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4. Pediatrics MCQs

Practice Set 245 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 4881

Topic: 4. Pediatrics

A 13-year-old obese male presents with left knee pain and a limp. Examination reveals obligate external rotation with passive hip flexion.

A radiograph shows a slipped capital femoral epiphysis. During in situ pinning of this lesion, which of the following represents the optimal starting point for the screw to ensure maximum purchase and minimize joint penetration?

. Anterior aspect of the greater trochanter
. Center of the greater trochanter
. Posterior aspect of the proximal femoral metaphysis
. Anterior aspect of the proximal femoral metaphysis
. Inferior to the lesser trochanter

Correct Answer & Explanation

. Anterior aspect of the greater trochanter

Explanation

In a classic posterior and inferior slip of the capital femoral epiphysis, an anterior starting point on the proximal femoral metaphysis allows the screw to be directed posteriorly to engage the center of the displaced epiphysis. This allows the screw to be perpendicular to the physis, maximizing fixation and minimizing the risk of out-in-out joint penetration.

Question 4882

Topic: 4. Pediatrics
A 3-year-old girl is evaluated for worsening bilateral genu varum. Radiographs show medial metaphyseal beaking and an abnormal Langenskiöld stage II appearance of the proximal medial tibia. What is the primary pathological mechanism of infantile Blount disease?
. Vitamin D deficiency
. Fibrocartilaginous tethering of the medial physis
. Abnormal mechanical loading disrupting enchondral ossification at the medial physis
. Autosomal dominant mutation in FGFR3
. Avascular necrosis of the medial tibial epiphysis

Correct Answer & Explanation

. Abnormal mechanical loading disrupting enchondral ossification at the medial physis

Explanation

Infantile Blount disease (tibia vara) is a developmental disorder characterized by abnormal enchondral ossification of the medial aspect of the proximal tibial physis. It is caused by excessive compressive forces (Heuter-Volkmann principle) in susceptible toddlers (often early walkers and obese), leading to deceleration of growth on the medial side and resulting in progressive varus deformity.

Question 4883

Topic: Pediatric Hip
A 6-week-old female infant is evaluated for developmental dysplasia of the hip. An ultrasound is performed on the right hip. An alpha angle of 55 degrees and a beta angle of 60 degrees is noted on the coronal view. According to the Graf classification, what is the most appropriate management at this stage?
. Observation and repeat ultrasound in 4 weeks
. Immediate Pavlik harness application
. Closed reduction and spica casting
. Open reduction
. Reassurance and discharge from clinic

Correct Answer & Explanation

. Observation and repeat ultrasound in 4 weeks

Explanation

This infant has a Graf Type IIa hip, which is defined by an alpha angle between 50-59 degrees in an infant under 3 months of age. This represents physiologic immaturity, and the vast majority of these hips will resolve spontaneously. The most appropriate management is observation and follow-up ultrasound in 2-4 weeks. A Pavlik harness is indicated for Graf Type IIb (same angles but older than 3 months), III, and IV hips.

Question 4884

Topic: Pediatric Upper Extremity & Spine
A 5-year-old child sustains a completely displaced extension-type Gartland III supracondylar fracture of the humerus. Which of the following clinical findings is most specific for testing the most commonly injured nerve in this fracture pattern?
. Inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger
. Numbness over the dorsal first web space
. Inability to extend the metacarpophalangeal joints of the fingers
. Weakness in spreading the fingers apart against resistance
. Numbness over the volar tip of the little finger

Correct Answer & Explanation

. Inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. It is a pure motor nerve that innervates the FPL, the FDP to the index and middle fingers, and the pronator quadratus. Weakness is evaluated by the 'OK' sign, which corresponds to the inability to actively flex the IP joint of the thumb and the DIP joint of the index finger.

Question 4885

Topic: 4. Pediatrics

A 10-month-old infant is brought to the emergency department by his parents with a swollen and painful left thigh. Radiographs demonstrate a displaced spiral fracture of the femoral diaphysis. There is no clear history of trauma provided. Which of the following is the most appropriate initial step in the management of this patient?

