Question 1

Fractures that have a high specificity for child abuse include all of the following except:

Explanation

Even though a spiral pattern suggests a rotational force, spiral fractures of the femur are not specific for abuse. All of the other patterns are highly specific although not absolutely diagnostic.

Question 2

The differential diagnosis of abuse in a child with a long bone fracture includes all of the following conditions except:

Explanation

All of the diagnoses except metaphyseal dysplasia place patients at increased risk of fracture, and therefore could be confused with nonaccidental injury.

Question 3

Among children with nonossifying fibromas, a risk of pathologic fracture exists mainly when a lesion exceeds what minimum percentage of a boneâ s diameter:

Explanation

In a series from the Mayo clinic, all pathologic fractures associated with nonossifying fibromas in the lower extremity occurred in lesions larger than 50% of the transverse diameter.

Question 4

In a bowed tibia, the tensile stress during weightbearing is greatest at which point:

Explanation

The moment becomes tensile at the apex on the convex side of a tibial bow, in contrast to the normal compressive stress in a straight diaphysis. The moment is equal to load multiplied by distance from the axis of load.

Question 5

Which of the following medications has not been shown to increase the risk of osteopenia or osteoporosis:

Explanation

Pamidronate, a bisphosphonate, increases bone density by inhibiting resorption. All of the medications listed as possible answers decrease bone density.

Question 6

A 7-year-old gymnast complains of pain in her medial midfoot. Radiographs reveal that the navicular is narrower and more sclerotic on this side than the other. The midfoot appears somewhat flattened. Your next step is to recommend:

Explanation

The condition described best resembles Kohlerâ s disease, or avascular necrosis of the tarsal navicular. This disease has a natural history of spontaneous improvement with time, and biopsy is not needed. Rest improves symptoms, although it is probably not mandatory. Sometimes with severe pain, a cast may help to speed improvement of symptoms.

Question 7

Which part of the body is removed last in a posterior vertebral column resected via a posterior approach:

Explanation

To protect and stabilize the neural elements, the posterior vertebral cortex is left intact to be resected last.

Question 8

An 18-year-old man has chronic pain in his right thigh, which is foreshortened with an increased anterior bow (Slides). What is the most likely diagnosis:

Orthopedic Prometric Exam Chapter 3 Image

Explanation

This patient has polyostotic fibrous dysplasia. The diffuse enlargement in width is atypical for osteogenesis imperfecta or infection. Pagets disease is associated with increased sclerosis. Enchondromas produce more localized changes in the bones than fibrous dysplasia.

Question 9

This infant was born with an anomaly of the left lower extremity (Slides). What is the most likely diagnosis:

Explanation

This infant has tibial hemimelia, which is a complete absence of the tibia with resultant inversion of the foot. The presence of an intact fibula causing focal lateral prominence, a shortened but complete femur, and absence of a visible tibia rule out a diagnosis of clubfoot, proximal focal femoral deficiency, fibular hemimelia, and congenital pseudarthrosis of the tibia.

Question 10

This child with tibial hemimelia does not have a proximal tibial remnant (Slides). The preferred treatment is:

Explanation

If the proximal tibial remnant is absent, the prospect of a functionally useful extension at the knee is nil. Disarticulation at the knee is the best option for this patient.

Question 11

Which of the following Risser signs most accurately describes the patient presented (Slide):

Explanation

Despite its biologic variability, the Risser sign is one of the most useful indicators of maturity used in the management of pediatric spine disorders. The Risser sign is a depiction of the progressive ossification and fusion of the iliac apophysis, which begins anterolaterally and finishes posteromedially. The initial ossification (Risser 1) begins just after the peak height velocity, after triradiate cartilage closure, and approximately at the time of menarche. The completion of ossification and fusion usually takes 1½ to 2 years in girls and 2 to 3 years in boys. As the iliac apophysis matures and Risser 4 is reached, the Risser sign becomes a sclerotic line that is whiterâ than the adjacent ilium. Risser 0 and Risser 5 may be difficult to Orthopedic Prometric Exam Chapter 3 Image

Orthopedic Prometric Exam Chapter 3 Image

distinguish except that the cranial border of the ilium in Risser 0 is wavy or ruffled, while it is smooth and sclerotic in Risser 5.

