion of the distal tibia that is causing pain. Radiographs and biopsy are consistent with an aneurysmal bone cyst. Recommended treatment includes:

Explanation

Aneurysmal bone cyst is a progressively expansile lesion that does not involute with time. Treatment of aneurysmal bone cysts is curettage and bone graft. Wide resection and structural allografts have a high complication rate and are not indicated for initial treatment. Injection of marrow or steroids is effective for unicameral cysts, but not for aneurysmal cysts. Local radiation is indicated only as an adjunct for lesions that are not surgically resectable.

Question 21

A 12-year-old obese boy presents with right thigh pain and a limp for 3 weeks. Examination reveals obligatory external rotation of the right hip during passive flexion. Radiographs demonstrate a 'slip' of the capital femoral epiphysis. What is the most appropriate initial treatment?

Explanation

The patient has a stable slipped capital femoral epiphysis (SCFE). The standard of care is in situ fixation with a single cannulated screw placed in the center of the epiphysis.

Question 22

A 3-month-old girl is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. During a follow-up visit, the parents report she has stopped kicking her left leg, and you note an absence of active knee extension. What is the most appropriate next step in management?

Explanation

Decreased active knee extension in a Pavlik harness indicates a femoral nerve palsy caused by hyperflexion of the hip. The harness must be removed or adjusted immediately to allow recovery of nerve function.

Question 23

In the Ponseti method for treating idiopathic clubfoot, which of the following represents the correct sequence of deformity correction?

Explanation

The sequence of correction in the Ponseti method follows the acronym CAVE: Cavus, Adductus, Varus, and finally Equinus.

Question 24

A 4-year-old child presents with worsening bilateral bowing of the legs. Radiographs reveal a sharp metaphyseal beak and a metaphyseal-diaphyseal angle of 18 degrees. What is the most likely diagnosis?

Explanation

A metaphyseal-diaphyseal angle greater than 16 degrees in a child with tibial bowing strongly suggests infantile Blount disease rather than physiologic genu varum.

Question 25

A 6-year-old boy sustains a supracondylar humerus fracture that is displaced posterolaterally. Which nerve is at the highest risk of injury in this specific displacement pattern?

Explanation

Posterolaterally displaced supracondylar humerus fractures stretch the medial structures, putting the anterior interosseous nerve (AIN) and brachial artery at highest risk.

Question 26

A 13-year-old boy complains of recurrent ankle sprains and lateral foot pain. Examination shows a rigid flatfoot and peroneal spasticity. Computed tomography demonstrates a talocalcaneal coalition. Which facet is most commonly involved?

Explanation

Talocalcaneal coalitions most frequently involve the middle facet of the subtalar joint. This presents as a rigid, painful flatfoot in early adolescence.

Question 27

A newborn presents with multiple fractures and blue sclerae. Genetic testing confirms Osteogenesis Imperfecta (OI). This condition is primarily caused by a mutation affecting which of the following?

Explanation

Osteogenesis Imperfecta is typically caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode for Type I collagen.

Question 28

A 12-year-old boy presents with a painful, snapping knee. MRI reveals a Wrisberg variant of a discoid lateral meniscus. This specific variant is hypermobile because it lacks which of the following normal anatomical attachments?

Explanation

The Wrisberg variant of the discoid lateral meniscus lacks the normal posterior meniscotibial (coronary) ligament attachments, making it highly mobile and prone to snapping.

Question 29

A 14-year-old boy sustains an inversion ankle injury. Radiographs show a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. The avulsed fragment is attached to which of the following ligaments?

Explanation

This describes a juvenile Tillaux fracture. The fracture occurs due to an avulsion by the anterior inferior tibiofibular ligament (AITFL) as the medial physis closes before the lateral physis.

Question 30

Which of the following is the most common anatomical location for Osteochondritis Dissecans (OCD) in the pediatric knee?

Explanation

The classic and most common location for Osteochondritis Dissecans (OCD) of the knee is the lateral aspect of the medial femoral condyle.

Question 31

A 6-year-old boy has a history of delayed motor milestones and pseudohypertrophy of the calves. He uses his hands to climb up his legs when rising from the floor (Gowers' sign). A muscle biopsy would most likely show an absence of which protein?

Explanation

The clinical presentation is classic for Duchenne Muscular Dystrophy (DMD). DMD is an X-linked recessive disorder characterized by the absence of the protein dystrophin.

Question 32

A 5-year-old boy presents with a limp and hip pain. Radiographs demonstrate sclerosis and fragmentation of the proximal femoral epiphysis. Which radiographic sign is considered a 'head-at-risk' sign in Legg-Calve-Perthes disease?

