Question 1

Which of the following physical findings is uncommon in a patient with a unilateral untreated clubfoot:

Explanation

In a patient with unilateral untreated clubfoot, certain findings are apparent when compared with the unaffected foot. Common findings include a thinner calf, shorter-appearing foot, loss of heel prominence, and a medial midfoot crease. The talus is prominent anterolaterally in the foot but not on the plantar-medial side.

Question 2

Which of the following radiographic findings is present in a varus foot:

Explanation

Plain radiographs of a foot that is in varus show increased parallelism of the talus and the calcaneus on both the anteroposterior and lateral films. There is decreased superimposition of the talus, the calcaneus, and the metatarsal heads. By contrast, in a valgus foot, there is increased divergence on both the anteroposterior and lateral films.

Question 3

Although all of the following conditions may present in patients with skeletal dysplasia, which is the only condition that does not have a high frequency of spontaneous improvement:

Explanation

Cervical kyphosis does not improve in patients with Larsen syndrome and may cause myelopathy. Early arthrodesis (posterior only, if not too severe) is indicated. All of the other conditions have a high incidence of spontaneous improvement, so they are most appropriately treated with observation. In a minority of cases, the deformity does not improve and surgery is indicated.

Question 4

All of the following conditions may affect lower extremities in children. Which one of the conditions does not have a high incidence of spontaneous improvement:

Explanation

Anterolateral bowing of the tibia is usually associated with tibial dysplasia and may progress to pseudarthrosis. Anterolateral bowing of the tibia does not resolve in most patients. Posteromedial bowing of the tibia usually resolves, although there may be a residual shortening of the tibia. All of the other conditions often completely resolve.

Question 5

The anterior interosseous nerve enables:

Explanation

The anterior interosseous nerve does not carry any sensory fibers. The anterior interosseous nerve enables flexion of the thumb (flexor digitorum pollicis) and index fingers (flexor digitorum profundus). This is the most commonly injured nerve in a supracondylar fracture, and it nearly always spontaneously recovers.

Question 6

Closed reduction without internal fixation is most likely to produce a satisfactory result in which of the following types of supracondylar fracture:

Explanation

There are many options when treating a supracondylar fracture, but a surgeon should always choose the method with the highest percentage of good results for a given fracture. Answer A describes a type II supracondylar fracture with hyperextension and no varus-valgus displacement. The posterior hinge is intact, and it is relatively simple to reduce the fracture with flexion, immobilizing it at 120°. For the other fractures listed as possible answer choices, the reduction as well as the assessment of reduction is more complex. Therefore, most experts would prefer percutaneous fixation of these fractures once reduced.

Question 7

The highest rate of success in restoring growth after physeal bar resection is found in which location:

Explanation

The highest rate of success after physeal bar resection is found in the distal tibia. The mean growth after resection in the series by Peterson was 93% of that expected, which is greater than the success rates of the other locations. The reasons for this remain speculative but may be due to the more peripheral location of the bar at the ankle, less complex physeal shape, and lower energy of injury. Physeal bars in the proximal femur and humerus are rarely surgically treated.

Question 8

Which of the following fracture types are most prone to nonunion or refracture in patients with osteogenesis imperfecta:

Explanation

Unless they are internally fixed, olecranon fractures are notoriously prone to nonunion or refracture in patients with osteogenesis imperfecta. The remaining fractures can be treated nonoperatively with cast immobilization.

Question 9

An 11-year-old boy has multiple, hard, tender nodules in his posterior shoulder girdle and paraspinous muscles. He also has a shortened first metatarsal with a delta-shaped first proximal phalanx. The diagnosis is:

Explanation

Fibrodysplasia ossificans progressiva is a disorder of the BMP4 signaling pathway. This condition is characterized by multiple osseous masses occurring in muscle, especially in the dorsal and axial regions. There is also a characteristic dysmorphology of the great toe, consisting of a shortened first metatarsal, delta-shaped phalanx, and some valgus.

Question 10

Klippel-Trenaunay syndrome is characterized by cutaneous capillary venous malformation, varicose veins, and which of the following:

Explanation

Klippel-Trenaunay syndrome has three essential features: cutaneous capillary venous malformation, varicose veins, and hypertrophy of the involved limb in length and/or width. The syndrome usually presents before adolescence. The tissue abnormalities typically do not cross the midline, and the entire limb is not uniformly affected.

Question 11

Which of the following characterizes Russell-Silver syndrome:

Explanation

Russell-Silver syndrome is characterized by a small triangular face, hemiatrophy of up to 5 cm, delay in skeletal age, and sometimes a developmental delay. Scoliosis is commonly found in patients with Russell- Silver syndrome.

