Question 1

A 15-year-old girl is experiencing progressive weakness. She is unable to abduct her arms above 100° (pic). She has a progressive lordosis. Her facial expression is flat, and she cannot smile. Her mother has the same constellation of findings. No scoliosis is present. She and her mother are able to walk independently. The most likely diagnosis is:

Explanation

Orthopedic Prometric Exam Chapter 3 Image

This patient most likely has facioscapulohumeral dystrophy. With a frequency of 1:20,000, it is a rare disorder inherited in an autosomal- dominant fashion. The genetic abnormality is found on chromosome 4, with a decreased number of D4Z4 tandem repeats, but this does not appear to code for a protein product. Scoliosis is not present. In this condition, selective weakness of the serratus anterior, trapezius, and rhomboid muscles is present. Therefore, the scapula is not effectively stabilized against the trunk during use.

Question 2

A 10-year-old child, who has no history of fever, trauma, or infection, presents with minimal pain and a Trendelenburg gait on the left (Slide). Which of the following is the most likely diagnosis:

Explanation

This patient has fibrous dysplasia. The diffuse nature of the changes over a long portion of the bone, which includes blurring and thinning of the cortex, are classic signs of the disorder.

Question 3

A patient who does not walk outdoors or independently but can walk with a walker in physical therapy is listed as what level according to the Gross Motor Function Measure (GMFM):

Explanation

The GMF C lassification System (GMFC S) is a concise way of expressing overall motor ability. According to this system, level 1 is walking and running indoors and out with impaired speed, level 2 is impairment in running on uneven surfaces, level 3 is ambulation indoors and out with assistive devices, and level 4 is limited walking with a walker, and level 5 is nonambulatory.

Question 4

The patient shown in the clinical photograph (Slide 1) and radiograph (Slide 2) has which of the following conditions:

Explanation

This patient has Klippel-Trenaunay-Weber syndrome. This syndrome is characterized by a triad of cutaneous nevi, varicose veins, and limb overgrowth in length and/or width.

Question 5

An 8-year-old girl with no history of fever, illness, or weakness presents with an increasing spinal deformity. She was born in Asia. The patient is neurologically normal. Based on radiographs (Slide 1) and magnetic resonance images (Slide 2), the most likely diagnosis is:

Explanation

This patient has congenital kyphosis. The relative disk destruction with vertebral preservation argues against tuberculosis. The anterior bony wedging is atypical for remote bacterial infection. Anterior fusion is not seen in patients with Scheuermann kyphosis (rarely after maturity) or in patients with compression fractures.

Question 6

An 8-year-old boy presents with progressive deformity. Recommended management includes:

Explanation

This patient has a type II kyphosis (anterior bar). Because he is only 8 years old and the curve has progressed, further increase is likely. Observation is not indicated. Bracing has no influence on congenital curves. The kyphosis is >55° (78°) so a posterior fusion may not effectively halt the growth of these vertebral bodies in a posterior direction. Anterior and posterior fusion is the most likely procedure to control the curve.C orrect Answer: Anterior and posterior fusion 2291 A child with congenital below-elbow amputation is best fit with an active prosthesis at which age: A patient with congenital below-elbow amputation has sensation/proprioception in the limb and is able to perform most activities without assistance. Prostheses may interfere with crawling. Passive devices should not be started until walking begins, and active devices started at 2 to 4 years.

Question 7

Which of the following is the most specific feature of congenital vertical talus that distinguishes it from other deformities:

Explanation

The essential lesion in congenital vertical talus is a dorsolateral dislocation of the talonavicular joint.

Question 8

A 14-year-old boy sustains a hip dislocation in a motor vehicle accident. With closed reduction, he is at risk for all of the following except:

Explanation

With a hip dislocation in a young adolescent, occult injury to the physis may occur. Reports of physeal separation during the reduction, as well as entrapped osteochondral fragments appear in the literature. Degenerative joint disease may eventually develop due to the cartilage injury. Avascular necrosis risk is approximately 10%.

Question 9

A 12-year-old boy sustains a distal diaphyseal femur fracture with a large butterfly fragment. He weighs 110 lb. Which of the following treatments is most appropriate and best able to preserve alignment:

Explanation

A large butterfly fragment as well as the age and weight of the patient have been demonstrated to decrease the chances of success in treating children with femur fractures using flexible intramedullary nails. For similar reasons, the fracture is not suitable for an immediate spica or traction followed by functional bracing. The retrograde nail is not indicated due to open physis. Submuscular plate fixation is the best option.C orrect Answer: Submuscular plate fixation

Question 10

Which of the following risks is associated with inserting a rigid femoral intramedullary nail through the piriformis fossa in a 10- to 14-year-old child:

Explanation

Avascular necrosis is a risk if a nail is inserted through the piriformis fossa in a patient younger than 15 years of age with open physes.