Question 12

A 15-year-old boy presents with a spinal curvature and no other known disorders (Slide). His curve is 105° and corrects to 70° with traction. His neurologic examination is normal. The best treatment method would be:

Explanation

A large, rigid curve like this requires an anterior release and fusion to obtain flexibility. The anterior release should be followed by a posterior fusion with instrumentation either on the same day or after a period of traction. Anterior instrumentation alone increases the risk of cut out and incomplete correction. Orthopedic Prometric Exam Chapter 3 Image

Question 13

Numerous braces are available for controlling spinal deformities in growing children. Which type of brace is presented here (pic):

Explanation

The Milwaukee brace is the first modern scoliosis brace to demonstrate efficacy and to achieve widespread use. The Milwaukee brace is a cervicothoracolumbar orthosis. All of the other braces listed are thoracolumbosacral orthoses. Orthopedic Prometric Exam Chapter 3 Image

The Boston brace is prefabricated and is selected from measurements taken of the patient. The C harleston brace is a night-only brace and bends the patient to reverse the curve. The Wilmington brace is made of thermoplastic material for rapid, on-site fabrication. The Providence brace is made using computer-assisted machining to help achieve maximal correction.

Question 14

A patient has idiopathic scoliosis measuring 62° thoracic convex to the right and 40° lumbar convex to the left (Slide). The sagittal film shows a relatively decreased thoracic kyphosis and decreased lumbar lordosis. The patient is 13 years old and is 2 months postmenarchal. Which of the following treatments is most appropriate:

Orthopedic Prometric Exam Chapter 3 Image

Explanation

This curve may be classified as a King type II or III. The curve is too large for bracing. Only the thoracic curve must be fused. Because the stable vertebra is L2, the fusion does not need to go below this level. Other acceptable options include anterior thoracic instrumentation and fusion from T4 to T12 or posterior instrumented fusion to L1.

Question 15

Which of the following terms best describes the condition shown (Slide):

Explanation

This patientâ s foot is in calcaneovalgus. Treatment is not required because calcaneovalgus spontaneously resolves.

Question 16

A 4-year-old boy is brought to the doctor for evaluation of his feet. His mother is concerned that he has no arch. He does not have any pain in his feet, and there are no calluses on the plantar surface. Radiographs of one of the feet are shown below. You recommend:

Orthopedic Prometric Exam Chapter 3 Image

Explanation

The radiographs demonstrate a normal appearance of a foot in a young child. The angle between the talus and calcaneus is increased at this age. The arch in a young child is not as well developed as in an older child. The navicular has not ossified yet. No treatment is needed.

Question 17

A 13-year-old girl is brought to the office for evaluation of her feet. During gait, she has a foot progression angle of 45° outward on each side. Her transmalleolar axis is 20° outward on each side. Her hips have internal rotation in extension of 40° and external rotation in extension of 40°. Her clinically estimated anteversion is 20°. She has popliteal angles of 20° bilaterally and full knee extension during swing. Standing radiographs of the feet are presented. Which factor is most likely to be the cause of her toeing- out:

Explanation

This patient has significant forefoot abduction demonstrated on the standing foot radiographs. The femoral anteversion of 20° is within normal limits for age. The transmalleolar and popliteal angles are also within normal limits. There is no evidence of dynamic knee torsion as a factor in alignment of children.

Question 18

After being dragged by an automobile, a 7-year-old child sustained injuries to his foot (Slide). Following reconstructive surgery, he is most likely to be left with a permanent deficit in which of the following:

Orthopedic Prometric Exam Chapter 3 Image

Explanation

This patient sustained a dorsal degloving injury. The anterior tibialis tendon is gone, as are some of the toe dorsiflexors. The anterior tibial function is difficult to reconstruct, even after tendon transfer, because of scarring at the insertion site.

Question 19

What best describes the anomalies depicted (Slide):

Explanation

The Slide shows two congenital hemivertebrae on the convex side plus a bar on the right side. An incarcerated hemivertebra fits into indentations in the adjacent vertebrae, causing no net deformity. A block vertebra is a pair of fully fused vertebrae usually without significant deformity.

Question 20

Compared to viral vectors, the advantages of non-viral vectors for gene delivery include all of the following except:

Explanation

Due to safety concerns, immunogenicity, and production issues associated with viral vectors, non-viral delivery systems were developed by complexing of genes (DNA) to various chemical formulations. This makes the DNA stable and increases its uptake. They include plasmids, peptides, cationic liposomes, DNA-ligand complexes (recognize specific cell-surface receptors, leading to receptor- mediated uptake), and gene gun (particles of gold coated with DNA, forced into the cells with high velocity bombardment). However, their efficiency is lower than viral vectors.