. Immediate open reduction and internal fixation
. Perform a full skeletal survey and consult child protective services
. Application of a Pavlik harness
. Reassure the parents and apply a long leg cast
. Order genetic testing for Osteogenesis Imperfecta

Correct Answer & Explanation

. Immediate open reduction and internal fixation

Explanation

A diaphyseal femur fracture in a non-ambulatory infant (under 1 year of age) is a highly specific marker for non-accidental trauma (child abuse). The most critical initial step is to ensure the child's safety, which requires admission, performing a skeletal survey to identify any other healing fractures, and immediate consultation with child protective services (CPS).

Question 4886

Topic: Pediatric Hip

A 13-year-old obese male presents to the emergency department refusing to bear weight on his right leg after a minor twisting injury. Radiographs reveal a severe slipped capital femoral epiphysis (SCFE). Because he cannot bear weight even with crutches, this is classified as an unstable SCFE. Which of the following complications is significantly more likely in this patient compared to a patient with a stable SCFE?

. Chondrolysis
. Avascular necrosis of the femoral head
. Premature physeal closure
. Femoral acetabular impingement
. Slipped capital femoral epiphysis of the contralateral hip

Correct Answer & Explanation

. Chondrolysis

Explanation

Unstable SCFE is defined by the inability to bear weight on the affected extremity and carries a much higher risk (up to 50%) of developing avascular necrosis (AVN) of the femoral head. Stable SCFE has a very low risk of AVN. Chondrolysis can occur in both, often related to prominent hardware.

Question 4887

Topic: 4. Pediatrics

A 6-year-old boy falls off monkey bars and sustains a displaced supracondylar humerus fracture. Upon arrival, the hand is well-perfused but the radial pulse is not palpable. Following a closed reduction and percutaneous pinning, the hand remains pink and warm with a capillary refill of less than 2 seconds, but the radial pulse remains absent. What is the most appropriate next step in management?

. Immediate vascular surgery consultation for brachial artery exploration
. Removal of the pins and open reduction of the fracture
. Observation and continuous pulse oximetry monitoring of the affected hand
. Immediate performance of an upper extremity CT angiogram
. Administration of intra-arterial vasodilators

Correct Answer & Explanation

. Immediate vascular surgery consultation for brachial artery exploration

Explanation

In a pediatric supracondylar humerus fracture, a "pulseless, pink" hand following closed reduction generally indicates adequate collateral circulation despite probable brachial artery spasm or tethering. The standard of care is close observation and continuous pulse oximetry monitoring rather than immediate surgical exploration.

Question 4888

Topic: Pediatric Hip

A 13-year-old overweight boy presents with a 3-week history of right groin pain and a limp. Examination reveals obligatory external rotation of the hip with passive flexion. What is the most appropriate initial management?

. Strict bed rest and serial radiographs
. Immediate closed reduction and spica casting
. In situ percutaneous pinning of the right hip
. Bilateral prophylactic pinning
. Open reduction and internal fixation through a surgical dislocation approach

Correct Answer & Explanation

. Strict bed rest and serial radiographs

Explanation

The presentation is classic for a Slipped Capital Femoral Epiphysis (SCFE). The standard of care for a stable SCFE is in situ percutaneous pinning with a single cannulated screw in the center of the epiphysis.

Question 4889

Topic: Pediatric Hip

In the evaluation of developmental dysplasia of the hip (DDH) in a 6-month-old infant, which of the following imaging modalities is most appropriate to confirm the diagnosis and assess severity?

. Dynamic ultrasound of the hip
. Anteroposterior (AP) and frog-leg lateral radiographs of the pelvis
. Non-contrast MRI of the pelvis
. Computed tomography (CT) scan of the hips
. Bone scintigraphy

Correct Answer & Explanation

. Dynamic ultrasound of the hip

Explanation

By 4 to 6 months of age, the capital femoral ossific nucleus begins to ossify. This makes AP and frog-leg pelvis radiographs the preferred and reliable imaging modality for evaluating DDH, replacing ultrasound.

Question 4890

Topic: Pediatric Hip

A 13-year-old obese male presents with a 3-week history of left knee pain and an antalgic gait. Examination reveals limited internal rotation of the left hip. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE) on the left. Prophylactic pinning of the contralateral asymptomatic hip is most strongly indicated if the patient has which of the following concomitant conditions?