Question 12

Macrodactyly is associated with all of the following syndromes except:

Explanation

Macrodactyly is an increase in length and width of a digit or two adjacent digits. It may be associated with all of the above syndromes except for Marfan syndrome. Macrodactyly is also a common isolated condition.

Question 13

Which of the following conditions is inherited in an X-linked dominant fashion:

Explanation

Familial hypophosphatemic rickets is inherited in an X-linked dominant fashion, meaning that there is an excess of affected females. Hemophilia A is sex-linked recessive like most X-linked conditions (seen primarily in males). Marfan syndrome is autosomal dominant, sickle cell anemia is autosomal recessive, and Prader-Willi syndrome is a partial deletion of chromosome 15.

Question 14

Which of the following statements is true regarding congenital pseudarthrosis of the tibia:

Explanation

Congenital pseudarthrosis of the tibia is associated with neurofibromatosis in approximately one-half of patients. It usually occurs in the distal portion of the tibia, presents with a varus position, and an apex-anterior bow. The surrounding bone is usually dysplastic, displaying segments of sclerosis, tapering, and/or cystic changes. The fibula is often dysplastic as well.

Question 15

Which of the following elements is most critical to the success of the Williams rod procedure (intramedullary rod fixation) for congenital pseudarthrosis of the tibia:

Explanation

Fixation of the fibula allows shortening and compression of the tibia, as well as providing mechanical stability. Neither leaving the rod across the ankle nor prolonged orthotic protection beyond the initial postoperative period appears to be essential. Electrical stimulation does not have a quantifiable effect on the success of the procedure. Ultrasound has not been studied in this condition.

Question 16

Which of the following is considered the cutoff for normal loss of C 1-C 2 articular contact in dynamic computed tomography (C T) in normal patients:

Explanation

Up to 80% loss of contact between the C 1 and C 2 facet joints may be seen in normal patients. Therefore, dynamic C T is an oversensitive test and the dynamic feature does not add to C T in diagnosis.

Question 17

In the absence of surgery, which of the following gait parameters in children with cerebral palsy tends to remain static with increasing age:

Explanation

Most parameters of gait deteriorate over time in the absence of intervention in children with cerebral palsy. Knee and ankle range of motion decrease, as does walking velocity when normalized for height. Femoral anteversion remains unchanged. Knee stiffness increases.

Question 18

In patients with cerebral palsy, which of the following factors usually leads to an improvement in walking ability:

Explanation

Gait in patients with cerebral palsy declines with increases in age, body mass index, external tibial torsion, and significant ankle valgus (due to worsened mechanics of pushoff). Gait is improved by aligning the foot rocker with the line of progression.

Question 19

Nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) have the following effect on spinal fusion:

Explanation

Nonselective NSAIDs have been shown to decrease fusion rates in both animal models and in humans. The mechanism is most likely through an inhibition of cyclooxygenase (C OX)-1 because C OX-2 inhibitors do not show this effect.

Question 20

The upper-end vertebra for measurement of kyphosis should always be:

Explanation

As in measurement of any spinal curve, the upper-end reference is the most inclined upper vertebra. One should carefully select this level and ensure that comparison measurements utilize the same vertebral levels.

Question 21

During the initial phase of the Ponseti method for idiopathic clubfoot, which component of the deformity is corrected first?

Explanation

The sequence of correction in the Ponseti method follows the acronym CAVE: Cavus, Adductus, Varus, and Equinus. Cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot.

Question 22

What is the most common cause of relapse in an infant successfully treated for idiopathic clubfoot with the Ponseti method?

Explanation

Noncompliance with the foot abduction orthosis (Denis Browne splint) is universally recognized as the most common cause of relapse following successful initial casting correction.

Question 23

During clubfoot treatment using the Ponseti technique, what is the primary indication for performing a percutaneous Achilles tenotomy?

Explanation

An Achilles tenotomy is indicated before the final cast when the midfoot is fully corrected (adductus, varus, and cavus are resolved) but residual equinus prevents 10 to 15 degrees of ankle dorsiflexion.

Question 24

Which radiographic finding on a lateral foot view is pathognomonic for congenital vertical talus?

Explanation

Congenital vertical talus is characterized by a rigid, irreducible dorsal dislocation of the navicular on the head of the talus. A forced plantarflexion lateral radiograph confirms the inability to reduce the talonavicular joint.

Question 25

Congenital vertical talus is most frequently associated with which of the following underlying conditions?

Explanation

More than 50% of congenital vertical talus cases are associated with neuromuscular or genetic syndromes. Arthrogryposis multiplex congenita and myelomeningocele are the most common associated conditions.

Question 26

A 14-year-old boy presents with painful, rigid flatfeet and recurrent ankle sprains. A "C sign" is distinctly visible on his lateral foot radiograph. What is the most likely diagnosis?