Question 21

Which of the following fracture patterns carries the highest specificity for non-accidental trauma (child abuse) in an infant?

Explanation

Posterior rib fractures, metaphyseal corner (bucket-handle) fractures, and scapular or spinous process fractures have the highest specificity for non-accidental trauma in infants.

Question 22

A 6-year-old child presents with back pain. Radiographs reveal a 'vertebra plana' deformity.

Biopsy of the lesion is most likely to demonstrate which of the following histological features?

Explanation

The clinical presentation of vertebra plana in a child is highly characteristic of Langerhans cell histiocytosis (eosinophilic granuloma). Histology shows Langerhans cells with coffee-bean nuclei, Birbeck granules on electron microscopy, and positive CD1a/S-100 staining.

Question 23

A 9-month-old non-ambulatory infant presents with a spiral fracture of the femoral shaft. What is the most appropriate next step in management?

Explanation

Spiral femur fractures in non-ambulatory infants are highly suspicious for non-accidental trauma. A skeletal survey and child protective services consultation are mandatory.

Question 24

A 12-year-old boy presents with night pain in his proximal tibia that is relieved by NSAIDs. Radiographs show a sclerotic lesion with a 1 cm radiolucent nidus. What is the most likely diagnosis?

Explanation

Night pain relieved by NSAIDs and a radiolucent nidus <1.5 cm surrounded by reactive sclerosis are pathognomonic for osteoid osteoma.

Question 25

A 10-year-old asymptomatic girl is incidentally found to have a 2 cm eccentrically located, sharply demarcated radiolucent lesion with a sclerotic margin in the distal femoral metaphysis. What is the most appropriate management?

Explanation

Nonossifying fibromas (NOF) are common benign, asymptomatic lesions that typically regress spontaneously. Observation is the standard of care for small, asymptomatic lesions.

Question 26

A 13-year-old obese boy presents with right knee pain and an obligate external rotation of the hip during passive flexion. Radiographs show a "trellis" sign and Klein's line not intersecting the lateral epiphysis. What is the most appropriate initial treatment?

Explanation

The clinical presentation and radiographic findings are classic for Slipped Capital Femoral Epiphysis (SCFE). The standard initial treatment is in situ fixation with a single cannulated screw.

Question 27

A 9-year-old boy presents with a pathologic fracture of the proximal humerus after a minor fall. Radiographs reveal a centrally located lytic lesion extending to the physis with a "fallen leaf" sign. What is the best initial management for the cyst?

Explanation

A "fallen leaf" sign indicates a Unicameral Bone Cyst. Initial management of a pathologic fracture through a UBC is observation, as the fracture may induce spontaneous cyst healing.

Question 28

An 11-year-old girl presents with a rapidly expanding, painful lesion in her distal tibia. Biopsy reveals blood-filled spaces separated by septa lacking endothelial lining. Which genetic translocation is most commonly associated with this primary lesion?

Explanation

Aneurysmal bone cysts (ABCs) are characterized by blood-filled cystic spaces and are primarily associated with USP6 gene rearrangements on chromosome 17p13.

Question 29

In a 7-year-old boy diagnosed with Legg-Calve-Perthes disease, which of the following radiographic findings represents a "head at risk" sign indicating a poorer prognosis?

Explanation

Catterall's "head at risk" signs include lateral subluxation, Gage sign (V-shaped defect in the lateral epiphysis), calcification lateral to the epiphysis, and horizontal growth plate.

Question 30

A 6-year-old boy sustains an extension-type supracondylar humerus fracture. He is unable to flex the interphalangeal joint of his thumb. Which nerve is most likely injured?

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the FPL, responsible for thumb IP joint flexion.

Question 31

A 15-year-old boy presents with a painful mass in the distal femur. Radiographs reveal a sunburst periosteal reaction and Codman's triangle. Which of the following is the most significant prognostic factor for survival?

Explanation

The percentage of tumor necrosis following neoadjuvant chemotherapy is the most critical prognostic indicator for long-term survival in osteosarcoma.

Question 32

A 9-year-old boy presents with fever, elevated ESR, and a diaphyseal lytic lesion in the femur with an "onion-skin" periosteal reaction. Histology shows small blue round cells. What is the pathognomonic chromosomal translocation?