. Down syndrome
. Endocrine disorder such as hypothyroidism
. Type 1 diabetes mellitus
. Pre-existing avascular necrosis
. Marfan syndrome

Correct Answer & Explanation

. Down syndrome

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but widely recommended in patients with underlying endocrine or metabolic disorders. These conditions, such as hypothyroidism or renal osteodystrophy, significantly increase the risk of bilateral involvement.

Question 4891

Topic: Pediatric Hip

A 13-year-old obese male presents with a 3-week history of left knee pain and an antalgic gait. He is able to bear weight into the examination room with a noticeable limp. Radiographs demonstrate a posterior and inferior displacement of the proximal femoral epiphysis. According to the Loder classification, what is the primary prognostic significance of his ability to bear weight?

. It determines the risk of subsequent chondrolysis
. It dictates the absolute need for a prophylactic contralateral pinning
. It accurately predicts the risk of avascular necrosis (AVN)
. It defines whether an open reduction via a surgical hip dislocation is mandatory
. It strictly correlates with the likelihood of future femoroacetabular impingement (FAI)

Correct Answer & Explanation

. It determines the risk of subsequent chondrolysis

Explanation

The Loder classification is the most clinically relevant system for Slipped Capital Femoral Epiphysis (SCFE) and is based entirely on the patient's ability to bear weight (with or without crutches). A 'stable' SCFE is defined as the patient being able to bear weight, while an 'unstable' SCFE is defined by an inability to bear weight. The primary prognostic importance of this classification is the risk of avascular necrosis (AVN). Stable slips have a very low risk of AVN (<10%), whereas unstable slips have a high rate of AVN, historically reported up to 50%.

Question 4892

Topic: Pediatric Hip
A 6-year-old boy presents with a painless limp and restricted hip abduction and internal rotation. Radiographs reveal fragmentation of the capital femoral epiphysis with a prominent subchondral lucency (crescent sign). According to the lateral pillar (Herring) classification, what specific radiographic criterion defines a Group B classification?
. No radiolucency in the lateral pillar and normal height
. >50% of the lateral pillar height is maintained compared to the contralateral side
. <50% of the lateral pillar height is maintained compared to the contralateral side
. Extrusion of the epiphysis >20% beyond the lateral margin of the acetabulum
. Central pillar depression with entirely intact medial and lateral pillars

Correct Answer & Explanation

. >50% of the lateral pillar height is maintained compared to the contralateral side

Explanation

Legg-Calvé-Perthes disease is characterized by idiopathic avascular necrosis of the proximal femoral epiphysis in children. The Herring (Lateral Pillar) classification is assessed during the fragmentation phase on AP radiographs and is highly prognostic. Group A: No involvement of the lateral pillar (100% height maintained). Group B: >50% of lateral pillar height is maintained. Group C: <50% of lateral pillar height is maintained. Group B/C border: Exactly 50% height maintained. Patients >8 years old at onset with Group B, and all patients with Group C, generally have a poorer prognosis and are more likely to require surgical containment.

Question 4893

Topic: Pediatric Lower Extremity

The Ponseti method is the internationally recognized gold standard for the conservative management of idiopathic congenital talipes equinovarus (clubfoot). During the serial casting process, the complex triplanar deformities are sequentially corrected. Which of the following represents the correct order of deformity correction according to the strict Ponseti protocol?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method requires meticulous serial casting that strictly follows a specific order of correction to accommodate the specific pathoanatomy of the talocalcaneonavicular joint block. The mnemonic CAVE dictates the correct sequence: First, the Cavus is corrected (by elevating the first ray to align the forefoot with the hindfoot). Second, the Adductus and third, the Varus, are corrected simultaneously by abducting the midfoot around the head of the talus. Finally, the Equinus is corrected last (often requiring a percutaneous Achilles tenotomy to achieve 15-20 degrees of dorsiflexion before the final cast is placed). Correcting equinus prematurely leads to a 'rocker-bottom' foot deformity.

Question 4894

Topic: 4. Pediatrics

Achondroplasia is the most common form of skeletal dysplasia leading to disproportionate short stature, inherited in an autosomal dominant pattern. At the cellular level within the growth plate (physis), the primary pathologic defect is best described by which of the following?

