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4. Pediatrics MCQs

Practice Set 316 of 334

This practice set contains high-yield board review questions covering key concepts in 4. Pediatrics. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 6301

Topic: Pediatric Hip
An 8-year-old boy presents with a painless limp of 3 months duration. Radiographs show fragmentation of the capital femoral epiphysis with lateral subluxation, consistent with Legg-Calvé-Perthes disease. Which of the following is considered the most significant prognostic factor for the long-term outcome of the hip?
. Gender of the patient
. Age at clinical onset
. Presence of a metaphyseal cyst
. Degree of restricted internal rotation
. Body mass index

Correct Answer & Explanation

. Age at clinical onset

Explanation

The most significant prognostic factor for the long-term outcome in Legg-Calvé-Perthes disease is the age of the patient at the onset of the disease. Children who develop the disease before the age of 6 generally have a good prognosis because they have more time for the femoral head to remodel before skeletal maturity. Children over the age of 8 at onset have a significantly worse prognosis and a higher likelihood of developing early osteoarthritis, as there is less remaining growth for remodeling. The lateral pillar classification (Herring) is the most important radiographic prognostic factor, but age remains the most critical overall clinical factor. While restricted motion and metaphyseal cysts are part of the clinical picture, they do not supersede age in prognostic value.

Question 6302

Topic: 4. Pediatrics

A 7-year-old girl with spastic quadriplegic cerebral palsy (GMFCS Level IV) is evaluated in the clinic. Her AP pelvis radiograph reveals a Reimers migration percentage of 55% on the right hip. Physical examination shows 20 degrees of hip abduction bilaterally. What is the most appropriate surgical intervention?

. Bilateral adductor tenotomies alone
. Varus derotational osteotomy (VDRO) of the proximal femur and pelvic osteotomy
. Proximal femoral resection (Castle procedure)
. Total hip arthroplasty
. Observation with repeat radiographs in 6 months

Correct Answer & Explanation

. Varus derotational osteotomy (VDRO) of the proximal femur and pelvic osteotomy

Explanation

Correct Answer: BHip displacement is a common and severe complication in children with cerebral palsy, particularly those with higher GMFCS levels (IV and V). The Reimers migration percentage measures the amount of the femoral head that is uncovered by the acetabulum. A migration percentage >50% in a 7-year-old indicates a subluxated/dislocated hip that requires bony reconstruction. Soft tissue releases alone (adductor tenotomies) are indicated for hips with a migration percentage between 30% and 40-50% in younger children (typically <4-5 years old) but have an unacceptably high failure rate once significant bony dysplasia and subluxation (>50%) have occurred. Therefore, a varus derotational osteotomy (VDRO) of the proximal femur combined with a pelvic osteotomy (e.g., Dega or San Diego) is the standard of care to restore hip joint congruity. Proximal femoral resection is a salvage procedure for painful, chronically dislocated hips in older, non-ambulatory patients. THA is rarely indicated in this age group.

Question 6303

Topic: 4. Pediatrics

A 4-year-old boy sustains a transverse femur fracture after a minor fall from a standing height. He has a history of multiple fractures, blue sclerae, and dentinogenesis imperfecta. A genetic defect affecting which of the following is the primary cause of his condition?

. Type II collagen synthesis
. Type I collagen synthesis
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)
. Core binding factor alpha 1 (CBFA1)

Correct Answer & Explanation

. Type I collagen synthesis

Explanation

Correct Answer: BThe patient's clinical presentation of recurrent fragility fractures, blue sclerae, and dentinogenesis imperfecta is classic for Osteogenesis Imperfecta (OI). OI is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode the alpha-1 and alpha-2 chains of Type I collagen. Type I collagen is the major structural protein in bone, skin, sclera, and dentin. Defects in Type II collagen are associated with chondrodysplasias (e.g., achondrogenesis). Mutations in FGFR3 cause achondroplasia. Mutations in COMP cause pseudoachondroplasia and multiple epiphyseal dysplasia (MED). Mutations in CBFA1 (RUNX2) cause cleidocranial dysplasia.

