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4. Pediatrics MCQs

Practice Set 213 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 4241

Topic: Pediatric Hip

A 10-week-old female infant with a completely dislocated, reducible developmental dysplasia of the hip (DDH) has been treated with a Pavlik harness for 2 weeks. The mother notes the child is no longer actively kicking her left leg, specifically lacking active knee extension. What is the most appropriate next step in management?

. Continue the harness and add physical therapy
. Immediately discontinue the Pavlik harness and observe for neurologic recovery
. Adjust the anterior straps to increase hip flexion past 120 degrees
. Switch to a rigid hip abduction orthosis (Rhino Cruiser)
. Proceed to closed reduction and spica casting under anesthesia

Correct Answer & Explanation

. Immediately discontinue the Pavlik harness and observe for neurologic recovery

Explanation

The clinical picture describes a femoral nerve palsy, a known complication of hyperflexion in a Pavlik harness. If a femoral nerve palsy develops, the harness must be discontinued immediately to allow for neurologic recovery, which typically resolves in days to weeks. Continuing the harness or increasing flexion can worsen the nerve injury.

Question 4242

Topic: 4. Pediatrics

According to the Gross Motor Function Classification System (GMFCS), a patient with cerebral palsy is classified as Level V. At what approximate frequency should routine radiographic hip surveillance be conducted for this patient after the age of 2 years to monitor for hip displacement?

. Once at age 5 years, then only if symptomatic
. Every 5 years until skeletal maturity
. Every 2-3 years until skeletal maturity
. Every 6-12 months until skeletal maturity
. Only if the patient develops pain or gait deterioration

Correct Answer & Explanation

. Every 6-12 months until skeletal maturity

Explanation

Patients with GMFCS level V cerebral palsy have a nearly 90% risk of hip displacement. International hip surveillance guidelines recommend that these non-ambulatory, severely involved patients undergo AP pelvic radiographs every 6 to 12 months after 2 years of age until skeletal maturity to monitor Reimers' migration index and intervene before severe dislocation occurs.

Question 4243

Topic: Pediatric Hip
An 8-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Radiographs demonstrate fragmentation of the femoral head with more than 50% loss of height of the lateral pillar. According to the Herring classification, what is the assigned group and expected prognosis without intervention?
. Group A; Excellent prognosis without surgery
. Group B; Good prognosis regardless of age
. Group B/C border; Variable prognosis depending on range of motion
. Group C; Poor prognosis, likely leading to aspherical incongruency
. Group D; Rapidly progressive destructive disease requiring total hip arthroplasty

Correct Answer & Explanation

. Group C; Poor prognosis, likely leading to aspherical incongruency

Explanation

The Herring lateral pillar classification divides LCPD into Groups A (no lateral pillar involvement), B (>50% lateral pillar height maintained), B/C border, and C (<50% lateral pillar height maintained). Group C signifies severe collapse and carries a poor prognosis with a high likelihood of developing a flattened, incongruous femoral head, especially in children older than 8 years.

Question 4244

Topic: 4. Pediatrics
A 14-year-old adolescent sustains a triplane fracture of the distal tibia following an external rotation injury. By definition, a classic triplane fracture involves a combination of fracture planes. Which Salter-Harris classification does this complex fracture pattern biologically represent?
. Salter-Harris I
. Salter-Harris II
. Salter-Harris III
. Salter-Harris IV
. Salter-Harris V

Correct Answer & Explanation

. Salter-Harris IV

Explanation

A classic triplane fracture extends in the sagittal plane through the epiphysis, the axial plane through the physis, and the coronal plane through the posterior metaphysis. Because the fracture crosses from the metaphysis, through the physis, and exits the epiphysis into the joint space, it is biologically equivalent to a Salter-Harris IV fracture.

Question 4245

Topic: 4. Pediatrics

A 2-year-old boy presents with short stature, frontal bossing, and rhizomelic shortening of the limbs. Radiographs of the spine show progressive narrowing of the interpedicular distances from the upper to the lower lumbar spine. What genetic mutation is responsible for this condition?