Explanation

The Gage sign (a V-shaped radiolucency in the lateral portion of the epiphysis and adjacent metaphysis) is a classic 'head-at-risk' sign indicating potential for poor outcomes in Perthes disease.

Question 33

A 4-year-old presents with fever, inability to bear weight on the right leg, a white blood cell count of 14,000/mm3, and an erythrocyte sedimentation rate (ESR) of 50 mm/hr. According to the Kocher criteria, what is the probability of septic arthritis?

Explanation

The patient meets all 4 Kocher criteria (fever, non-weight-bearing, WBC >12,000, ESR >40). The probability of septic arthritis with 4 positive predictors is 93-99%.

Question 34

A newborn is diagnosed with a congenital vertical talus. Which of the following is the defining pathological anatomic relationship in this condition?

Explanation

Congenital vertical talus is characterized by a rigid rocker-bottom deformity caused by the irreducible dorsal dislocation of the navicular on the neck of the talus.

Question 35

A 9-year-old boy with a midshaft femur fracture is treated with flexible intramedullary nails. He presents 6 months later with a 1.5 cm leg length discrepancy (treated leg is longer). What is the primary mechanism for this finding?

Explanation

Pediatric femur fractures often undergo a period of overgrowth (typically 1-2 cm) due to fracture hyperemia stimulating the proximal and distal physes. This effect is most prominent in children aged 2 to 10 years.

Question 36

A 1-year-old boy presents with an infantile idiopathic scoliosis curve measuring 30 degrees. Which radiographic measurement is the most reliable prognostic indicator for curve progression?

Explanation

Mehta's Rib-Vertebral Angle Difference (RVAD) is the most critical prognostic factor for infantile idiopathic scoliosis. An RVAD greater than 20 degrees strongly predicts curve progression.

Question 37

A 10-year-old boy with open physes sustains a complete anterior cruciate ligament (ACL) tear. To minimize the risk of growth arrest, a physeal-sparing reconstruction is planned. Which autograft is most commonly used for this specific extra-articular/intra-articular technique?

Explanation

The iliotibial (IT) band is frequently used in physeal-sparing ACL reconstructions (such as the Micheli or Kocher techniques) in prepubescent children to avoid drilling across the open physes.

Question 38

A 14-year-old gymnast complains of chronic lower back pain. Radiographs show a grade II spondylolisthesis at L5-S1. What radiographic parameter is most predictive of future slip progression?

Explanation

The slip angle (sagittal roll or kyphosis) is the most important radiographic predictor for the progression of a dysplastic spondylolisthesis. High slip angles indicate greater instability.

Question 39

A child with cerebral palsy (GMFCS Level IV) is noted to have lateral subluxation of the hip on AP pelvic radiographs. The Reimers migration index is measured at 45%. What is the most appropriate management?

Explanation

In cerebral palsy patients, a Reimers migration index >40% typically requires bony reconstructive surgery (VDRO and pelvic osteotomy) because soft tissue releases alone are insufficient to reliably stabilize the hip.

Question 40

A neonate is found to have bilateral posteromedial bowing of the tibia. Which of the following conditions is most commonly associated with this specific type of tibial bowing?

Explanation

Posteromedial bowing of the tibia in a newborn is typically benign and is strongly associated with a calcaneovalgus foot deformity. Unlike anterolateral bowing, it does not lead to pseudoarthrosis and often resolves spontaneously.

Question 41

A 13-year-old obese male presents with acute worsening of chronic left hip pain. On examination, he has an obligatory external rotation of the hip during passive flexion. Radiographs demonstrate a severe, unstable slipped capital femoral epiphysis (SCFE). What is the most severe and frequent complication specifically associated with an unstable SCFE?

Explanation

Unstable SCFE carries a significantly higher risk of avascular necrosis (AVN) of the femoral head, with rates up to 50%. Chondrolysis is more commonly associated with prominent hardware following in situ pinning.

Question 42

A 3-month-old female is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. Her parents report that she is no longer actively extending her knee on the treated side. Which of the following nerve palsies is most likely occurring?

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, typically occurring when the hip is in hyperflexion. The harness should be adjusted or discontinued until active quadriceps function returns.

Question 43

In a 6-year-old boy diagnosed with Legg-Calve-Perthes disease, the Herring lateral pillar classification is used to determine prognosis. A Type B classification indicates that what percentage of the lateral pillar height is maintained on the anteroposterior radiograph?

Explanation

According to the Herring classification, Type B is defined by the maintenance of >50% of the lateral pillar height. Type C indicates <50% height maintenance, portending a worse prognosis.