Explanation

The C sign on a lateral foot radiograph represents a continuous bony bridge between the talar dome and the sustentaculum tali, strongly indicating a talocalcaneal coalition.

Question 27

Which specific radiographic view is most sensitive for diagnosing a calcaneonavicular coalition?

Explanation

The 45-degree internal oblique radiograph of the foot is the best plain film view to visualize the anterior process of the calcaneus and the navicular, making it the most sensitive view for identifying a calcaneonavicular coalition.

Question 28

Which of the following correctly pairs the genetic mutation and inheritance pattern of achondroplasia?

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene. It is inherited in an autosomal dominant pattern, although 80% of cases are due to de novo mutations.

Question 29

What is the most common symptomatic spinal complication requiring surgical decompression in adult patients with achondroplasia?

Explanation

Spinal stenosis is the most common spinal complication in adult achondroplastic patients. It results from short pedicles, a narrowed interpedicular distance, and thickened ligamentum flavum.

Question 30

Which clinical feature distinguishes pseudoachondroplasia from achondroplasia?

Explanation

Unlike achondroplasia, which is characterized by frontal bossing and midface hypoplasia, patients with pseudoachondroplasia have a completely normal facial appearance and normal head circumference.

Question 31

A 6-year-old child presents with short stature, early-onset joint pain, and a waddling gait. Radiographs demonstrate delayed and fragmented ossification of the epiphyses, but spinal radiographs are completely normal. What is the most likely diagnosis?

Explanation

Multiple epiphyseal dysplasia (MED) affects the epiphyses of long bones but classically spares the spine. This differentiates it from spondyloepiphyseal dysplasia (SED), which involves both the spine and the epiphyses.

Question 32

A newborn presents with severe, rigid clubfeet, "cauliflower" ear deformities, and "hitchhiker" thumbs. Which of the following is the underlying diagnosis?

Explanation

Diastrophic dysplasia is an autosomal recessive condition caused by an SLC26A2 sulfate transporter defect. Its clinical hallmarks include hitchhiker thumbs, cystic ear swelling (cauliflower ears), cleft palate, and very rigid clubfeet.

Question 33

What is the primary mechanism of action of intravenous bisphosphonates (e.g., pamidronate) used in treating children with osteogenesis imperfecta?

Explanation

Bisphosphonates act by disrupting osteoclast function and inducing osteoclast apoptosis. This inhibits bone resorption, increasing overall bone mineral density and reducing fracture rates in osteogenesis imperfecta.

Question 34

A patient with delayed closure of the fontanelles, multiple supernumerary teeth, and the ability to appose their shoulders anteriorly in the midline most likely has a mutation affecting which gene?

Explanation

The clinical picture is diagnostic for cleidocranial dysplasia. It is an autosomal dominant disorder caused by a mutation in the CBFA1 (RUNX2) transcription factor gene, which is essential for osteoblast differentiation.

Question 35

Which radiographic parameter is most predictive of progression in a 2-year-old child suspected of having infantile Blount disease rather than physiologic genu varum?

Explanation

A metaphyseal-diaphyseal angle (Drennan angle) of greater than 16 degrees is highly predictive for the progression of infantile Blount disease. Angles less than 10 degrees typically indicate physiologic bowing.

Question 36

A 4-year-old child presents with untreated Langenskiöld stage III infantile Blount disease. What is the most appropriate management?

Explanation

For a child older than 3 years or with a Langenskiöld stage III (or higher) deformity, bracing is largely ineffective. A proximal tibial valgus osteotomy is indicated to correct the mechanical axis and unweight the medial physis.

Question 37

In a patient with unilateral idiopathic clubfoot, the affected lower extremity typically demonstrates which of the following associated rotational profiles compared to the normal side?

Explanation

Idiopathic clubfoot is consistently associated with internal tibial torsion of the affected limb. This internal rotation typically persists even after the foot deformities have been fully corrected.

Question 38

A 12-year-old boy has bilateral cavovarus feet. A Coleman block test demonstrates a flexible hindfoot. In Charcot-Marie-Tooth disease, which primary muscle imbalance initiates the plantarflexed first ray?

Explanation

In Charcot-Marie-Tooth disease, the typical muscle imbalance driving the cavus deformity is a strong peroneus longus overpowering a weak tibialis anterior, which severely plantarflexes the first ray.

Question 39

A 3-month-old infant presents with flexible metatarsus adductus. Which of the following is the most appropriate initial management?

Explanation

The vast majority (over 90%) of flexible metatarsus adductus cases in infants resolve spontaneously without aggressive intervention. Observation with gentle stretching by the parents is the most appropriate initial treatment.

Question 40

Prior to administering general anesthesia for a patient with spondyloepiphyseal dysplasia congenita (SEDc), which cervical spine pathology must be specifically ruled out with flexion-extension radiographs?