. COL1A1 loss-of-function mutation
. FGFR3 gain-of-function mutation
. COMP gene mutation
. RUNX2 haploinsufficiency
. FBN1 mutation

Correct Answer & Explanation

. FGFR3 gain-of-function mutation

Explanation

The clinical and radiographic presentation is classic for achondroplasia. Achondroplasia is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene on chromosome 4p, which abnormally inhibits chondrocyte proliferation in the proliferative zone of the physis, leading to rhizomelic dwarfism.

Question 4246

Topic: 4. Pediatrics

A 4-month-old infant with a history of shoulder dystocia at birth has an unresolved Erb-Duchenne palsy (C5-C6). The arm is held in internal rotation, adduction, and pronation. According to current pediatric orthopedic guidelines, lack of clinically detectable recovery of which specific muscle by age 3 to 6 months is the primary indication for primary nerve microsurgery?

. Triceps brachii
. Deltoid
. Biceps brachii
. Flexor carpi ulnaris
. Supinator

Correct Answer & Explanation

. Biceps brachii

Explanation

In neonatal brachial plexus palsy (Erb's palsy), the recovery of the biceps muscle is the most critical prognostic indicator. Lack of clinically apparent biceps function (elbow flexion against gravity) by 3 to 6 months of age is the universally accepted indication to proceed with microsurgical nerve exploration and reconstruction to optimize long-term upper extremity function.

Question 4247

Topic: Pediatric Hip

A 12-year-old boy presents with left-sided groin pain and an obligatory external rotation of the hip during active flexion. Radiographs confirm a left-sided Slipped Capital Femoral Epiphysis (SCFE). Which of the following patient factors represents the strongest indication for prophylactic in situ pinning of the contralateral, asymptomatic right hip?

. Obesity with a BMI > 95th percentile
. Male gender
. African American ethnicity
. Presence of an underlying endocrinopathy, such as hypothyroidism
. Age of onset greater than 14 years

Correct Answer & Explanation

. Presence of an underlying endocrinopathy, such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended in patients with endocrine or metabolic disorders (e.g., hypothyroidism, panhypopituitarism, renal osteodystrophy) or previous radiation therapy, as these conditions carry a bilateral involvement risk approaching 100%. While obesity is a risk factor for SCFE, it is not an absolute indication for prophylactic contralateral pinning without other high-risk features.

Question 4248

Topic: Pediatric Hip
An 8.5-year-old boy is diagnosed with Legg-Calvé-Perthes disease. AP and frog-leg lateral pelvic radiographs demonstrate exactly 50% maintenance of the lateral pillar height on the affected side. According to the prospective multicenter Herring study, what is the most appropriate management for this patient to optimize the long-term sphericity of the femoral head?
. Symptomatic management with non-weight-bearing crutches
. A-frame abduction bracing
. Proximal femoral varus osteotomy or pelvic osteotomy
. Core decompression of the femoral head
. Hinged external fixation (arthrodiastasis)

Correct Answer & Explanation

. Proximal femoral varus osteotomy or pelvic osteotomy

Explanation

The patient has Herring Lateral Pillar Group B or B/C border disease. The prospective Herring multicenter study demonstrated that for children older than 8 years of age at the time of onset with Lateral Pillar Group B or B/C border disease, surgical containment (such as a proximal femoral varus osteotomy or pelvic osteotomy) yields significantly better outcomes compared to nonoperative treatment. Children under 8 with Group B do well regardless of treatment, and Group C children do poorly regardless of treatment.

Question 4249

Topic: 4. Pediatrics

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the left hip. Two weeks after the initiation of treatment, the mother notes that the infant has stopped kicking her left leg. On examination, the left knee is held in a resting extended position, and the infant does not actively flex the hip or extend the knee. What is the most likely etiology of this complication?