Question 11

Which of the following is a description of a closed kinetic chain exercise:

Explanation

A closed kinetic chain exercise is one in which the ends of a limb are fixed from free movement by resistance.

Question 12

The action of bisphosphonates is primarily upon which component of bone:

Explanation

Bisphosphonates act to inhibit osteoclasts, thereby decreasing resorption and increasing bone mineral density in many conditions.

Question 13

Which of the following is not a common finding in patients with Prader- Willi syndrome:

Explanation

Prader-Willi syndrome is characterized by early hypotonia, short stature, severe obesity, developmental delay, scoliosis, and osteopenia.

Question 14

Which of the following disease processes is demonstrated in the radiograph (Slide):

Explanation

The left femoral epiphysis shows avascular changes characteristic of Legg-C alve-Perthes disease without slippage. Although developmental dysplasia of the hip may also be complicated by avascular changes, the femoral neck and acetabulum would manifest more longstanding growth alterations as well. The contralateral hip would be symmetric in patients with multiple epiphyseal dysplasia.

Question 15

Which of the following accurately describes this radiograph (Slide):

Orthopedic Prometric Exam Chapter 3 Image

Explanation

According to Herringâ s classification, this radiograph demonstrates a lateral pillar C because the lateral pillar is collapsed by more than 50%.

Question 16

An 11-year-old girl presents with bilateral painful flatfeet. A computed tomography image is shown (Slide). The most likely diagnosis is:

Orthopedic Prometric Exam Chapter 3 Image

Explanation

This patient has evolving medial talocalcaneal facet coalition. The computed tomography is remarkable for obliquity of the medial facet, along with irregularity and narrowing of this facet, which is not evident on plain radiographs. Normally the medial subtalar facet should be parallel to the posterior facet. Treatment options for this patient include immobilization, resection, or subtalar fusion.

Question 17

Which of the following is not a common feature of constriction band syndrome:

Explanation

Constriction band syndrome is not commonly associated with developmental dislocation of the hip. However, annular rings, fenestrated syndactyly, digital amputation, and equinovarus foot are often seen in patients with constriction band syndrome.

Question 18

An 8-year-old child presents with a mass on the posteromedial side of the popliteal fossa. The mass, which has been present for more than 1 month, is nontender and moderately soft. The knee examination is stable. No knee effusion is present, and the patient has no signs or symptoms of infection. Radiographs are normal. Which of the following is the next step to aid in diagnosis:

Explanation

This patient demonstrates the classic presentation of a popliteal cyst. Transillumination often confirms the diagnosis of popliteal cyst, thereby avoiding the use of advanced imaging.

Question 19

Which of the following features is not associated with congenital muscular torticollis:

Explanation

Congenital muscular torticollis is caused by in-utero molding, as are developmental dysplasia of the hip and metatarsus adductus. Contralateral occipital flattening and asymmetrical facial features develop secondarily with torticollis. Imperforate anus is associated with congenital hemivertebrae but not with muscular torticollis.

Question 20

A 3-month-old female infant presents with the dorsum of the foot almost in contact with the anterior tibia. She has no pain with movement; plantar flexion and inversion of the feet are not restricted, but there is difficulty in manipulating the foot to the neutral position. She is normal otherwise. Which of the following treatments is most appropriate:

Explanation

This is a patient with positional calcaneovalgus, which is a more common condition than congenital vertical talus (C VT). Patients with such deformity should be evaluated carefully and differentiated from the more serious CVT. In calcaneovalgus foot, the problem is in the ankle, which is in calcaneus position. The arch itself may be normal. In C VT, the ankle is normal and the problem is in the foot. The foot is essentially plantigrade, but the arch is reversed. Typically, a deep crease in the sinus tarsi and some forefoot abduction are present. No difference was found between the calcaneovalgus feet that underwent manipulation and casting versus observation alone, when assessed at 3 to 11 years of follow-up. Surgery is never required for a positional calcaneovalgus deformity, which is not true for C VT. Long-term prognosis of positional calcaneovalgus is excellent.