Explanation

Patients with SEDc frequently have delayed ossification and hypoplasia of the odontoid process. This leads to profound atlantoaxial instability, posing a severe risk of cervical myelopathy or spinal cord injury during endotracheal intubation.

Question 41

A 2-year-old boy presents with a relapsed clubfoot deformity after successful initial treatment with the Ponseti method. What is the most common cause of recurrence, and what is the appropriate next step in management?

Explanation

Noncompliance with the abduction brace is the leading cause of clubfoot recurrence. The initial management of a relapsed clubfoot is a brief period of repeat Ponseti casting, which may be followed by a tendon transfer if dynamic supination persists.

Question 42

In a patient with an untreated congenital talipes equinovarus (clubfoot), what is the primary pathoanatomic deformity of the talus?

Explanation

In congenital clubfoot, the primary talar deformity is medial deviation and plantarflexion of the talar neck relative to the body. This structural change drives the subsequent medial subluxation of the navicular and calcaneus.

Question 43

A newborn presents with a rigid rocker-bottom foot deformity. Radiographs reveal a dorsally dislocated navicular on the talus. On a forced plantarflexion lateral view, the talonavicular joint fails to reduce. What is the most likely diagnosis?

Explanation

Congenital vertical talus is characterized by rigid dorsal dislocation of the navicular on the talus. The inability to reduce this alignment on a maximum plantarflexion lateral radiograph distinguishes it from a flexible oblique talus.

Question 44

An 11-year-old boy presents with a rigid flatfoot and recurrent ankle sprains. Radiographs show a "long nose" or "anteater" sign on the lateral view. Which of the following is the most appropriate next step to confirm the suspected diagnosis?

Explanation

The "anteater" sign is pathognomonic for a calcaneonavicular coalition. A 45-degree internal oblique radiograph of the foot is the best plain film view to directly visualize and confirm this specific condition.

Question 45

A 6-year-old child with a known FGFR3 gene mutation presents with progressive clumsiness and lower extremity hyperreflexia. Given the genetic diagnosis, what is the most likely cause of these neurological findings?

Explanation

Achondroplasia is caused by an FGFR3 mutation. In young children with this condition, cervicomedullary compression at the level of a stenotic foramen magnum is a critical complication presenting with hyperreflexia, clumsiness, or central apnea.

Question 46

A 9-year-old girl with Morquio syndrome (Mucopolysaccharidosis Type IV) presents for an orthopedic evaluation. Which of the following spinal conditions is the most life-threatening orthopedic complication associated with her diagnosis?

Explanation

Morquio syndrome is frequently complicated by severe odontoid hypoplasia and ligamentous laxity. This leads to profound atlantoaxial instability, which can cause life-threatening cervical myelopathy if unrecognized.

Question 47

Which of the following skeletal dysplasias is characterized by a mutation in the COMP (Cartilage Oligomeric Matrix Protein) gene, presenting with normal facies, short-limb dwarfism, and early-onset osteoarthritis?

Explanation

Pseudoachondroplasia is caused by mutations in the COMP gene. Patients typically have normal facial features but develop severe short-limb dwarfism, joint laxity, and early-onset osteoarthritis.

Question 48

A newborn is diagnosed with diastrophic dysplasia. Which of the following clinical features is classically associated with this condition?

Explanation

Diastrophic dysplasia is an autosomal recessive disorder caused by a defect in the SLC26A2 sulfate transporter gene. It is classically associated with short-limbed dwarfism, hitchhiker thumbs, cauliflower ears, and severe clubfeet.

Question 49

In a newborn with anterolateral bowing of the tibia, what is the most likely associated underlying diagnosis?

Explanation

Congenital anterolateral bowing of the tibia is strongly associated with Neurofibromatosis type 1. It often progresses to congenital pseudarthrosis of the tibia and requires specialized surgical management.

Question 50

A 1-month-old infant presents with posteromedial bowing of the tibia and a calcaneovalgus foot deformity. What is the expected natural history of this condition without surgical intervention?

Explanation

Congenital posteromedial bowing of the tibia generally improves spontaneously with remodeling as the child grows. However, patients typically develop a clinically significant leg length discrepancy requiring eventual equalization.

Question 51

During the Ponseti casting for a rigid clubfoot, which sequence correctly describes the order of deformity correction?

Explanation

The Ponseti method systematically corrects clubfoot deformities using the mnemonic CAVE: Cavus (by elevating the first ray), Adductus, Varus, and finally Equinus (often requiring a percutaneous Achilles tenotomy).

Question 52

A 4-year-old boy presents with bilateral flexible flatfeet. He has no pain, normal subtalar motion, and is able to perform a single-leg heel rise, during which the heel appropriately goes into varus. What is the most appropriate management?