Question 44

A 4-year-old boy sustains a closed, displaced midshaft femur fracture. He is planned for conservative management in a hip spica cast. What is the maximum acceptable amount of shortening in this patient to allow for the anticipated overgrowth phenomenon?

Explanation

In children aged 2 to 10 years, femoral overgrowth after a shaft fracture is expected. An initial shortening of 1.5 to 2.0 cm is considered acceptable and often resolves completely.

Question 45

A 5-year-old girl falls from monkey bars and sustains an extension-type supracondylar humerus fracture. On examination, which finding is most indicative of the most commonly injured nerve in this specific fracture pattern?

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. Injury is assessed by the inability to flex the IP joint of the thumb and the DIP joint of the index finger (the 'OK' sign).

Question 46

An infant with idiopathic clubfoot is undergoing serial casting using the Ponseti method. According to the principles of this method, which component of the deformity is corrected first?

Explanation

The Cavus deformity is corrected first in the Ponseti method by elevating the first ray to supinate the forefoot and align it with the hindfoot. Equinus is the final deformity corrected, often requiring a percutaneous Achilles tenotomy.

Question 47

A 14-month-old boy is evaluated for infantile idiopathic scoliosis. Radiographs reveal a left thoracic curve of 25 degrees. Which of the following radiographic parameters is the most reliable predictor of curve progression in this patient?

Explanation

Mehta described the rib-vertebra angle difference (RVAD) for infantile idiopathic scoliosis. An RVAD greater than 20 degrees strongly correlates with progressive curves requiring intervention.

Question 48

A 4-year-old child presents with a history of multiple low-energy fractures and bluish discoloration of the sclerae. Genetic testing would most likely reveal a defect involving the production of which of the following?

Explanation

The clinical presentation is classic for Osteogenesis Imperfecta (OI). OI is primarily caused by mutations in the COL1A1 or COL1A2 genes, which lead to quantitative or qualitative defects in Type I collagen.

Question 49

A 15-year-old male with achondroplasia presents with progressively worsening lower extremity weakness and neurogenic claudication. What is the primary anatomical cause of this complication in achondroplastic patients?

Explanation

Achondroplasia causes impaired endochondral ossification, which leads to abnormally short and thickened pedicles. This results in severe central canal stenosis and neurogenic claudication.

Question 50

A 2-year-old girl is brought to the emergency department with a limp, refusal to bear weight on the right leg, and a fever of 38.2 C. Aspiration of the hip yields purulent fluid. Given the patient's age and contemporary vaccination protocols, which of the following organisms is increasingly recognized as a leading cause of pediatric septic arthritis?

Explanation

Kingella kingae is a fastidious Gram-negative organism that is now considered the most common bacterial cause of septic arthritis in children aged 6 to 36 months in areas with routine Hib and pneumococcal vaccination.

Question 51

A 12-year-old boy sustains a Salter-Harris Type IV fracture of the medial malleolus. The primary orthopaedic rationale for precise, anatomic open reduction and internal fixation of this injury is to prevent which of the following?

Explanation

Salter-Harris IV fractures cross the epiphysis, physis, and metaphysis. Anatomic reduction is mandatory to align the physeal zones and prevent the formation of a bony bar, which leads to growth arrest and angular deformity.

Question 52

An 8-year-old girl complains of a snapping sensation and lateral joint line pain in her right knee. MRI confirms a discoid lateral meniscus. The Wrisberg variant of a discoid meniscus is uniquely characterized by the absence of which of the following structures?

Explanation

The Wrisberg variant of the discoid meniscus lacks the normal posterior meniscotibial (coronary) ligament attachments. It is hypermobile and tethered posteriorly only by the meniscofemoral ligament of Wrisberg.

Question 53

A 12-year-old boy presents with a painful, rigid flatfoot and a history of recurrent ankle sprains. An oblique radiograph of the foot demonstrates the 'anteater nose' sign. Which of the following is the most likely diagnosis?

Explanation

The 'anteater nose' sign is a classic radiographic finding on an oblique view of the foot representing an elongated anterior process of the calcaneus. It is pathognomonic for a calcaneonavicular coalition.

Question 54

A 14-year-old boy sustains a Meyers-McKeever Type III anterior tibial eminence fracture during a bicycle accident. What is the most appropriate management for this specific injury pattern?

Explanation

Meyers-McKeever Type III fractures are completely displaced tibial eminence avulsions. They require surgical intervention (arthroscopic or open) for anatomical reduction and fixation to restore ACL competence.

Question 55

A 3-year-old boy is diagnosed with infantile Blount disease. Radiographs show a Langenskiold stage II lesion of the medial proximal tibia. What is the most appropriate initial management?