Explanation

Ewing sarcoma is characterized by the t(11;22)(q24;q12) translocation, resulting in the EWS-FLI1 fusion protein. It often mimics osteomyelitis clinically.

Question 33

A 4-week-old female infant has a positive Ortolani test on the left side. Ultrasound shows an alpha angle of 40 degrees. What is the most appropriate next step in management?

Explanation

A positive Ortolani test with an alpha angle < 60 degrees indicates a dislocated but reducible hip. The Pavlik harness is the gold standard initial treatment for DDH in infants under 6 months.

Question 34

A 14-year-old boy complains of chronic knee pain. Radiographs reveal a 2 cm eccentric, radiolucent lesion in the proximal tibial epiphysis with a thin sclerotic rim. Histology shows "chicken-wire" calcification. What is the diagnosis?

Explanation

Chondroblastoma is a benign cartilage-forming tumor that characteristically arises in the epiphysis of long bones in growing children. "Chicken-wire" calcification is a classic histologic hallmark.

Question 35

A 5-year-old boy presents with multiple fractures, blue sclerae, and hearing loss. A defect in which of the following is the primary cause of his condition?

Explanation

Osteogenesis imperfecta is primarily caused by mutations in the COL1A1 or COL1A2 genes, which encode the chains of Type I collagen.

Question 36

When evaluating a child for suspected non-accidental trauma, which of the following laboratory profiles best differentiates severe nutritional rickets from osteogenesis imperfecta (OI)?

Explanation

While both conditions can cause pediatric fractures, OI is caused by abnormal type I collagen. Rickets typically presents with elevated PTH and Alk Phos, along with low/normal calcium and low Vitamin D.

Question 37

A 6-year-old girl sustains a displaced lateral condyle fracture of the humerus. Which of the following is the most common complication if this fracture is left untreated or goes on to nonunion?

Explanation

Nonunion of a lateral condyle fracture typically leads to a progressive cubitus valgus deformity. This chronic stretching can lead to a tardy ulnar nerve palsy.

Question 38

A 3-year-old boy presents with progressive bilateral genu varum. Radiographs show a sharp varus angulation at the proximal tibial metaphysis with medial beaking. What is the most likely diagnosis?

Explanation

Infantile Blount's disease involves a growth disturbance of the medial aspect of the proximal tibial physis. Radiographically, it is characterized by medial metaphyseal beaking and fragmentation.

Question 39

According to the Delbet classification, which type of pediatric proximal femur fracture carries the highest risk of avascular necrosis (AVN)?

Explanation

Delbet Type I (transepiphyseal) fractures are rare but carry the highest risk of AVN. The AVN rate approaches nearly 100% in completely displaced cases.

Question 40

A 13-year-old boy sustains a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis. What is the primary deforming force causing this specific fracture pattern?

Explanation

A juvenile Tillaux fracture is an SH III fracture of the anterolateral distal tibial epiphysis. It is caused by an avulsion force from the AITFL during external rotation, occurring because the medial physis closes before the lateral physis.

Question 41

During the Ponseti casting technique for idiopathic clubfoot, what is the final deformity corrected before considering an Achilles tenotomy?

Explanation

The Ponseti method corrects deformities in the order of CAVE: Cavus, Adductus, Varus, and finally Equinus. An Achilles tenotomy is frequently required to correct the residual equinus.

Question 42

A 14-year-old gymnast presents with persistent low back pain. Radiographs demonstrate a grade II isthmic spondylolisthesis at L5-S1. What is the underlying anatomic defect?

Explanation

Isthmic spondylolisthesis (Type II) is caused by a defect or stress fracture in the pars interarticularis. It is commonly seen in young athletes like gymnasts due to repetitive hyperextension.

Question 43

A 4-year-old boy presents with right hip pain, refusing to bear weight. His temperature is 38.6°C, ESR is 45 mm/hr, and WBC is 10,500/mm³. Radiographs are unremarkable. According to the Kocher criteria, what is the approximate probability that this child has septic arthritis?

Explanation

The Kocher criteria for septic arthritis of the hip include non-weight-bearing, temperature >38.5°C, ESR >40 mm/hr, and WBC >12,000/mm³. This patient meets three criteria, which corresponds to a 93% predicted probability of septic arthritis.