Question 21

A 6-year-old child with spastic diplegic cerebral palsy requires the use of a wheeled walker for mobility indoors and outdoors. They are transported in a manual wheelchair for long distances in the community. What is the appropriate Gross Motor Function Classification System (GMFCS) level?

Explanation

GMFCS Level III children walk using a hand-held mobility device in most indoor settings and use wheeled mobility for long distances. Level II children walk without devices but have limitations outdoors.

Question 22

A 4-year-old boy presents with frequent falls and difficulty climbing stairs. On examination, he exhibits pseudohypertrophy of the calves and a positive Gowers sign. Which of the following is the most definitive diagnostic test for this condition?

Explanation

Duchenne muscular dystrophy is an X-linked recessive disorder caused by a mutation in the dystrophin gene. Genetic testing is the gold standard and most definitive diagnostic test, largely replacing muscle biopsies.

Question 23

A 7-year-old boy is diagnosed with Legg-Calve-Perthes disease.

Which of the following radiographic findings is considered a "head-at-risk" sign described by Catterall?

Explanation

Gage sign is a V-shaped radiolucency in the lateral epiphysis and adjacent metaphysis. It represents a Catterall "head-at-risk" sign in Legg-Calve-Perthes disease, indicating a potential for a poor outcome.

Question 24

A 2-year-old child with Spinal Muscular Atrophy (SMA) type II presents for scoliosis evaluation. Which of the following medical therapies has recently revolutionized the treatment of SMA by modifying the SMN2 gene splicing to produce functional SMN protein?

Explanation

Nusinersen (Spinraza) is an antisense oligonucleotide that alters the splicing of SMN2 pre-mRNA. This increases the production of fully functional SMN protein, significantly improving motor function in SMA patients.

Question 25

During computerized gait analysis of a child with spastic diplegic cerebral palsy, the kinematic data reveals excessive knee flexion during the stance phase (crouch gait). Which of the following interventions is most likely to exacerbate this specific gait abnormality?

Explanation

Achilles tendon lengthening weakens the calf muscles (plantarflexors). The plantarflexor-knee extension couple is crucial for maintaining knee extension during stance, so weakening it exacerbates crouch gait.

Question 26

A 12-year-old boy with Charcot-Marie-Tooth disease presents with a progressive rigid cavovarus foot deformity.

Examination reveals a positive Coleman block test indicating hindfoot flexibility. The deformity is primarily driven by the relative overactivity of which muscle?

Explanation

In Charcot-Marie-Tooth disease, the tibialis anterior and peroneus brevis weaken early. The relatively preserved peroneus longus overpowers the tibialis anterior, causing plantarflexion of the first ray and driving the forefoot-driven cavovarus deformity.

Question 27

A 13-year-old obese boy underwent in situ pinning for a stable slipped capital femoral epiphysis (SCFE) 6 months ago. He now complains of progressive hip stiffness and pain. Radiographs reveal a narrowed joint space with periarticular osteopenia. What is the most likely cause of this complication?

Explanation

Chondrolysis is a known complication of SCFE characterized by progressive joint space narrowing and stiffness. It is strongly associated with unrecognized pin penetration into the joint space.

Question 28

A newborn with a myelomeningocele at the L4 level is evaluated in the nursery. What is the most likely hip pathology expected in this patient over time?

Explanation

Patients with an L4 motor level have intact hip flexors and adductors but lack strong hip extensors and abductors. This unopposed muscle action frequently leads to paralytic hip subluxation and dislocation.

Question 29

Which of the following patients with Cerebral Palsy is the most ideal candidate for Selective Dorsal Rhizotomy (SDR)?

Explanation

The ideal candidate for SDR is a child aged 3 to 8 years with spastic diplegia, good cognition, minimal fixed contractures, and good underlying selective motor control. It is generally contraindicated in dyskinetic or dystonic CP.

Question 30

A 3-year-old girl is diagnosed with a neglected unilateral developmental dysplasia of the hip (DDH).

The femoral head is dislocated superiorly. What is the most appropriate surgical management?

Explanation

In children over 2 to 3 years old with a high dislocation, open reduction typically requires a concurrent femoral shortening osteotomy to reduce pressure on the femoral head and a pelvic osteotomy for adequate acetabular coverage.

Question 31

In a patient diagnosed with a unilateral slipped capital femoral epiphysis (SCFE), which of the following is an absolute indication for prophylactic pinning of the contralateral asymptomatic hip?