Explanation

Flexible, asymptomatic flatfeet in a young child represent a normal physiologic variant. Treatment is not indicated, and the best management is reassurance to the parents, as arch development continues up to age 10.

Question 53

A 14-year-old male presents with deep posterior ankle pain during sports. Examination reveals decreased subtalar motion. Radiographs show a "C-sign" on the lateral view. Which anatomical structure is most commonly involved in this pathology?

Explanation

The "C-sign" on a lateral radiograph is indicative of a talocalcaneal coalition. The middle facet of the subtalar joint is the most common anatomical site for this type of bony or cartilaginous bridge.

Question 54

Spondyloepiphyseal dysplasia (SED) congenita is characterized by a primary defect in which of the following collagen types?

Explanation

SED congenita is caused by mutations in the COL2A1 gene, resulting in defective Type II collagen. This affects articular cartilage, the nucleus pulposus, and the vitreous humor of the eye.

Question 55

A 3-year-old child with infantile Blount's disease (tibia vara) presents with a Langenskiold stage III lesion. Which of the following is the most appropriate treatment to correct the deformity and prevent further progression?

Explanation

Langenskiold stage III infantile Blount's disease represents a progressive deformity with a "step-off" of the medial metaphysis. Surgical intervention with a proximal tibial valgus and derotation osteotomy is indicated to restore mechanical alignment.

Question 56

An infant is born with absent fibulae bilaterally. Which foot deformity is most classically associated with fibular hemimelia?

Explanation

Fibular hemimelia typically presents with shortening of the limb, anterior bowing of the tibia, and an equinovalgus foot deformity due to the absent lateral structural support normally provided by the fibula.

Question 57

A patient with Cleidocranial Dysplasia is undergoing an orthopedic evaluation. Which of the following is the underlying genetic and pathophysiologic mechanism for this condition?

Explanation

Cleidocranial dysplasia is an autosomal dominant disorder caused by a mutation in the RUNX2 (CBFA1) gene. It primarily affects bones formed by intramembranous ossification, such as the clavicles and cranial vault.

Question 58

A 6-month-old infant with developmental dysplasia of the hip (DDH) is being evaluated for closed reduction. A pre-procedural arthrogram demonstrates an "hourglass" constriction of the capsule. Which anatomical structure is responsible for this constriction?

Explanation

In long-standing DDH, the capsular constriction that creates the classic "hourglass" appearance on arthrography is caused by the tight iliopsoas tendon crossing over the anterior capsule.

Question 59

A 5-year-old boy presents with a prominent bump on the medial aspect of his foot and in-toeing. Clinical examination reveals a "Z-foot" deformity. He has a history of treated clubfoot. What is the primary pathoanatomy of the "skewfoot" deformity?

Explanation

Skewfoot (or Z-foot) is a complex deformity characterized by severe metatarsus adductus, lateral translation/abduction of the midfoot at the Chopart joint, and hindfoot valgus.

Question 60

Which of the following skeletal dysplasias is inherited in an X-linked dominant fashion and presents with lower extremity bowing, widened physes, and hypophosphatemia that does not respond to standard doses of Vitamin D?

Explanation

Familial hypophosphatemic rickets (Vitamin D-resistant rickets) is typically an X-linked dominant disorder caused by a PHEX mutation. It leads to renal phosphate wasting, presenting with short stature and rickets-like bone changes.

Question 61

A 3-month-old infant presents with a rigid rocker-bottom foot. Radiographs demonstrate a dorsally displaced navicular that does not reduce on a maximum plantar flexion lateral view. Which of the following is the most likely diagnosis?

Explanation

Congenital vertical talus is characterized by a rigid rocker-bottom deformity and a dorsally dislocated navicular on the talus. Irreducibility of the talonavicular joint on a forced plantar flexion lateral radiograph confirms the diagnosis.

Question 62

According to the Ponseti method for the treatment of congenital talipes equinovarus, what is the correct sequence of deformity correction?

Explanation

The correct sequence of correction in the Ponseti method follows the acronym CAVE: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by supinating the forefoot to align it with the hindfoot.

Question 63

A 13-year-old boy presents with recurrent ankle sprains and rigid flatfeet. Radiographs reveal a 'C-sign' on the lateral view. Which of the following represents the most likely anatomical location of the anomaly?

Explanation

The 'C-sign' on a lateral radiograph is highly indicative of a talocalcaneal (subtalar) coalition, representing a continuous bony bridge between the talar dome and the sustentaculum tali. Calcaneonavicular coalitions typically present with an 'anteater' sign.

Question 64

A 5-year-old boy with achondroplasia presents with progressively decreasing exercise tolerance, hyperreflexia, and clonus. What is the most critical anatomical site requiring urgent evaluation?