Question 44

A 4-month-old female is treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her follow-up appointment, the parents report she is not kicking her right leg as much as the left. Which of the following nerve palsies is the most common complication of excessive hip flexion in a Pavlik harness?

Explanation

Femoral nerve palsy is the most common nerve injury associated with the Pavlik harness, typically caused by excessive hip flexion. Excessive abduction, conversely, increases the risk of avascular necrosis of the femoral head.

Question 45

A pediatric orthopedic surgeon is utilizing the Ponseti method to correct an infant's idiopathic clubfoot. What is the correct sequential order of deformity correction in this technique?

Explanation

The Ponseti method corrects clubfoot deformities in a specific sequence represented by the mnemonic CAVE: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by elevating the first ray.

Question 46

A 13-year-old obese male presents with left knee pain and a limp. Examination reveals obligate external rotation of the hip with passive flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following best describes the anatomical displacement of the femoral neck relative to the epiphysis?

Explanation

In SCFE, the epiphysis remains seated within the acetabulum while the femoral neck displaces anteriorly and superiorly. Radiographically, the epiphysis appears to have slipped posteriorly and inferiorly.

Question 47

A 6-year-old girl falls from monkey bars and sustains a widely displaced posterolateral extension-type supracondylar humerus fracture. Which nerve is most at risk in this specific displacement pattern?

Explanation

In a posterolateral supracondylar fracture, the proximal fragment is driven anteromedially, putting the median nerve and its anterior interosseous branch (AIN) at highest risk. Posteromedial displacement places the radial nerve at risk.

Question 48

A 14-year-old boy presents with frequent ankle sprains and a rigid, painful flatfoot. Lateral radiographs demonstrate a distinct "C sign". Which of the following is the most appropriate imaging modality to best characterize the anatomical extent of this suspected pathology?

Explanation

The "C sign" is indicative of a talocalcaneal tarsal coalition. A CT scan of the foot and ankle is the gold standard imaging modality to characterize the location, extent, and osseous nature of tarsal coalitions.

Question 49

During the progression of Legg-Calvé-Perthes disease, which radiographic sign represents a subchondral fracture and typically heralds the onset of the fragmentation stage?

Explanation

The crescent sign represents a subchondral fracture of the femoral head. It usually indicates the transition from the initial avascular necrosis phase to the fragmentation stage in Legg-Calvé-Perthes disease.

Question 50

An 8-year-old boy presents with sudden arm pain after throwing a baseball. Radiographs demonstrate a centrally located, lucent metaphyseal lesion in the proximal humerus with a "fallen leaf" sign.

Following fracture healing, what is the most appropriate initial management for this active lesion?

Explanation

The "fallen leaf" sign is pathognomonic for a unicameral (simple) bone cyst. After the pathological fracture has healed, active cysts with a high risk of re-fracture are typically treated first-line with aspiration and intralesional corticosteroid or bone marrow injection.

Question 51

A 2-year-old girl is evaluated for multiple low-energy fractures. Clinical examination reveals blue sclerae and opalescent, abnormally wearing teeth (dentinogenesis imperfecta). A mutation in which of the following genes is most likely responsible for her condition?

Explanation

Osteogenesis imperfecta is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode for type I collagen. This leads to bone fragility, blue sclerae, and dentinogenesis imperfecta.

Question 52

A 3-year-old boy presents with progressive bowing of his left leg. Radiographs reveal a depressed medial tibial metaphysis with a beaked appearance, consistent with Langenskiöld stage III infantile Blount's disease. What is the most appropriate surgical treatment?

Explanation

For a child aged 3 or older with Langenskiöld stage III or higher infantile Blount's disease, proximal tibial valgus osteotomy is the standard of care to correct the severe mechanical axis deviation and relieve pressure on the medial physis.

Question 53

A 13-year-old boy sustains a twisting injury to his ankle. CT scan reveals a classic triplane fracture. In which planes do the fracture lines of a classic triplane fracture occur?

Explanation

A triplane fracture typically occurs in adolescents during asymmetric physeal closure. The fracture lines propagate in the coronal plane through the metaphysis, transverse plane through the physis, and sagittal plane through the epiphysis.

Question 54

A 14-year-old girl presents with an isolated juvenile Tillaux fracture of the distal tibia. Which of the following describes the mechanism of injury and the deforming anatomical structure?

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It is caused by an external rotation force where the anterior inferior tibiofibular ligament (AITFL) avulses the bony fragment.