Question 6304

Topic: 4. Pediatrics
A 14-year-old boy sustains an ankle injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis. Which ligament is responsible for the avulsion of this specific fracture fragment?
. Anterior talofibular ligament
. Calcaneofibular ligament
. Anterior inferior tibiofibular ligament (AITFL)
. Posterior inferior tibiofibular ligament (PITFL)
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament (AITFL)

Explanation

The injury described is a juvenile Tillaux fracture, which is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. This fracture occurs in adolescents (typically 12-15 years old) due to the asymmetric closure pattern of the distal tibial physis. The physis closes first centrally, then anteromedially, then posteromedially, and finally laterally. When an external rotation force is applied to the foot during this specific window of skeletal maturity, the anterior inferior tibiofibular ligament (AITFL) avulses the anterolateral epiphysis, which is the only portion of the physis that remains open and vulnerable. The ATFL and CFL are lateral ankle ligaments involved in sprains. The PITFL is involved in Volkmann fractures (posterior malleolus). The deltoid is the medial ligament complex.

Question 6305

Topic: 4. Pediatrics
A 3-year-old obese African American girl presents with bilateral bowing of her legs. Standing AP radiographs of the lower extremities demonstrate a metaphyseal-diaphyseal angle (MDA) of 18 degrees and medial metaphyseal beaking of the proximal tibia bilaterally. What is the most appropriate initial management?
. Reassurance and observation for spontaneous resolution
. Vitamin D and calcium supplementation
. Knee-ankle-foot orthoses (KAFOs)
. Proximal tibial valgus osteotomy
. Guided growth with tension band plates

Correct Answer & Explanation

. Knee-ankle-foot orthoses (KAFOs)

Explanation

The patient has infantile Blount disease (tibia vara), characterized by pathologic varus deformity of the proximal tibia. Risk factors include early walking, obesity, and African American descent. Radiographically, a metaphyseal-diaphyseal angle (MDA) of greater than 16 degrees is highly predictive of Blount disease rather than physiologic bowing. For a child under the age of 4 with infantile Blount disease (Langenskiöld stages I or II), the initial treatment of choice is a trial of bracing with Knee-Ankle-Foot Orthoses (KAFOs) worn during weight-bearing activities. If the child is over 4 years old, or if bracing fails to correct the deformity after 1 year, surgical intervention (proximal tibial osteotomy) is indicated. Reassurance is appropriate for physiologic bowing (MDA < 11 degrees). Vitamin D is for rickets. Guided growth is generally reserved for older children or specific cases, but KAFO is the standard initial step for a 3-year-old.

Question 6306

Topic: 4. Pediatrics

A 6-year-old boy with spastic quadriplegic cerebral palsy (GMFCS Level V) presents for routine orthopaedic evaluation. Pelvic radiographs demonstrate a Reimers migration percentage of 45% bilaterally with early blunting of the acetabular sourcil. Physical examination reveals bilateral hip abduction of 20 degrees with the hips in extension. What is the most appropriate management?

. Observation and repeat radiographs in 6 months
. Bilateral adductor and iliopsoas tenotomies
. Bilateral varus derotational osteotomies (VDRO) and pelvic osteotomies
. Bilateral proximal femoral resection (Castle procedure)
. Selective dorsal rhizotomy

Correct Answer & Explanation

. Bilateral varus derotational osteotomies (VDRO) and pelvic osteotomies

Explanation

Correct Answer: Bilateral varus derotational osteotomies (VDRO) and pelvic osteotomiesIn children with cerebral palsy, hip displacement is common, particularly in those with higher GMFCS levels (Level IV and V). The Reimers migration percentage (MP) is used to quantify subluxation. An MP > 40% with associated bony changes (acetabular dysplasia) or severe contractures typically requires bony reconstruction. Soft tissue releases (adductor/psoas tenotomies) are generally reserved for younger children (typically < 4-5 years old) with an MP between 30% and 40% and no significant bony deformity. Because this patient has an MP of 45% and early acetabular changes, soft tissue release alone will likely fail to prevent further subluxation. Bilateral VDRO combined with pelvic osteotomies (such as a Dega or San Diego osteotomy) is the gold standard for reconstructing these hips. Proximal femoral resection is a salvage procedure reserved for painful, chronically dislocated hips in non-ambulatory patients who have failed other treatments or present late. Selective dorsal rhizotomy is a neurosurgical procedure to reduce spasticity, primarily indicated for ambulatory diplegic patients, and does not directly treat established hip dysplasia.