Explanation

Children with achondroplasia are at high risk for foramen magnum stenosis, which can compress the cervicomedullary junction. Symptoms of myelopathy, such as hyperreflexia and clonus, warrant urgent MRI and potential surgical decompression.

Question 65

A newborn is diagnosed with diastrophic dysplasia. Which of the following genetic mutations is responsible for this condition?

Explanation

Diastrophic dysplasia is an autosomal recessive condition caused by mutations in the SLC26A2 gene, which encodes a sulfate transporter. Clinical features include hitchhiker thumbs, cauliflower ears, and severe cervical kyphosis.

Question 66

A 7-year-old child with Morquio syndrome (MPS IV) presents for preoperative evaluation before bilateral lower extremity osteotomies. Which of the following preoperative imaging studies is most critical for preventing a catastrophic perioperative complication?

Explanation

Patients with Morquio syndrome frequently have odontoid hypoplasia and severe atlantoaxial instability. Flexion-extension cervical radiographs are critical prior to intubation to prevent spinal cord injury during positioning.

Question 67

Which of the following clinical findings is most characteristically associated with fibular hemimelia?

Explanation

Fibular hemimelia is characteristically associated with anteromedial bowing of the tibia, shortening of the limb, a ball-and-socket ankle joint, and absence of lateral foot rays. Anterolateral bowing is associated with congenital pseudarthrosis of the tibia.

Question 68

A 4-year-old child successfully treated for bilateral idiopathic clubfeet with the Ponseti method presents with a dynamic supination deformity of the foot during the swing phase of gait. Passive range of motion is full. What is the most appropriate management?

Explanation

Dynamic supination during the swing phase in a toddler previously treated for clubfoot is best managed by transferring the tibialis anterior tendon to the third cuneiform (TATT). This restores muscle balance and prevents fixed recurrent deformity.

Question 69

A 2-year-old girl is referred for an anterolateral bowing of her tibia that recently fractured. Which of the following systemic conditions is most strongly associated with this pathology?

Explanation

Anterolateral bowing of the tibia that fractures and fails to heal is characteristic of congenital pseudarthrosis of the tibia (CPT). Over 50% of CPT cases are highly associated with Neurofibromatosis type 1 (NF1).

Question 70

A 3-year-old with frequent fractures, blue sclerae, and dentinogenesis imperfecta is started on intravenous pamidronate. What is the primary mechanism of action of this medication in treating her condition?

Explanation

Pamidronate is a bisphosphonate that inhibits osteoclast activity, thereby decreasing bone resorption and increasing overall bone mineral density. This reduces fracture frequency in patients with osteogenesis imperfecta.

Question 71

A patient with Spondyloepiphyseal Dysplasia congenita (SEDc) is likely to have a defect involving which of the following molecules?

Explanation

SEDc is an autosomal dominant condition caused by mutations in the COL2A1 gene, resulting in defective Type II collagen. This primarily affects hyaline cartilage, leading to a short-trunk dwarfism, coxa vara, and ocular complications.

Question 72

A 14-year-old boy with multiple palpable bony prominences around his knees and shoulders is diagnosed with Multiple Hereditary Exostoses (MHE). The genetic mutation in this condition directly impairs the synthesis of which substance?

Explanation

MHE is caused by mutations in the EXT1 or EXT2 genes, which encode glycosyltransferases essential for the biosynthesis of heparan sulfate. Loss of heparan sulfate leads to abnormal Indian hedgehog (Ihh) signaling and aberrant cartilage growth.

Question 73

A 4-year-old child presents with severe varus bowing of the lower extremities, short stature, and a waddling gait. Laboratory studies reveal normal serum calcium, markedly low serum phosphate, and elevated alkaline phosphatase. Which of the following is the hallmark molecular pathogenesis?

Explanation

X-linked hypophosphatemic rickets is caused by a PHEX mutation leading to elevated FGF23 levels. FGF23 causes profound renal phosphate wasting and inhibits calcitriol synthesis, leading to rickets that does not respond to standard vitamin D supplementation.

Question 74

An infant is evaluated for an intoeing gait. Examination reveals metatarsus adductus with a heel bisector line passing through the third web space. The deformity is actively correctable to the midline with tickling of the lateral foot. What is the most appropriate initial management?

Explanation

Flexible metatarsus adductus that actively corrects to midline (Bleck classification) resolves spontaneously in over 90% of cases. Observation and reassurance are the most appropriate management for this benign condition.

Question 75

A 9-year-old girl is noted to have excessive mobility of her shoulders, allowing them to touch in the midline. Pelvic radiographs would most likely reveal which of the following abnormalities?

Explanation

The patient has Cleidocranial Dysplasia, caused by a RUNX2 mutation affecting intramembranous ossification. Key radiographic findings include hypoplastic or absent clavicles, delayed cranial suture closure, and a significantly widened pubic symphysis.