Question 55

A 7-year-old child with spastic quadriplegic cerebral palsy presents for routine hip surveillance. AP pelvis radiographs reveal a migration percentage of 45% in the right hip. Which of the following is the most appropriate management?

Explanation

In children with cerebral palsy, a hip migration percentage >40% typically indicates a progressive subluxation that will not resolve with soft tissue releases alone. Bony reconstruction with a VDRO, often combined with a pelvic osteotomy, is required.

Question 56

A newborn is evaluated for bilateral "rocker-bottom" foot deformities. Radiographs with forced plantar flexion show that the navicular remains dorsally dislocated on the talar neck. What is the fundamental pathology of this condition?

Explanation

The clinical presentation and radiographic failure of the navicular to reduce with forced plantarflexion defines congenital vertical talus. Its hallmark is a rigid dorsal dislocation of the navicular on the head/neck of the talus.

Question 57

Which of the following radiographic fracture patterns is considered to have the highest specificity for non-accidental trauma in an infant?

Explanation

Metaphyseal corner fractures, or "bucket-handle" fractures, are highly specific for child abuse, resulting from rapid rotational or shearing forces applied to a child's limb. While spiral femur fractures are concerning in non-ambulatory infants, metaphyseal lesions carry the highest specificity.

Question 58

A 9-year-old boy sustains a pathologic fracture through a centrally located, expansile radiolucent lesion in the proximal humerus. Radiographs show a "fallen leaf" sign. After the fracture has healed, the lesion remains active and expansive. What is the most appropriate initial minimally invasive management?

Explanation

The "fallen leaf" sign is pathognomonic for a unicameral bone cyst (UBC). After allowing the fracture to heal, active UBCs are typically treated initially with aspiration and intralesional injection of corticosteroids or bone marrow aspirate.

Question 59

A 2-year-old child presents with a history of recurrent fractures following minimal trauma, blue sclerae, and early hearing loss. This presentation is primarily due to a genetic defect in the synthesis of which of the following?

Explanation

Osteogenesis imperfecta is characterized by bone fragility, blue sclerae, and dentinogenesis imperfecta. It is caused by mutations in the COL1A1 or COL1A2 genes, which lead to qualitative or quantitative defects in Type I collagen.

Question 60

A 10-year-old girl is evaluated for a limp. Radiographs demonstrate a "shepherd's crook" deformity of the proximal femur with a ground-glass appearance of the medullary canal. She also exhibits precocious puberty and irregular café-au-lait spots. What is the most likely diagnosis?

Explanation

McCune-Albright syndrome is a triad of polyostotic fibrous dysplasia (causing the ground-glass bone lesions and shepherd's crook deformity), café-au-lait spots with irregular "coast of Maine" borders, and endocrinopathies such as precocious puberty.

Question 61

A 6-year-old boy sustains a completely displaced extension-type supracondylar fracture of the humerus. During the neurological exam, he is unable to flex the interphalangeal joint of his thumb or the distal interphalangeal joint of his index finger. Which nerve has most likely been injured?

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures. Injury to the AIN results in the inability to flex the IP joint of the thumb and the DIP joint of the index finger (the "A-OK" sign).

Question 62

An 11-year-old boy presents with localized thigh pain and a low-grade fever. Radiographs reveal a permeative, destructive diaphyseal lesion in the femur with a multilamellated ("onion skin") periosteal reaction. Biopsy shows sheets of small, round, blue cells. Which chromosomal translocation is characteristically associated with this tumor?

Explanation

The clinical and radiographic presentation is classic for Ewing sarcoma. The t(11;22) translocation is found in approximately 85% of Ewing sarcoma cases, leading to the creation of the EWS-FLI1 fusion protein.

Question 63

In a child diagnosed with Legg-Calvé-Perthes disease, which of the following factors has been shown to be the most significant prognostic indicator for the long-term anatomic outcome of the hip?

Explanation

Age at the onset of Legg-Calvé-Perthes disease is the most critical prognostic factor. Children who develop the disease before 6 to 8 years of age have a significantly better prognosis due to the greater remaining growth potential for femoral head remodeling.

Question 64

A 13-year-old obese boy presents with acute knee pain and inability to bear weight. Radiographs show a severe acute-on-chronic slipped capital femoral epiphysis (SCFE). Which of the following is the most devastating potential complication of forceful anatomic reduction of the slip prior to fixation?