. Avascular necrosis of the femoral head due to excessive abduction
. Femoral nerve palsy due to excessive hip flexion
. Sciatic nerve palsy due to excessive hip flexion
. Obturator nerve palsy due to excessive hip abduction
. Transient synovitis of the hip due to strap friction

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hip flexion

Explanation

The clinical picture describes a femoral nerve palsy, which presents as decreased active quadriceps function (lack of active knee extension). In the setting of a Pavlik harness, this is caused by hyperflexion of the hips, leading to compression of the femoral nerve against the inguinal ligament. Management involves temporarily discontinuing the harness or reducing the degree of hip flexion until nerve function fully recovers. Excessive abduction, by contrast, increases the risk of avascular necrosis (AVN).

Question 4250

Topic: 4. Pediatrics
A 13-year-old girl sustains an external rotation twisting injury to her ankle. Radiographs reveal a Salter-Harris type III fracture of the anterolateral aspect of the distal tibial epiphysis. Avulsion of this fragment is caused by tension from which of the following ligamentous structures?
. Anterior talofibular ligament (ATFL)
. Calcaneofibular ligament (CFL)
. Anterior inferior tibiofibular ligament (AITFL)
. Posterior inferior tibiofibular ligament (PITFL)
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament (AITFL)

Explanation

This is a juvenile Tillaux fracture, which is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. The distal tibial physis closes in a specific pattern: first centrally, then anteromedially, then posteromedially, and finally laterally. Because the anterolateral physis is the last to fuse, external rotation forces cause the anterior inferior tibiofibular ligament (AITFL) to avulse this epiphyseal fragment.

Question 4251

Topic: 4. Pediatrics

A 6-year-old child with spastic diplegic cerebral palsy is evaluated during a routine surveillance visit. An AP pelvis radiograph demonstrates a Reimers Migration Percentage of 45% bilaterally. The acetabular index is 32 degrees. The hips are clinically subluxated but reducible. What is the most definitive surgical management to provide stable, long-term hip containment?

. Bilateral adductor and iliopsoas tenotomies only
. Bilateral proximal femoral varus derotation osteotomies (VDRO) with pelvic osteotomies
. Bilateral proximal femoral valgus osteotomies
. Bilateral total hip arthroplasties
. Botulinum toxin type A injections to the adductors and hamstrings

Correct Answer & Explanation

. Bilateral proximal femoral varus derotation osteotomies (VDRO) with pelvic osteotomies

Explanation

In children with cerebral palsy, a Reimers Migration Percentage (MP) greater than 40-50% with an increased acetabular index indicates a significantly subluxated hip that requires bony reconstruction. Soft tissue releases alone are insufficient at this stage. The standard of care is a proximal femoral varus derotation osteotomy (VDRO) to correct excessive valgus and anteversion, combined with a pelvic osteotomy (e.g., Dega or San Diego) to correct acetabular dysplasia.

Question 4252

Topic: 4. Pediatrics

A 6-year-old child presents with a painful, loud snapping sound in the lateral compartment of the knee during extension. MRI demonstrates a thickened, discoid lateral meniscus that has pulled into the intercondylar notch. Arthroscopic evaluation reveals the meniscus is hypermobile. Which specific anatomical feature defines the 'Wrisberg variant' of a discoid meniscus?

. Absence of the anterior horn attachment to the tibia
. Absence of the posterior meniscotibial (coronary) ligament
. Absence of the meniscofemoral ligament of Wrisberg
. Anomalous insertion of the popliteus tendon into the lateral meniscus
. Presence of a complete transverse intermeniscal ligament

Correct Answer & Explanation

. Absence of the posterior meniscotibial (coronary) ligament

Explanation

The Wrisberg variant of a discoid lateral meniscus is characterized by the absence of the posterior meniscotibial (coronary) ligament attachments. Its only posterior attachment is the meniscofemoral ligament of Wrisberg. During knee extension, the pull of this ligament causes the hypermobile meniscus to snap into the intercondylar notch, causing a symptomatic 'clunk' or 'snap'.