Question 76

A 6-year-old boy presents with a limp and midfoot pain. Radiographs demonstrate sclerosis and flattening of the navicular bone without signs of infection. What is the most appropriate treatment?

Explanation

The diagnosis is Kohler disease, an idiopathic avascular necrosis of the navicular bone. It is a self-limiting condition; severe pain is best treated with a short-leg walking cast for symptomatic relief while awaiting spontaneous revascularization.

Question 77

A 10-year-old boy presents with insidious onset of hindfoot pain and recurrent ankle sprains. Examination shows a rigid flatfoot with restricted subtalar motion and peroneal muscle spasm. Which tarsal coalition is most likely present given the patient's age and presentation?

Explanation

Calcaneonavicular coalitions typically ossify and become symptomatic between 8 and 12 years of age, presenting with a rigid flatfoot and peroneal spasticity. Talocalcaneal coalitions typically ossify and become symptomatic slightly later, between 12 and 16 years of age.

Question 78

In an infant with an untreated idiopathic clubfoot, the talus exhibits which of the following primary anatomical abnormalities?

Explanation

In idiopathic clubfoot (CTEV), the primary bony deformity involves the talus, which is smaller than normal, with its neck shortened and deviated medially and plantarly. The calcaneus, navicular, and cuboid are rotated medially around this deformed talus.

Question 79

A 2-year-old girl is evaluated for bilateral genu varum. Radiographs reveal a metaphyseal-diaphyseal angle (Drennan's angle) of 18 degrees and medial physeal beaking. What is the recommended management?

Explanation

The clinical and radiographic findings (metaphyseal-diaphyseal angle > 16 degrees) are highly suggestive of infantile Blount disease. Bracing with KAFOs is the standard initial treatment for stages I and II in children under 3 years of age.

Question 80

A 2-year-old boy presents with relapsed clubfoot after initial successful Ponseti casting. What is the most common cause of this recurrence?

Explanation

Non-compliance with the foot abduction brace is the most common cause of clubfoot relapse after successful Ponseti casting. Bracing is crucial up to age 4 to prevent recurrence.

Question 81

In a patient with congenital vertical talus, which of the following is the hallmark radiographic finding on a lateral radiograph in maximum plantarflexion?

Explanation

Congenital vertical talus is defined by a rigid dorsal dislocation of the navicular on the talus. This dislocation does not reduce on a maximum plantarflexion lateral radiograph, distinguishing it from an oblique talus.

Question 82

A 12-year-old boy complains of vague lateral hindfoot pain and frequent ankle sprains. Radiographs show a "C sign" on the lateral view. Which interpositional material is most appropriate after surgical resection of this anomaly?

Explanation

The "C sign" indicates a talocalcaneal coalition. After surgical resection, an autologous fat graft is the preferred interpositional material to prevent recurrence of this specific coalition.

Question 83

An infant with achondroplasia presents with central sleep apnea, hypotonia, and hyperreflexia. What is the most appropriate next step in management?

Explanation

These neurological findings suggest cervicomedullary compression at the foramen magnum, a life-threatening complication in infants with achondroplasia. An MRI of the craniocervical junction is essential for diagnosis before urgent decompression.

Question 84

A newborn presents with short-limbed dwarfism, "cauliflower" ears, hitchhiker thumbs, and severe rigid clubfeet. This condition is caused by a mutation in a gene responsible for transporting which of the following?

Explanation

The patient has diastrophic dysplasia, which is caused by a defect in the SLC26A2 gene. This gene encodes a diastrophic dysplasia sulfate transporter (DTDST), leading to defective sulfation of proteoglycans.

Question 85

A 4-year-old boy with a relapsed clubfoot presents with dynamic forefoot supination during the swing phase of gait. His hindfoot remains plantigrade. Which of the following is the most appropriate surgical intervention?

Explanation

Dynamic forefoot supination in a relapsed clubfoot with a flexible hindfoot is best treated with a full tibialis anterior tendon transfer to the lateral cuneiform. This converts the deforming supinating force into a corrective dorsiflexor.

Question 86

According to the Ponseti method of clubfoot correction, what is the correct sequence of deformity correction?

Explanation

The mnemonic CAVE dictates the standard Ponseti sequence: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by supinating the forefoot and elevating the first ray to align it with the hindfoot.

Question 87

A 3-year-old child presents with Morquio syndrome (MPS IV). Which of the following cervical spine abnormalities is the most critical to screen for in this patient to prevent sudden death?

Explanation

Patients with Morquio syndrome are at extraordinarily high risk for odontoid hypoplasia and ligamentous laxity. This results in severe atlantoaxial instability that can lead to fatal cervical myelopathy if unaddressed.