Explanation

For children under 4 years of age with Langenskiold stage I or II infantile Blount disease, a bracing regimen with a KAFO is the initial treatment of choice. Surgery is indicated if bracing fails or if the child is older or has advanced staging.

Question 56

A newborn is noted to have a prominent anterolateral bow of the distal tibia. Radiographs show medullary sclerosis and cortical thickening. This condition has the strongest association with which of the following systemic disorders?

Explanation

Congenital anterolateral bowing of the tibia is a precursor to congenital pseudarthrosis of the tibia. It has a strong clinical association with Neurofibromatosis type 1 (NF1).

Question 57

A 4-year-old girl is evaluated for a high-riding, hypoplastic left scapula (Sprengel deformity). During surgical correction via the Woodward procedure, the surgeon must identify and resect an anomalous structure that frequently connects the medial border of the scapula to the cervical spine. What is this structure called?

Explanation

The omovertebral bone (or cartilaginous/fibrous band) connects the cervical spine to the superior medial border of the scapula in about 30% to 50% of patients with Sprengel deformity. Its resection is required to effectively lower the scapula.

Question 58

When evaluating a pediatric patient with a painful hip, the classic Kocher criteria are used to differentiate septic arthritis from transient synovitis. Which of the following is NOT one of the original four parameters described by Kocher?

Explanation

The four classic Kocher criteria are fever >38.5 C, non-weight-bearing status, ESR >40 mm/hr, and WBC >12,000 cells/mm3. Joint space widening on plain films is not part of this specific predictive model.

Question 59

An 11-year-old elite baseball pitcher presents with insidious onset of right shoulder pain during the late cocking phase of throwing. Radiographs demonstrate widening and demineralization of the proximal humeral physis. What is the best initial management for this condition?

Explanation

Little League Shoulder is an epiphysiolysis of the proximal humerus caused by repetitive rotational microtrauma. The foundation of treatment is complete rest from throwing for typically 3 to 6 months until symptoms resolve and radiographs normalize.

Question 60

A 10-year-old boy jumps to catch a basketball and feels a 'pop' in his right knee. On examination, he has a palpable defect inferior to the patella and an extensor lag of 30 degrees. Lateral radiograph reveals a high-riding patella with a small bony fragment inferior to it. What is the most likely diagnosis?

Explanation

A patellar sleeve fracture is a pediatric injury involving avulsion of the unossified distal patellar cartilage along with a small shell of bone. It presents with an extensor lag, patella alta, and a characteristic small inferior pole bony fragment on X-ray.

Question 61

A 13-year-old obese male undergoes in situ pinning for a stable slipped capital femoral epiphysis (SCFE). Six months postoperatively, he presents with severe hip stiffness, pain, and a 50% reduction in joint space on radiographs. No signs of infection are present. What is the most likely diagnosis?

Explanation

Chondrolysis is a known complication of SCFE, characterized by acute cartilage destruction, joint space narrowing to less than 3 mm, and severe stiffness. It can occur secondary to unrecognized pin penetration into the joint or intrinsically from the disease process.

Question 62

In evaluating a 9-year-old boy with Legg-Calvé-Perthes disease, which of the following is the most significant prognostic factor for long-term hip deformity?

Explanation

The two most critical prognostic factors in Legg-Calvé-Perthes disease are the age of onset (worse prognosis if older than 8 years) and the lateral pillar classification (extent of lateral epiphyseal involvement). Older children have less time for spherical remodeling before skeletal maturity.

Question 63

A 6-year-old boy presents with a completely displaced posterolateral supracondylar humerus fracture. Which of the following neurologic deficits is most likely to be observed?

Explanation

Posterolateral displacement of a supracondylar humerus fracture stretches anterior structures, predominantly putting the anterior interosseous nerve (AIN) at risk. AIN palsy presents with weakness in the flexor pollicis longus and flexor digitorum profundus to the index finger, resulting in an inability to make the 'A-OK' sign.

Question 64

When treating idiopathic congenital talipes equinovarus using the Ponseti method, what is the correct sequence of deformity correction?

Explanation

The Ponseti method corrects the deformities of clubfoot in a specific sequence summarized by the acronym CAVE: Cavus (by elevating the first ray), Adductus, Varus, and finally Equinus. The equinus is corrected last, often requiring a percutaneous Achilles tenotomy.

Question 65

A 24-month-old girl is newly diagnosed with developmental dysplasia of the hip (DDH) demonstrating a completely dislocated right hip. What is the most appropriate initial management?