Explanation

Endocrine disorders (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency) significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these cases.

Question 32

A 16-year-old boy presents with slowly progressive proximal muscle weakness. Muscle biopsy reveals reduced, but not absent, levels of dystrophin. He is diagnosed with Becker muscular dystrophy (BMD). What is the genetic transmission pattern of this disease?

Explanation

Both Duchenne and Becker muscular dystrophies are X-linked recessive disorders caused by mutations in the dystrophin gene. In BMD, the mutation allows for the production of a partially functional, truncated dystrophin protein.

Question 33

According to consensus guidelines for hip surveillance in children with cerebral palsy, at what Gross Motor Function Classification System (GMFCS) level is the risk of hip displacement the highest, necessitating the most frequent radiographic screening?

Explanation

The risk of hip displacement in CP is directly proportional to the severity of neurologic involvement. Children at GMFCS Level V have the highest risk (approaching 90%) and require the most frequent radiographic surveillance.

Question 34

A 12-year-old child with spastic diplegic cerebral palsy presents with a progressive crouch gait. Which of the following prior surgical interventions is the most common iatrogenic cause of this gait pattern?

Explanation

Over-lengthening of the Achilles tendon leads to calcaneus gait and triceps surae weakness. This causes failure of the plantar flexion-knee extension couple, resulting in an iatrogenic crouch gait.

Question 35

A 13-year-old boy presents with a rigid flatfoot and frequent recurrent ankle sprains. Radiographs reveal a continuous 'C-sign' on the lateral foot view. Which of the following physical examination findings is most characteristic of this condition?

Explanation

The 'C-sign' indicates a talocalcaneal coalition. Patients typically present with a rigid flatfoot, decreased subtalar motion, and secondary peroneal spasticity.

Question 36

A 6-week-old female infant is placed in a Pavlik harness for a dislocated left hip (Ortolani positive). After 3 weeks of strict full-time harness wear, ultrasound shows the hip remains persistently dislocated. What is the most appropriate next step in management?

Explanation

Failure to reduce a dislocated hip after 3 weeks in a Pavlik harness is an indication to abandon the harness to prevent 'Pavlik harness disease' (posterior acetabular wear). The next step is typically closed reduction and spica casting under anesthesia.

Question 37

A 12-year-old obese boy presents to the emergency department unable to bear weight on his right leg after a minor fall. Radiographs confirm a severe, unstable slipped capital femoral epiphysis (SCFE). Which blood supply to the femoral head is most at risk of injury in this acute, unstable scenario?

Explanation

The medial circumflex femoral artery (MCFA) provides the primary blood supply to the femoral head via its ascending cervical branches. In an unstable SCFE, these extraosseous vessels are tethered and highly susceptible to rupture or occlusion, leading to osteonecrosis.

Question 38

In the Ponseti method for treating idiopathic clubfoot, what is the correct sequence of deformity correction?

Explanation

The CAVE mnemonic dictates the order of correction in the Ponseti method: Cavus (by elevating the first ray), Adductus, Varus, and finally Equinus (usually requiring a percutaneous Achilles tenotomy).

Question 39

A 4-year-old girl with blue sclerae, dentinogenesis imperfecta, and multiple prior long bone fractures is diagnosed with osteogenesis imperfecta. This condition is most commonly caused by a mutation affecting which of the following?

Explanation

Osteogenesis imperfecta is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode the chains of Type I collagen. This leads to brittle bones, blue sclerae, and hearing loss.

Question 40

According to the Herring Lateral Pillar classification for Legg-Calve-Perthes disease, a hip in which the lateral pillar maintains between 50% and 100% of its original height is classified as:

Explanation

In the Herring classification, Type A has no lateral pillar involvement. Type B maintains >50% lateral pillar height. Type C has <50% height maintained, portending a worse prognosis.

Question 41

A 2-year-old child with achondroplasia presents with delayed motor milestones, hypotonia, and sleep apnea. Which of the following is the most critical anatomical area to evaluate immediately?

Explanation

Foramen magnum stenosis is a life-threatening complication in infants and young children with achondroplasia. It can cause cervicomedullary compression, leading to central sleep apnea, hypotonia, and sudden death.

Question 42

A 9-year-old boy with Duchenne muscular dystrophy is referred for progressive neuromuscular scoliosis. At what point in the disease progression is posterior spinal fusion typically indicated?