Question 4253

Topic: 4. Pediatrics
A 4-year-old child with Osteogenesis Imperfecta Type III is treated with cyclical intravenous pamidronate therapy to decrease fracture frequency. Which of the following radiographic findings on a long-bone radiograph provides objective evidence of the patient's compliance with this specific pharmacological therapy?
. Erlenmeyer flask deformities of the distal femur
. Multiple dense transverse metaphyseal lines (zebra lines)
. Widening of the physis with metaphyseal fraying
. Cortical thickening with a 'tram-track' appearance
. Resolution of wormian bones in the skull

Correct Answer & Explanation

. Multiple dense transverse metaphyseal lines (zebra lines)

Explanation

Intravenous bisphosphonates (like pamidronate) used in Osteogenesis Imperfecta inhibit osteoclast-mediated bone resorption. Administered in cycles, they temporarily halt the normal metaphyseal modeling process, resulting in dense transverse bands of sclerotic bone parallel to the physis, often referred to as 'zebra lines'. These serve as a radiographic marker of prior treatment cycles.

Question 4254

Topic: 4. Pediatrics
A 4-year-old obese male presents with severe, progressive bilateral infantile tibia vara. Radiographs reveal a sharp step-off and depression of the medial tibial metaphysis. According to the Langenskiöld classification, this child is classified as having Stage III disease. What is the most appropriate definitive management?
. Observation and yearly radiographic follow-up
. Immediate fitting for bilateral knee-ankle-foot orthoses (KAFOs)
. Bilateral proximal tibial valgus osteotomies
. Resection of the medial physeal bar and fat graft interposition
. Epiphysiodesis of the lateral proximal tibia and distal femur

Correct Answer & Explanation

. Bilateral proximal tibial valgus osteotomies

Explanation

In infantile Blount's disease (tibia vara), brace treatment (KAFO) is only effective for children under the age of 3 with Langenskiöld Stage I or II disease. Once a child reaches 4 years of age or progresses to Langenskiöld Stage III (which involves a step-off in the metaphysis), conservative management is universally unsuccessful. The standard of care is a proximal tibial valgus osteotomy (often with derotation) before permanent physeal damage occurs.

Question 4255

Topic: 4. Pediatrics

A 10-month-old, non-ambulatory infant is brought to the emergency department for irritability. Radiographs reveal an isolated, displaced spiral fracture of the left femoral shaft. The parents state the infant fell off a low sofa onto a carpeted floor. What is the most critical next step in the clinical management of this patient?

. Immediate closed reduction and placement of a spica cast and discharge home
. Surgical stabilization with flexible intramedullary nails
. Admission, comprehensive skeletal survey, and consultation with Child Protective Services
. Obtain an MRI of the lower extremities to rule out pathologic fracture
. Application of a Pavlik harness for 6 weeks

Correct Answer & Explanation

. Admission, comprehensive skeletal survey, and consultation with Child Protective Services

Explanation

Any femoral shaft fracture in a non-ambulatory infant is highly suspicious for non-accidental trauma (child abuse), regardless of the fracture pattern (spiral or transverse). A low-energy fall from a sofa cannot generate the force required to break an infant's femur. The paramount next step is hospital admission, performing a complete skeletal survey, and consulting Child Protective Services to ensure the child's safety.

Question 4256

Topic: Pediatric Upper Extremity & Spine

A 35-year-old male presents with progressive intrinsic muscle weakness in his right hand and numbness involving the ring and small fingers. He recalls sustaining an elbow injury at age 5 that was treated non-operatively in a cast. Physical examination reveals a prominent cubitus valgus deformity of the right elbow. What was the most likely pediatric elbow injury this patient sustained?

. Extension-type supracondylar humerus fracture
. Medial epicondyle fracture
. Radial neck fracture
. Lateral condyle fracture of the humerus
. Monteggia fracture-dislocation

Correct Answer & Explanation

. Lateral condyle fracture of the humerus

Explanation

The classic presentation of a missed or non-united lateral condyle fracture of the humerus in childhood is the gradual development of a cubitus valgus deformity over years. This valgus stretching of the ulnar nerve behind the medial epicondyle leads to a 'tardy ulnar nerve palsy' decades later, manifesting as intrinsic hand weakness and sensory changes in the ulnar nerve distribution.