. Hyperproliferation of chondrocytes in the reserve zone
. Decreased proliferation and hypertrophy of chondrocytes in the proliferative and hypertrophic zones
. Excessive mineralization of the primary spongiosa
. Defective type X collagen secretion by hypertrophic chondrocytes
. Failure of osteoclast-mediated resorption of the secondary spongiosa

Correct Answer & Explanation

. Hyperproliferation of chondrocytes in the reserve zone

Explanation

Achondroplasia is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. FGFR3 normally functions as a negative regulator of bone growth. The mutation leads to constitutional activation of the receptor, which severely inhibits chondrocyte proliferation and hypertrophy in the physis, resulting in stunted endochondral ossification.

Question 4895

Topic: Pediatric Hip

Which of the following represents an absolute indication for prophylactic in situ pinning of the contralateral hip in a pediatric patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. Age greater than 14 years at presentation
. Concomitant renal osteodystrophy or endocrine disorder
. Female gender
. African American race
. Obesity greater than the 95th percentile for age

Correct Answer & Explanation

. Age greater than 14 years at presentation

Explanation

Prophylactic pinning of the contralateral hip in SCFE is generally indicated in patients with a high risk of subsequent bilateral involvement. Absolute indications typically include endocrine or systemic metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) and prior pelvic radiation. Relative indications include very young presentation (age < 10 years).

Question 4896

Topic: Pediatric Lower Extremity

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

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method requires sequential correction of the clubfoot deformities in a specific order: Cavus (corrected by elevating the first ray), Adductus, Varus, and finally Equinus (often requiring a percutaneous Achilles tenotomy). This sequence is commonly remembered by the mnemonic CAVE.

Question 4897

Topic: Pediatric Hip

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a routine follow-up, the mother notes the child is no longer actively extending her knee on the treated side. What is the most likely iatrogenic cause of this physical finding?

. Obturator nerve palsy due to excessive abduction
. Femoral nerve palsy due to excessive hip flexion
. Sciatic nerve palsy due to excessive hip extension
. Avascular necrosis of the femoral head
. Slipped capital femoral epiphysis

Correct Answer & Explanation

. Obturator nerve palsy due to excessive abduction

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment and is caused by excessive hip flexion, which compresses the femoral nerve against the inguinal ligament or the rim of the pelvis. It presents as diminished quadriceps activity and decreased knee extension. Treatment involves loosening the anterior straps or removing the harness temporarily.

Question 4898

Topic: Pediatric Hip

A 6-month-old female with developmental dysplasia of the hip (DDH) has been managed in a Pavlik harness for 4 weeks. Serial ultrasound imaging today demonstrates persistent dislocation of the left hip. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 4 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld splint)
. Abandon the harness and proceed to closed reduction and spica casting
. Perform an immediate open reduction
. Adjust the Pavlik harness to increase hip flexion past 120 degrees

Correct Answer & Explanation

. Continue the Pavlik harness for an additional 4 weeks

Explanation

Failure of a Pavlik harness to achieve reduction after 3 to 4 weeks warrants its removal to prevent 'Pavlik harness disease' (posterior acetabular wear and worsening dysplasia). The next appropriate step is closed reduction and application of a hip spica cast.

Question 4899

Topic: Pediatric Lower Extremity

A newborn is diagnosed with idiopathic clubfoot (talipes equinovarus) and is started on the Ponseti method of serial casting. What is the correct sequence of deformity correction, and which deformity must be addressed first?

. Equinus is corrected first by percutaneous tenotomy
. Hindfoot varus is corrected first by everting the heel
. Forefoot adduction is corrected first by abducting the midfoot
. Cavus is corrected first by elevating the first ray
. Tibial torsion is corrected first by derotation

Correct Answer & Explanation

. Equinus is corrected first by percutaneous tenotomy

Explanation

In the Ponseti method (C-A-V-E sequence), the Cavus deformity must be corrected first by supinating the forefoot and elevating the first ray. This aligns the forefoot with the hindfoot, unlocking the midtarsal joint for subsequent abduction.

Question 4900

Topic: Pediatric Hip

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The mother notes that the child has stopped actively extending the knee on the affected side. Hyperflexion of the hip in the harness is suspected. Which nerve is most likely compressed?

. Sciatic nerve
. Femoral nerve
. Obturator nerve
. Superior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament. This results in a transient femoral nerve palsy, presenting clinically as a loss of active knee extension.

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