Explanation

In DMD, scoliosis usually progresses rapidly after wheelchair dependence. Spinal fusion is indicated for curves >20-30 degrees in non-ambulatory patients, ideally performed while the FVC is still >35% to minimize pulmonary complications.

Question 43

A 7-year-old boy with spastic diplegic cerebral palsy presents with worsening crouch gait. He previously underwent isolated heel cord lengthening at age 4. Physical exam shows tight hamstrings and excessive ankle dorsiflexion. What is the most likely iatrogenic cause of his crouch gait?

Explanation

Over-lengthening of the Achilles tendon in a child with CP removes the plantarflexion-knee extension couple, leading to excessive dorsiflexion and crouch gait. Concomitant unaddressed hamstring tightness exacerbates knee flexion.

Question 44

A 4-year-old girl with cerebral palsy (GMFCS Level IV) undergoes routine radiographic hip surveillance. The AP pelvis radiograph demonstrates a Reimers' migration percentage of 45%. What is the most appropriate next step in management?

Explanation

In CP patients, a migration percentage >40-50% generally warrants bony reconstructive surgery (VDRO and pelvic osteotomy) to prevent dislocation. Soft tissue releases alone are insufficient for migration >40%.

Question 45

A 12-year-old boy weighing 90 kg presents with acute on chronic left knee and groin pain. He is unable to bear weight. Radiographs show a posterior and inferior displacement of the proximal femoral epiphysis. What is the most serious complication associated with the appropriate initial surgical treatment of this condition?

Explanation

The clinical picture describes an unstable slipped capital femoral epiphysis (SCFE). Unstable SCFE has a high risk of avascular necrosis (AVN), which can occur naturally or be exacerbated by surgical reduction and fixation.

Question 46

A 6-week-old female infant is treated with a Pavlik harness for a dislocated left hip. After 3 weeks of strict harness wear, ultrasound reveals that the hip remains persistently dislocated. What is the most appropriate next step in management?

Explanation

Failure to reduce a dislocated hip after 3 weeks of Pavlik harness wear is an indication to abandon the harness to avoid Pavlik harness disease (posterior acetabular wear). The next step is a closed reduction and spica casting.

Question 47

During the Ponseti method for clubfoot correction, the physician must sequentially correct the deformities. Which of the following describes the correct order of correction and the anatomical fulcrum used during manipulation?

Explanation

The Ponseti method corrects deformities in the CAVE sequence (Cavus, Adductus, Varus, Equinus). The manipulation involves supinating the forefoot to correct cavus, then abducting the foot using the lateral head of the talus as the fulcrum.

Question 48

A 13-year-old boy presents with progressive right hip pain and stiffness 6 months after in situ pinning of a stable slipped capital femoral epiphysis. Examination reveals significant restriction of all hip motions, particularly internal rotation and abduction. Radiographs show symmetric narrowing of the joint space. What is the most likely diagnosis?

Explanation

Chondrolysis is characterized by acute or insidious onset of pain, stiffness, and symmetric joint space narrowing (typically <3 mm) after SCFE. It may be associated with unrecognized screw penetration into the joint.

Question 49

A 6-year-old boy presents with a painless limp. Radiographs reveal fragmentation and sclerosis of the proximal femoral epiphysis. According to the lateral pillar classification for Legg-Calvé-Perthes disease, which radiographic finding constitutes a Group C categorization?

Explanation

In the Herring lateral pillar classification of Perthes disease, Group C involves <50% maintenance of the lateral pillar height. This group has a poor prognosis and a higher risk of aspherical healing.

Question 50

A 4-year-old boy presents with calf pseudohypertrophy, a waddling gait, and uses his hands to push on his legs to stand up from the floor. Genetic testing reveals a mutation in the dystrophin gene. Which of the following is the most appropriate initial orthopedic consideration?

Explanation

The boy has Duchenne Muscular Dystrophy (DMD). Systemic corticosteroids are the mainstay of medical treatment to prolong ambulation and preserve pulmonary and cardiac function. Orthopedic interventions occur later as the disease progresses.

Question 51

A 3-month-old infant is diagnosed with achondroplasia. What is the most critical neurological complication to screen for during the first year of life?

Explanation

Foramen magnum stenosis is a life-threatening complication in infants with achondroplasia, potentially causing cervicomedullary compression, central sleep apnea, and sudden death. It requires careful clinical screening.

Question 52

A newborn presents with severe hypotonia, absent deep tendon reflexes, and paradoxical breathing. Genetic testing confirms a homozygous deletion of the SMN1 gene. What is the diagnosis and its inheritance pattern?