Explanation

In children older than 18 to 24 months with a completely dislocated hip, open reduction is generally required as closed reduction is rarely successful. Concomitant pelvic and femoral shortening osteotomies are frequently necessary to safely reduce the hip without excessive tension that risks avascular necrosis.

Question 66

A 10-year-old boy sustains a Meyers and McKeever Type III anterior tibial spine avulsion fracture. Assuming no meniscal entrapment, what is the primary indication for surgical fixation over cast immobilization?

Explanation

A Type III tibial spine fracture is completely displaced. Surgical reduction and fixation are indicated to restore proper ACL tension, prevent chronic anterior knee instability, and remove any interposed tissue that blocks anatomic reduction.

Question 67

What is the most common anatomical location for osteochondritis dissecans (OCD) in the pediatric knee?

Explanation

The most common location for OCD lesions in the knee is the lateral aspect of the medial femoral condyle, accounting for approximately 70-80% of cases. This typically occurs due to repetitive microtrauma and vascular watershed vulnerability.

Question 68

A 7-year-old child with spastic diplegic cerebral palsy presents for routine follow-up. Pelvic radiographs reveal a Reimers migration percentage of 45% in the left hip. What is the most appropriate management?

Explanation

A Reimers migration percentage greater than 40% in a child with cerebral palsy indicates significant hip subluxation that is unlikely to respond to soft-tissue releases alone. Bony reconstruction with a varus derotational femoral osteotomy (VDRO), often combined with a pelvic osteotomy, is the standard of care to stabilize the hip.

Question 69

A 14-year-old boy presents with a rigid flatfoot, recurrent ankle sprains, and peroneal spasm. Radiographs show the 'anteater nose' sign. Which specific pathology does this radiographic finding represent?

Explanation

The 'anteater nose' sign on an oblique radiograph of the foot represents an elongation of the anterior process of the calcaneus, which is pathognomonic for a calcaneonavicular coalition. This is a common cause of rigid flatfoot and peroneal spastic flatfoot in adolescents.

Question 70

A 4-year-old girl is diagnosed with infantile Blount disease, classified as Langenskiöld stage IV. What is the most appropriate definitive treatment?

Explanation

Langenskiöld stage IV infantile Blount disease involves advanced depression of the medial tibial plateau and is unlikely to respond to bracing or guided growth alone. Proximal tibial realignment osteotomy (often with elevation of the medial plateau) is indicated to prevent progressive deformity and joint degeneration.

Question 71

Achondroplasia is characterized by disproportionate short stature. What is the underlying genetic and cellular mechanism responsible for this dysplasia?

Explanation

Achondroplasia is caused by a gain-of-function mutation in the fibroblast growth factor receptor 3 (FGFR3) gene, inherited in an autosomal dominant pattern. This mutation constitutively activates the receptor, which paradoxically inhibits chondrocyte proliferation in the proliferative zone of the physis.

Question 72

A 6-year-old child presents with severe genu valgum, short stature, and normal intelligence. Radiographs show platyspondyly and odontoid hypoplasia. A deficiency in which of the following enzymes is the most likely cause?

Explanation

Morquio syndrome (MPS IV) presents with normal intelligence, severe skeletal dysplasia, and odontoid hypoplasia. It is caused by a deficiency in galactosamine-6-sulfatase (Type A) or beta-galactosidase (Type B).

Question 73

A 4-year-old boy with rhizomelic short stature has a known mutation in the FGFR3 gene. As this patient reaches adulthood, which of the following spinal abnormalities is most likely to require surgical intervention?

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene. In adulthood, symptomatic lumbar spinal stenosis is common due to anatomically short pedicles and a progressively decreasing interpedicular distance.

Question 74

A 2-year-old child with frequent fractures, blue sclerae, and dentinogenesis imperfecta is started on intravenous pamidronate. What is the primary mechanism of action of this pharmacological treatment?

Explanation

Pamidronate is a nitrogen-containing bisphosphonate used in Osteogenesis Imperfecta to increase bone density and reduce fractures. It functions by inhibiting farnesyl pyrophosphate synthase in osteoclasts, leading to osteoclast apoptosis.

Question 75

During the initial phase of the Ponseti casting technique for the treatment of idiopathic clubfoot, which component of the deformity must be addressed first?

Explanation

The Ponseti method corrects deformities in a specific order summarized by the acronym CAVE: Cavus, Adductus, Varus, then Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot.

Orthopedic Prometric MCQs - Chapter 3 Part 1

Orthopedic Prometric MCQs - Chapter 3 Part 2

Orthopedic Prometric MCQs - Chapter 3 Part 2

Chapter Index