Question 6307

Topic: 4. Pediatrics

A 4-year-old girl sustains a low-energy diaphyseal femur fracture. Her medical history is significant for multiple prior fractures, blue sclerae, and dentinogenesis imperfecta. Genetic testing is most likely to reveal a mutation affecting the synthesis of which of the following proteins?

. Type II collagen
. Type I collagen
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)
. Core binding factor alpha 1 (CBFA1)

Correct Answer & Explanation

. Type I collagen

Explanation

Correct Answer: Type I collagenThis patient's clinical presentation is classic for Osteogenesis Imperfecta (OI), a genetic disorder characterized by bone fragility, blue sclerae, dentinogenesis imperfecta, and hearing loss. OI is predominantly caused by autosomal dominant mutations in theCOL1A1orCOL1A2genes, which encode the alpha-1 and alpha-2 chains of Type I collagen. Type I collagen is the major structural protein in bone, skin, dentin, and sclerae. Type II collagen mutations are associated with skeletal dysplasias such as achondrogenesis and spondyloepiphyseal dysplasia. FGFR3 mutations are the cause of achondroplasia, the most common form of short-limb dwarfism. Mutations in COMP cause pseudoachondroplasia and multiple epiphyseal dysplasia. CBFA1 (also known as RUNX2) mutations are responsible for cleidocranial dysplasia, characterized by absent or hypoplastic clavicles and delayed closure of cranial sutures.

Question 6308

Topic: 4. Pediatrics
A 3-year-old girl presents with progressive bowing of her left leg. Standing radiographs demonstrate a sharp varus deformity at the proximal tibial metaphysis. The metaphyseal-diaphyseal angle (MDA) is measured at 18 degrees. What is the most appropriate next step in management?
. Reassurance and annual observation
. Knee-ankle-foot orthosis (KAFO) during weight-bearing
. Proximal tibial valgus osteotomy
. Guided growth with a tension band plate
. Epiphysiodesis of the lateral proximal tibia

Correct Answer & Explanation

. Knee-ankle-foot orthosis (KAFO) during weight-bearing

Explanation

This patient has infantile Blount disease (tibia vara), characterized by abnormal endochondral ossification of the medial aspect of the proximal tibial physis. The metaphyseal-diaphyseal angle (MDA), described by Levine and Drennan, is crucial for differentiating physiologic bowing from Blount disease. An MDA > 16 degrees is highly predictive of progressive Blount disease. For children under the age of 3 to 4 years with an MDA > 16 degrees or progressive deformity (Langenskiöld stages I-II), the initial treatment of choice is bracing with a KAFO during weight-bearing activities. If bracing fails, or if the child presents at an older age (typically > 4 years) or with a more advanced Langenskiöld stage (III or higher), surgical intervention such as a proximal tibial valgus osteotomy is indicated. Guided growth (hemiepiphysiodesis) is an option for older children with open physes but is not the first-line treatment for a 3-year-old with an MDA of 18 degrees, where bracing is highly effective.

Question 6309

Topic: 4. Pediatrics
A 14-year-old boy sustains an ankle injury while skateboarding. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibia. The avulsed fragment is displaced 3 mm. Which of the following ligaments is responsible for the avulsion of this fracture fragment?
. Anterior talofibular ligament
. Calcaneofibular ligament
. Anterior inferior tibiofibular ligament
. Posterior inferior tibiofibular ligament
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament

Explanation

This patient has a juvenile Tillaux fracture, which is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. This fracture occurs in adolescents due to the asymmetric closure pattern of the distal tibial physis. The physis closes first centrally, then anteromedially, then posteromedially, and finally laterally. When an external rotation force is applied to the foot, the anterior inferior tibiofibular ligament (AITFL) becomes taut and avulses the anterolateral epiphysis, which is the last portion of the physis to close. The anterior talofibular and calcaneofibular ligaments are lateral ankle ligaments involved in inversion sprains. The posterior inferior tibiofibular ligament is involved in Volkmann fractures (posterior malleolus). The deltoid ligament is the primary medial stabilizer of the ankle.