Explanation

Spinal Muscular Atrophy (SMA) Type 1 (Werdnig-Hoffmann disease) presents with severe hypotonia in early infancy and is caused by an SMN1 gene deletion. It is inherited in an autosomal recessive manner.

Question 53

A 3-year-old child with blue sclerae, dentinogenesis imperfecta, and multiple fractures with minimal trauma is evaluated. She is diagnosed with Osteogenesis Imperfecta (OI). Which molecular defect is most likely responsible?

Explanation

Osteogenesis Imperfecta is primarily caused by mutations in the COL1A1 or COL1A2 genes, which encode type I collagen. This leads to brittle bones, blue sclerae, and varying degrees of skeletal deformity.

Question 54

A 4-year-old boy presents with delayed motor milestones and uses his hands to walk up his thighs to stand. Laboratory testing reveals significantly elevated creatine kinase. A muscle biopsy would most likely show an absence of which protein?

Explanation

The clinical presentation describes Gowers' sign, hallmark for Duchenne Muscular Dystrophy (DMD). DMD is an X-linked recessive disorder caused by a mutation in the DMD gene, leading to absent dystrophin protein.

Question 55

According to best practice guidelines for cerebral palsy hip surveillance, how frequently should a non-ambulatory 6-year-old child (GMFCS Level V) undergo radiographic screening of the hips?

Explanation

Children with GMFCS levels IV and V are at the highest risk for hip displacement. Current surveillance guidelines recommend radiographic screening every 6 months for these patients until skeletal maturity or stabilization.

Question 56

A 2-year-old boy has profound hypotonia, absent deep tendon reflexes, and fine fasciculations of the tongue. He is able to sit independently but cannot pull to stand or walk. Genetic testing reveals a deletion in the SMN1 gene. What is the most likely orthopedic complication he will develop?

Explanation

The patient has Spinal Muscular Atrophy (SMA) Type II. The most common and significant orthopedic complication in non-ambulatory SMA patients is early-onset, progressive scoliosis.

Question 57

A 12-year-old obese male presents with a 3-week history of left groin pain and a limp. Physical examination reveals obligate external rotation of the left hip during passive flexion. Based on the clinical presentation and image provided, what is the most appropriate initial management for this stable deformity?

Explanation

The patient has a stable Slipped Capital Femoral Epiphysis (SCFE). The gold standard treatment is in situ fixation with a single percutaneous screw to prevent further slippage.

Question 58

An 8-year-old boy presents with a painless limp of 4 months duration. Anteroposterior pelvis radiograph demonstrates fragmentation of the capital femoral epiphysis with >50% loss of lateral pillar height. According to the Herring Lateral Pillar classification, what group does this represent?

Explanation

In the Herring Lateral Pillar classification for Legg-Calvé-Perthes disease, Group C is defined by >50% collapse of the lateral pillar height. This indicates a poor prognosis.

Question 59

A 14-year-old boy presents with frequent ankle sprains and rigid, painful flatfeet. Oblique radiographs of the foot reveal an "anteater nose" sign. What is the most appropriate initial surgical intervention if conservative management fails?

Explanation

The "anteater nose" sign is pathognomonic for a calcaneonavicular coalition. The standard surgical treatment after failed conservative care is resection of the coalition with interposition of fat or the extensor digitorum brevis muscle.

Question 60

A 5-year-old boy presents with anterolateral bowing of the tibia and multiple café-au-lait macules. Radiographs demonstrate diaphyseal narrowing and a pseudarthrosis. What is the primary underlying cellular defect in the pseudarthrosis tissue?

Explanation

Congenital pseudarthrosis of the tibia in Neurofibromatosis Type 1 (NF1) is driven by a local loss of neurofibromin. This leads to increased osteoclast activity and diminished osteoblast function in the local hamartomatous tissue.

Question 61

A 3-year-old girl with achondroplasia develops worsening hypotonia, hyperreflexia in the lower extremities, and newly recognized central sleep apnea. What is the most crucial next step in management?

Explanation

These findings indicate cervicomedullary compression secondary to foramen magnum stenosis, a life-threatening complication of achondroplasia. Urgent MRI and neurosurgical decompression are required.

Orthopedic Prometric MCQs - Chapter 3 Part 1

Orthopedic Prometric MCQs - Chapter 3 Part 15

Orthopedic Prometric MCQs - Chapter 3 Part 15

Chapter Index