Question 4257

Topic: 4. Pediatrics
A 3-year-old child presents with an anterolateral bow of the right tibia and a distinct mid-diaphyseal pseudarthrosis. Examination reveals multiple café-au-lait macules on the trunk. This underlying genetic syndrome is caused by a mutation in a gene that encodes a protein responsible for downregulating which of the following cellular signaling pathways?
. Wnt/beta-catenin pathway
. RAS/MAPK signaling pathway
. Fibroblast growth factor receptor 3 (FGFR3) pathway
. Transforming growth factor-beta (TGF-b) pathway
. PI3K/AKT/mTOR pathway

Correct Answer & Explanation

. RAS/MAPK signaling pathway

Explanation

The patient has congenital pseudarthrosis of the tibia (CPT) with classic signs of Neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant condition caused by a mutation in the NF1 gene on chromosome 17. The gene encodes neurofibromin, which is a GTPase-activating protein that normally downregulates the RAS/MAPK signaling pathway. Loss of neurofibromin leads to hyperactive RAS signaling, contributing to tumor formation and dysplastic bone.

Question 4258

Topic: 4. Pediatrics

A 14-year-old elite adolescent baseball pitcher presents with vague, insidious shoulder pain that is maximal during the late cocking and early acceleration phases of throwing. An AP radiograph of the shoulder with the arm in external rotation reveals widening of the proximal humeral physis with adjacent metaphyseal sclerosis. What is the most appropriate initial management?

. Arthroscopic labral repair
. Cessation of all throwing activities for a minimum of 3 months
. Immediate physical therapy focused on internal rotation stretching only
. Percutaneous in situ pinning of the proximal humeral physis
. Diagnostic ultrasound and subacromial corticosteroid injection

Correct Answer & Explanation

. Cessation of all throwing activities for a minimum of 3 months

Explanation

This patient has 'Little League Shoulder', which is a stress fracture (epiphysiolysis) of the proximal humeral physis due to repetitive rotational torque from throwing. The pathognomonic radiographic sign is widening and irregularity of the proximal humeral physis. The definitive treatment is absolute rest from throwing, typically for 3 months, followed by a gradual return-to-throwing program.

Question 4259

Topic: 4. Pediatrics

A newborn infant presents with a congenital lower extremity deformity characterized by marked shortening of the right leg, a dimple over the anterior tibia, equinovalgus foot deformity, and the absence of the lateral two digits of the right foot. Radiographs confirm the complete absence of the fibula. Which of the following knee anomalies is almost universally present in this condition?

. Complete absence of the patella
. Bipartite medial meniscus
. Anterior cruciate ligament (ACL) deficiency or absence
. Congenital dislocation of the proximal tibiofibular joint
. Osteochondritis dissecans of the lateral femoral condyle

Correct Answer & Explanation

. Anterior cruciate ligament (ACL) deficiency or absence

Explanation

Fibular hemimelia is the most common long-bone deficiency. It is associated with a spectrum of anomalies along the lateral column of the lower extremity, including anteromedial tibial bowing with a skin dimple, ball-and-socket ankle joint, tarsal coalitions, and absent lateral rays. In the knee, anterior cruciate ligament (ACL) absence or profound hypoplasia is almost universally present, often leading to knee instability.

Question 4260

Topic: 4. Pediatrics

A 3-year-old child presents with massive, asymmetric overgrowth of the index and middle fingers of the right hand. The affected digits are enlarged in both length and girth, and are becoming progressively stiff and deviated. A biopsy of the subcutaneous tissue shows massive fibrofatty infiltration of the digital nerves. This condition, known as macrodactyly or macrodystrophia lipomatosa, is driven by a somatic mosaic mutation in which of the following genes?

. FGFR3
. PIK3CA
. COL1A1
. RUNX2
. SHOX

Correct Answer & Explanation

. PIK3CA

Explanation

Macrodactyly (macrodystrophia lipomatosa) is characterized by fibrofatty enlargement of a nerve territory (most commonly the median nerve in the hand) leading to asymmetric digital overgrowth. It falls under the umbrella of PIK3CA-related overgrowth spectrum (PROS). The genetic basis is a somatic gain-of-function mosaic mutation in the PIK3CA gene, which upregulates the PI3K/AKT/mTOR pathway, causing excessive cellular growth.

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