Question 6310

Topic: 4. Pediatrics

A 2-year-old boy presents with anterolateral bowing of the tibia. Radiographs demonstrate a narrowed, sclerotic medullary canal at the apex of the deformity. Which of the following conditions is most strongly associated with this presentation?

. Fibrous dysplasia
. Neurofibromatosis type 1
. Osteogenesis imperfecta
. Achondroplasia
. Cleidocranial dysplasia

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Correct Answer: Neurofibromatosis type 1Anterolateral bowing of the tibia in a young child, especially with radiographic evidence of a narrowed, sclerotic medullary canal, is highly suspicious for congenital pseudarthrosis of the tibia (CPT). CPT is strongly associated with Neurofibromatosis type 1 (NF1), with approximately 50% of patients with CPT having NF1. The bowing typically progresses to a fracture that fails to heal (pseudarthrosis) due to abnormal periosteum at the site. It is important to distinguish the direction of bowing: anterolateral bowing is associated with CPT and NF1; posteromedial bowing is associated with calcaneovalgus foot deformity and typically resolves spontaneously (though a leg length discrepancy may persist); and anteromedial bowing is associated with fibular hemimelia. Fibrous dysplasia, osteogenesis imperfecta, achondroplasia, and cleidocranial dysplasia do not classically present with isolated anterolateral tibial bowing and CPT.

Question 6311

Topic: Pediatric Hip

A 12-year-old obese boy presents with 3 weeks of left groin and knee pain. He walks with an antalgic, externally rotated gait. Radiographs confirm a mild, stable slipped capital femoral epiphysis (SCFE). He undergoes in situ single-screw fixation. Which of the following is the most significant risk factor for the development of chondrolysis in this patient?

. Unrecognized joint penetration by the screw
. Severe initial slip angle
. Concomitant prophylactic pinning of the contralateral hip
. Delay in surgical intervention greater than 24 hours
. Use of a fully threaded screw

Correct Answer & Explanation

. Unrecognized joint penetration by the screw

Explanation

Correct Answer: Unrecognized joint penetration by the screwChondrolysis is a devastating complication of SCFE characterized by the rapid destruction of articular cartilage, leading to a stiff, painful hip and joint space narrowing on radiographs. The most significant and well-documented risk factor for chondrolysis following surgical fixation of SCFE is unrecognized intra-articular hardware penetration. To prevent this, surgeons must utilize the "approach-withdraw" technique under fluoroscopy to ensure the screw has not breached the articular surface. While severe slip angle and unstable slips increase the risk of avascular necrosis (AVN), hardware penetration is the primary culprit for chondrolysis. Prophylactic pinning of the contralateral hip does not increase the risk of chondrolysis in the operative hip. Delay in surgery for a stable slip does not inherently cause chondrolysis, though it may allow the slip to progress.

Question 6312

Topic: 4. Pediatrics

A 6-year-old boy with spastic diplegic cerebral palsy presents with progressive bilateral hip subluxation. Radiographs demonstrate a Reimers migration index of 45% bilaterally with significant acetabular dysplasia. He is scheduled to undergo bilateral varus derotational osteotomies (VDRO) and pelvic osteotomies. Which of the following describes the primary biomechanical goal of the pelvic osteotomy in this specific patient population?