Question 88

A newborn is diagnosed with congenital posteromedial bowing of the tibia. What is the expected long-term clinical outcome of this condition if left untreated?

Explanation

Congenital posteromedial bowing of the tibia typically resolves spontaneously regarding the angular deformity. However, patients inevitably develop a significant leg-length discrepancy requiring a shoe lift or eventual epiphysiodesis.

Question 89

An 8-year-old child with a known mutation in the COL2A1 gene is evaluated in the clinic. Which of the following ophthalmic complications must this patient be closely monitored for?

Explanation

Mutations in the COL2A1 gene cause Type II collagenopathies, such as Spondyloepiphyseal Dysplasia (SED). These patients are at a high risk for severe myopia and subsequent retinal detachment.

Question 90

A 13-year-old girl with renal osteodystrophy undergoes surgical pinning for a severe left Slipped Capital Femoral Epiphysis (SCFE). What is the primary indication for prophylactic pinning of her contralateral asymptomatic hip?

Explanation

Prophylactic pinning of the contralateral hip is highly indicated in patients with SCFE associated with endocrine or metabolic disorders (e.g., renal osteodystrophy, hypothyroidism). These conditions carry a near 100% risk of eventual bilateral involvement.

Question 91

An 18-month-old child with infantile Blount disease is evaluated. Which of the following radiographic parameters best differentiates this condition from physiologic bowing?

Explanation

The metaphyseal-diaphyseal angle (Drennan's angle) is crucial for differentiating infantile Blount disease from physiologic bowing. An angle greater than 16 degrees is highly predictive of progressive Blount disease requiring intervention.

Question 92

A patient with severe Osteogenesis Imperfecta (Type III) has been receiving intravenous bisphosphonate therapy. What is the primary cellular mechanism of action for this class of medication?

Explanation

Nitrogen-containing bisphosphonates (like pamidronate) inhibit farnesyl pyrophosphate synthase in the mevalonate pathway. This prevents proper protein prenylation in osteoclasts, leading to early apoptosis and reduced bone resorption.

Question 93

A 6-month-old boy with Developmental Dysplasia of the Hip (DDH) has failed Pavlik harness treatment. A closed reduction and spica casting are planned. To minimize the risk of osteonecrosis of the femoral head, what defines the "safe zone" of positioning described by Ramsey?

Explanation

Ramsey's safe zone for DDH closed reduction is the arc between the angle of maximum abduction (which risks AVN if pushed too far) and the angle at which the hip redislocates in adduction. Spica casting should immobilize the hip within this safe arc.

Question 94

Which of the following combined clinical features is pathognomonic for Cleidocranial Dysplasia?

Explanation

Cleidocranial dysplasia (RUNX2 gene mutation) is classically characterized by delayed or absent closure of the cranial fontanelles, hypoplastic or absent clavicles, and retained deciduous teeth.

Question 95

A 9-year-old boy presents with a painful rigid flatfoot. Radiographs confirm a calcaneonavicular coalition. Which non-operative management strategy is generally considered the most appropriate initial treatment?

Explanation

Initial conservative management for a symptomatic tarsal coalition usually involves rigid immobilization in a short leg walking cast for 4 to 6 weeks to reduce joint inflammation and peroneal muscle spasms. Orthotics are often poorly tolerated in a rigid flatfoot.

Question 96

In Legg-Calve-Perthes disease, the lateral pillar classification is used to determine prognosis. At what stage of the disease is this classification most accurately applied to guide treatment?

Explanation

The lateral pillar (Herring) classification determines the retained height of the lateral pillar of the femoral head. It is most accurate and prognostically valuable when assessed during the early to late fragmentation phase of the disease.

Question 97

A 14-year-old boy with a BMI of 35 presents with knee pain and is diagnosed with a unilateral slipped capital femoral epiphysis (SCFE). Which of the following best describes the anatomical direction of the epiphyseal slip relative to the femoral neck?

Explanation

In SCFE, the femoral neck typically displaces anteriorly and superiorly. This means the epiphysis, which stays relatively reduced in the acetabulum, slips posteriorly and inferiorly relative to the femoral neck.

Question 98

A 2-year-old girl is noted to have an abnormal intoeing gait. Examination reveals severe femoral anteversion and internal tibial torsion. What is the typical natural history of this combination of rotational deformities?

Explanation

Increased femoral anteversion and internal tibial torsion in a toddler generally improve spontaneously with normal skeletal growth. They typically resolve without surgical or orthotic intervention by age 8 to 10 years.

Orthopedic Prometric MCQs - Chapter 3 Part 1

Orthopedic Prometric MCQs - Chapter 3 Part 6

Orthopedic Prometric MCQs - Chapter 3 Part 6

Chapter Index