Explanation

Forceful reduction of a displaced SCFE significantly stretches or tears the delicate epiphyseal blood supply (retinacular vessels), dramatically increasing the risk of avascular necrosis (AVN). In situ pinning is generally preferred to minimize this risk.

Question 65

A 14-month-old child presents with severe bowing of the legs. Radiographs show widened physes and "cupping and fraying" of the metaphyses. Laboratory evaluation reveals hypophosphatemia, normal serum calcium, and normal parathyroid hormone levels. What is the most likely diagnosis?

Explanation

X-linked hypophosphatemic rickets is caused by a defect in renal phosphate reabsorption (PHEX gene mutation), leading to isolated hypophosphatemia. Unlike nutritional rickets, calcium and PTH levels typically remain within normal limits.

Question 66

A 10-month-old infant presents with extreme irritability, bleeding gums, and pseudoparalysis of the lower extremities. Radiographs of the knees show a dense zone of provisional calcification (Frankel line) and a radiolucent band directly beneath it (Trümmerfeld zone). Which of the following dietary deficiencies is responsible?

Explanation

Vitamin C deficiency (scurvy) impairs collagen hydroxylation, leading to capillary fragility and subperiosteal hemorrhages (causing extreme pain and pseudoparalysis). Radiographic hallmarks include the Frankel line, Trümmerfeld zone, and Wimberger ring sign.

Question 67

A 2-year-old girl refuses to bear weight on her right leg after tripping over a toy. Initial radiographs of the tibia and fibula are interpreted as normal. A bone scan demonstrates diffusely increased uptake in the distal third of the right tibia. What is the most likely diagnosis?

Explanation

A toddler's fracture is a subtle, nondisplaced spiral fracture of the distal tibia common in children aged 9 months to 3 years. Initial radiographs may appear normal, and treatment consists of simple immobilization.

Question 68

A 5-year-old boy sustains a lateral condyle fracture of the humerus. Which of the following long-term complications is most frequently associated with nonunion of this specific fracture pattern due to inadequate initial treatment?

Explanation

Lateral condyle fractures are intra-articular and highly prone to nonunion if displaced due to the pull of the extensor muscles and synovial fluid bathing the fracture. Nonunion typically leads to a progressive cubitus valgus deformity, which can subsequently cause tardy ulnar nerve palsy.

Question 69

A 14-year-old boy presents with an ankle injury. Radiographs reveal a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis (Tillaux fracture). What is the primary anatomical basis for this specific injury pattern in adolescents?

Explanation

The distal tibial physis closes asymmetrically, starting centrally, then moving medially, and finally laterally. In adolescence, the lateral portion remains open and vulnerable to avulsion by the anterior inferior tibiofibular ligament (AITFL), causing a Tillaux fracture.

Question 70

A 2-year-old boy is diagnosed with congenital pseudarthrosis of the tibia (CPT). This condition is most strongly associated with which of the following systemic disorders?

Explanation

Congenital pseudarthrosis of the tibia is highly associated with Neurofibromatosis type 1 (NF-1). Approximately 50% of patients with CPT have NF-1, characterized by anterolateral bowing of the tibia that progresses to pseudarthrosis.

Question 71

A 14-year-old female gymnast complains of insidious onset low back pain that worsens with back extension. Oblique radiographs of the lumbar spine reveal a "Scotty dog with a collar" sign. What is the most appropriate initial management?

Explanation

The "Scotty dog with a collar" sign indicates a pars interarticularis defect (spondylolysis). Initial management in a young athlete is conservative, focusing on rest, activity modification, and physical therapy focused on core and hamstring strengthening.

Question 72

A 4-year-old obese girl presents with severe, progressive bilateral genu varum. Radiographs show marked depression of the medial tibial plateau and a prominent medial metaphyseal beak. Given her age and progressive deformity (Langenskiöld stage III), what is the most appropriate surgical intervention?

Explanation

Infantile Blount disease in children older than 3 years with severe or progressive deformity (Langenskiöld stage III or higher) generally requires surgical correction. A proximal tibial valgus osteotomy is the gold standard to restore normal mechanical axis and relieve pressure on the medial physis.

Orthopedic Prometric MCQs - Chapter 3 Part 1

Orthopedic Prometric MCQs - Chapter 3 Part 8

Orthopedic Prometric MCQs - Chapter 3 Part 8

Chapter Index