. A) To provide isolated anterior coverage of the femoral head
. B) To provide isolated medialization of the hip center of rotation
. C) To provide lateral and posterior coverage of the femoral head
. D) To provide anterior and lateral coverage of the femoral head
. E) To retrovert the acetabulum to compensate for femoral anteversion

Correct Answer & Explanation

. C) To provide lateral and posterior coverage of the femoral head

Explanation

Correct Answer: CIn patients with cerebral palsy (CP), the hip typically subluxates in a posterosuperior direction due to the deforming forces of spastic hip flexors and adductors. Therefore, the acetabular deficiency in CP is predominantly posterosuperior. Pelvic osteotomies utilized in this population, such as the Dega or San Diego osteotomies, are incomplete transiliac osteotomies that hinge on the triradiate cartilage and the symphysis pubis. They are specifically designed to hinge open posteriorly and laterally to provide lateral and posterior coverage of the femoral head. This contrasts with developmental dysplasia of the hip (DDH), where the deficiency is typically anterolateral, and osteotomies like the Salter or Pemberton are used to provide anterior and lateral coverage (Option D). Option A and E are incorrect as they do not address the posterosuperior deficiency. Option B is a secondary benefit of some pelvic osteotomies (like the Chiari) but is not the primary goal of a volume-expanding osteotomy in CP.

Question 6313

Topic: Pediatric Hip

A 12-year-old obese male presents with left knee pain and an antalgic gait for 3 weeks. Examination reveals obligatory external rotation of the left hip with passive flexion. Radiographs confirm a mild, stable slipped capital femoral epiphysis (SCFE) of the left hip. The right hip is radiographically normal. Which of the following is the strongest indication for prophylactic in situ pinning of the contralateral (right) hip?

. A) Patient age of 12 years
. B) Male sex
. C) Body mass index > 95th percentile
. D) Initial slip angle > 30 degrees
. E) Presence of an underlying endocrine disorder

Correct Answer & Explanation

. E) Presence of an underlying endocrine disorder

Explanation

Correct Answer: EProphylactic pinning of the contralateral hip in SCFE is a topic of debate, but there are absolute and relative indications. The strongest indication for prophylactic pinning is the presence of an underlying endocrine disorder (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) or prior radiation therapy. Patients with endocrine disorders have a bilateral involvement rate approaching 100%, compared to the 20-40% bilateral rate in idiopathic cases. Other relative indications for prophylactic pinning include an inability to follow up, young age at presentation (males < 12, females < 10), and open triradiate cartilage. While obesity (Option C) and young age (Option A) increase the risk of a contralateral slip, an endocrine disorder is the most definitive and strongest indication among the choices provided. Slip angle (Option D) and sex (Option B) are not primary determinants for prophylactic contralateral pinning.

Question 6314

Topic: 4. Pediatrics
A 3-year-old boy with a history of idiopathic right clubfoot treated successfully with the Ponseti method and an Achilles tenotomy as an infant presents with a relapse. His parents admit to poor compliance with the foot abduction orthosis over the past year. On examination, he has recurrent equinus and dynamic supination of the foot during the swing phase of gait. Passive correction of the deformity is easily achieved. What is the most appropriate next step in management?
. A) Immediate comprehensive posteromedial release
. B) Repeat serial casting followed by an anterior tibial tendon transfer
. C) Split anterior tibial tendon transfer (SPLATT) only
. D) Calcaneal sliding osteotomy
. E) Talonavicular arthrodesis

Correct Answer & Explanation

. B) Repeat serial casting followed by an anterior tibial tendon transfer

Explanation

Relapse in clubfoot treated with the Ponseti method is most commonly due to noncompliance with the foot abduction orthosis (bracing). In a toddler presenting with a relapsed clubfoot characterized by dynamic supination (due to an overactive tibialis anterior pulling the foot into supination without the counterbalancing pull of the peroneals) and recurrent equinus, the standard treatment is repeat serial casting to regain passive correction, followed by an anterior tibial tendon transfer (ATTT) to the lateral cuneiform. The ATTT removes the deforming supinatory force and converts it into a dorsiflexion force, preventing further relapse. A SPLATT (Option C) is typically reserved for spastic conditions like cerebral palsy or stroke, not idiopathic clubfoot. Comprehensive posteromedial release (Option A) is a historical procedure that leads to a stiff, painful foot in adulthood and is avoided if possible. Bony procedures (Options D and E) are salvage options for rigid, older, or severe syndromic feet, not for a supple relapse in a 3-year-old.

Question 6315

Topic: 4. Pediatrics
An 8-year-old boy presents with a painless limp of 4 months duration. Radiographs of the pelvis demonstrate fragmentation of the right capital femoral epiphysis with lateral subluxation and a "Gage sign". According to the Herring lateral pillar classification, >50% of the lateral pillar height is maintained. Which of the following factors is the most significant predictor of a poor long-term outcome in this patient?
. A) Presence of the Gage sign
. B) Age at onset of 8 years
. C) Male sex
. D) Herring Lateral Pillar Class B
. E) Duration of symptoms

Correct Answer & Explanation

. B) Age at onset of 8 years

Explanation

In Legg-Calvé-Perthes disease, the two most important prognostic factors are the age of onset and the extent of epiphyseal involvement (often measured by the Herring lateral pillar classification). Age at onset > 8 years is a highly significant predictor of a poor outcome because there is less remaining growth potential for the femoral head to remodel into a spherical shape before skeletal maturity. While the "head-at-risk" signs (like the Gage sign, lateral subluxation, calcification lateral to the epiphysis) indicate a higher risk of deformation, age is the overriding prognostic variable. A Herring Lateral Pillar Class B (Option D) in a child > 8 years old actually warrants surgical containment (e.g., femoral or pelvic osteotomy) because the natural history is poor, whereas a child < 8 years with Class B often does well with symptomatic treatment. Male sex (Option C) is more common in Perthes but female sex is actually associated with a worse prognosis because girls mature earlier, leaving even less time for remodeling.

Question 6316

Topic: 4. Pediatrics
A 14-year-old girl sustains an ankle injury while playing soccer. Radiographs and a subsequent CT scan reveal a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. The fracture fragment is displaced 3 mm. Which of the following ligaments is responsible for the avulsion of this specific fracture fragment?
. A) Anterior talofibular ligament
. B) Calcaneofibular ligament
. C) Anterior inferior tibiofibular ligament
. D) Posterior inferior tibiofibular ligament
. E) Deltoid ligament

Correct Answer & Explanation

. C) Anterior inferior tibiofibular ligament

Explanation

The patient has a juvenile Tillaux fracture, which is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. This fracture occurs uniquely in adolescents (typically ages 12-15) because of the asymmetric closure pattern of the distal tibial physis. The physis closes first centrally, then anteromedially, then posteromedially, and finally laterally. When an external rotation force is applied to the foot, the anterior inferior tibiofibular ligament (AITFL) becomes taut. Because the anterolateral physis is the last to close and remains open, the AITFL avulses the anterolateral epiphysis rather than tearing the ligament or causing a syndesmotic injury. The anterior talofibular ligament (Option A) and calcaneofibular ligament (Option B) are lateral ankle ligaments involved in inversion sprains. The posterior inferior tibiofibular ligament (Option D) is involved in Volkmann fractures (posterior malleolus). The deltoid ligament (Option E) is medial.

Question 6317

Topic: 4. Pediatrics
A 2.5-year-old obese girl presents with bilateral bowing of the legs. Standing radiographs reveal a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees bilaterally, with prominent medial metaphyseal beaking of the proximal tibia. She is diagnosed with infantile Blount disease (Langenskiöld stage II). What is the most appropriate initial management?
. A) Observation and reassurance
. B) Knee-ankle-foot orthoses (KAFOs) during weight-bearing
. C) Proximal tibial valgus osteotomy
. D) Guided growth with medial tension band plates
. E) Epiphysiodesis of the lateral proximal tibia

Correct Answer & Explanation

. B) Knee-ankle-foot orthoses (KAFOs) during weight-bearing

Explanation

Infantile Blount disease is characterized by pathologic varus deformity of the proximal tibia due to disordered endochondral ossification of the medial aspect of the proximal tibial physis. A metaphyseal-diaphyseal angle > 16 degrees is highly predictive of progressive Blount disease rather than physiologic bowing. For children under the age of 3 with early-stage infantile Blount disease (Langenskiöld stages I and II), the initial treatment of choice is bracing with Knee-Ankle-Foot Orthoses (KAFOs) worn during weight-bearing activities. Bracing is effective in unloading the medial compartment and allowing the physis to recover. Observation (Option A) is inappropriate given the high Drennan angle and metaphyseal beaking. Surgical intervention, such as a proximal tibial valgus osteotomy (Option C), is indicated if bracing fails, if the child presents after age 4, or if they have advanced Langenskiöld stages (III or higher). Guided growth (Option D) is more commonly used in older children or adolescents with late-onset Blount disease.

Question 6318

Topic: Pediatric Hip

A 4-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 2-week follow-up, the parents report that she is not kicking her left leg as much as her right. On physical examination, the infant lacks active knee extension on the left side, but exhibits normal ankle dorsiflexion and plantar flexion. What is the most likely cause of this physical examination finding?

. Excessive abduction of the hip in the harness
. Excessive flexion of the hip in the harness
. Excessive extension of the hip in the harness
. Inadequate flexion of the hip in the harness
. Excessive adduction of the hip in the harness

Correct Answer & Explanation

. Excessive flexion of the hip in the harness

Explanation

Correct Answer: Excessive flexion of the hip in the harnessThe patient is presenting with a femoral nerve palsy, which is a known complication of Pavlik harness treatment for DDH. Femoral nerve palsy presents as a loss of active knee extension and is caused by hyperflexion of the hip in the harness, which compresses the femoral nerve against the inguinal ligament. If this occurs, the harness should be temporarily removed or adjusted to decrease the amount of hip flexion until nerve function returns. Excessive abduction of the hip (Option A) is associated with avascular necrosis (AVN) of the femoral head, not femoral nerve palsy. Inadequate flexion (Option D) or excessive adduction (Option E) would lead to failure of reduction or posterior dislocation of the hip, rather than a nerve palsy.

Question 6319

Topic: Pediatric Hip

A 12-year-old obese male presents with a 3-week history of left groin pain and an antalgic gait. Radiographs confirm a mild, stable slipped capital femoral epiphysis (SCFE) on the left. The right hip is radiographically normal and asymptomatic. Which of the following patient factors represents the strongest indication for prophylactic in situ pinning of the contralateral (right) hip?

. Patient age of 12 years
. Body Mass Index (BMI) > 95th percentile
. Presence of primary hypothyroidism
. Slip angle of 45 degrees on the affected side
. Male sex

Correct Answer & Explanation

. Presence of primary hypothyroidism

Explanation

Correct Answer: Presence of primary hypothyroidismProphylactic pinning of the contralateral hip in SCFE is a debated topic, but there are clear absolute and relative indications. The strongest indication for prophylactic pinning is the presence of an underlying endocrine disorder, such as hypothyroidism, panhypopituitarism, or renal osteodystrophy, as these patients have a significantly higher risk (up to 100% in some studies) of developing a contralateral slip. Other indications include patients undergoing radiation therapy, and chronologic age less than 10 years (or open triradiate cartilage). While obesity (Option B) and male sex (Option E) are risk factors for SCFE in general, they are not absolute indications for prophylactic pinning on their own. The severity of the slip on the affected side (Option D) does not dictate the need for contralateral prophylaxis.

Question 6320

Topic: Pediatric Lower Extremity

A 2-week-old infant with idiopathic clubfoot is undergoing serial casting using the Ponseti method. The orthopaedic surgeon is preparing to apply the third cast. Which of the following describes the correct sequence of deformity correction in the Ponseti method?

. Cavus, Varus, Adductus, Equinus
. Cavus, Adductus, Varus, Equinus
. Equinus, Cavus, Adductus, Varus
. Adductus, Varus, Cavus, Equinus
. Varus, Cavus, Adductus, Equinus

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

Correct Answer: Cavus, Adductus, Varus, EquinusThe Ponseti method is the gold standard for the treatment of idiopathic clubfoot. The correction follows a specific sequence, easily remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The first step is to elevate the first ray to correct the cavus deformity, which aligns the forefoot with the hindfoot. Subsequent casts gradually abduct the supinated foot around the head of the talus, which simultaneously corrects the adductus and the varus deformities due to the kinematic coupling of the subtalar joint. The equinus deformity is corrected last; attempting to correct it too early can lead to a rocker-bottom foot deformity. If equinus cannot be fully corrected with casting, a percutaneous Achilles tenotomy is performed.

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