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4. Pediatrics MCQs

Practice Set 138 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 2741

Topic: Pediatric Hip

A 3-year-old girl is diagnosed with a neglected, completely dislocated unilateral developmental dysplasia of the hip. She is scheduled for an open reduction and pelvic osteotomy. What is the primary biomechanical rationale for performing a concurrent femoral shortening osteotomy in this patient?

. To correct excessive femoral anteversion
. To stimulate rapid acetabular remodeling
. To reduce tension on the soft tissues and minimize the risk of avascular necrosis
. To overcorrect leg lengths postoperatively
. To redirect the femoral head posteriorly into the true acetabulum

Correct Answer & Explanation

. To correct excessive femoral anteversion

Explanation

In older children (typically over 2-3 years) with untreated DDH, a femoral shortening osteotomy is often necessary during open reduction. Shortening the femur relieves soft-tissue tension across the joint, significantly reducing the risk of avascular necrosis.

Question 2742

Topic: Pediatric Hip

A 14-year-old girl presents with progressive groin pain and marked stiffness 8 months after undergoing an uncomplicated in situ pinning for a stable slipped capital femoral epiphysis. Radiographs reveal diffuse narrowing of the hip joint space with preservation of femoral head sphericity. What is the most likely diagnosis?

. Avascular necrosis
. Septic arthritis
. Chondrolysis
. Implant prominence into the joint
. Femoroacetabular impingement

Correct Answer & Explanation

. Avascular necrosis

Explanation

Chondrolysis is characterized by diffuse joint space narrowing and severe stiffness following SCFE treatment, with the femoral head typically remaining spherical. Risk factors include severe slips, spica casting, and unrecognized intra-articular hardware penetration.

Question 2743

Topic: 4. Pediatrics

When interpreting an anteroposterior pelvic radiograph of a 6-month-old infant for developmental dysplasia of the hip, the normal position of the proximal femoral ossific nucleus (or its expected location) should be in which quadrant formed by Hilgenreiner's and Perkin's lines?

. Superomedial
. Superolateral
. Inferomedial
. Inferolateral
. Central to the triradiate cartilage

Correct Answer & Explanation

. Superomedial

Explanation

Hilgenreiner's line is drawn horizontally through the triradiate cartilages, and Perkin's line is drawn perpendicular to it at the lateral margin of the acetabulum. The normal femoral head must reside in the inferomedial quadrant.

Question 2744

Topic: 4. Pediatrics

When performing in situ pinning for a stable slipped capital femoral epiphysis using a single fully threaded cannulated screw, what is the optimal position of the screw within the epiphysis to achieve maximal biomechanical stability and reduce the risk of joint penetration?

. Anterior on the AP plane and superior on the lateral plane
. Anterior on the AP plane and inferior on the lateral plane
. Posterior on the AP plane and superior on the lateral plane
. Central on both the AP and lateral planes
. Central on the AP plane and posterior on the lateral plane

Correct Answer & Explanation

. Anterior on the AP plane and superior on the lateral plane

Explanation

The ideal trajectory for an in situ screw in a SCFE is perpendicular to the physis, placing the threads central in both the AP and lateral radiographic views. This center-center position provides maximum hold in the epiphysis while limiting the "in-out-in" phenomenon.

Question 2745

Topic: Pediatric Hip

An ultrasound is performed on a 4-week-old female infant to evaluate for developmental dysplasia of the hip. According to the Graf classification, a normal, mature hip (Type 1) is defined by which of the following sonographic measurements?

. Alpha angle greater than 60 degrees
. Alpha angle less than 50 degrees
. Beta angle greater than 77 degrees
. Alpha angle between 50 and 59 degrees
. Beta angle less than 43 degrees

Correct Answer & Explanation

. Alpha angle greater than 60 degrees

Explanation

In the Graf ultrasound classification, the alpha angle measures the concavity of the bony acetabular roof. An alpha angle greater than 60 degrees indicates a normal, mature hip (Type 1).

Question 2746

Topic: 4. Pediatrics

Figure 3a shows the preoperative radiograph of a 5-year-old girl who achieved complete correction with valgus osteotomies. Figure 3b shows a radiograph obtained 2 years later. What is the cause of the recurrent deformity on the right side?

. Inadequate restoration of the weight-bearing axis
. Partial growth arrest of the medial tibial physis
. Age older than 3 years
. Obesity (greater than the 95th percentile)
. A metaphyseal-diaphyseal angle of greater than 20 degrees

Correct Answer & Explanation

. Inadequate restoration of the weight-bearing axis

Explanation

Although inadequate correction, obesity, patient age of older than 5 years and an increased metaphyseal-diaphyseal angle are all associated with a poorer outcome, the radiographs show a growth arrest of the medial tibial physis. If not recognized and treated with early surgery, progressive genu varum will occur with continued growth of the lateral physis. In addition to repeat osteotomy, options for treating the arrest include physeal bar resection or, as necessary, completion of the growth arrest by epiphyseodesis of the lateral physes, followed by a limb equalization procedure at a later date. Brooks WC, Gross RH: Genu varum in children: Diagnosis and treatment. J Am Acad Orthop Surg 1995;3:326-335. Herring JA: Tachdjian's Pediatric Orthopedics, ed 4. Philadelphia, PA, WB Saunders, 2002, pp 840-950.

Question 2747

Topic: Pediatric Hip

A 3-month-old girl with Developmental Dysplasia of the Hip (DDH) is treated with a Pavlik harness. At her two-week follow-up, the mother reports that the infant is no longer kicking her right leg as much. On examination, the infant demonstrates decreased active knee extension on the right side. What is the most likely cause of this finding?

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

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hip flexion

Explanation

Hyperflexion of the hips in a Pavlik harness can cause compression of the femoral nerve against the inguinal ligament, leading to a femoral nerve palsy. This presents as decreased active extension of the knee (quadriceps weakness). The treatment is to decrease the amount of flexion or temporarily discontinue the harness until nerve function returns. Avascular necrosis is typically caused by excessive abduction.

Question 2748

Topic: Pediatric Hip

A 13-year-old obese boy undergoes in situ single screw fixation for a stable mild slipped capital femoral epiphysis (SCFE) of the left hip. Nine months later, he returns complaining of progressive left hip pain, severe stiffness, and an inability to participate in sports. Radiographs reveal diffuse joint space narrowing of the left hip and subchondral irregularities, with the screw threads completely within the femoral head. What is the most likely diagnosis?

. Avascular necrosis of the femoral head
. Chondrolysis
. Implant failure
. Septic arthritis
. Contralateral SCFE

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Chondrolysis is a devastating complication of SCFE characterized by acute or insidious onset of pain, marked stiffness, and diffuse joint space narrowing on radiographs. Although hardware penetration into the joint is a known risk factor, chondrolysis can occur even with properly placed implants or unoperated cases. Avascular necrosis typically presents with subchondral collapse, sclerosis, or segmental changes rather than global joint space narrowing.

Question 2749

Topic: Pediatric Upper Extremity & Spine

A 12-year-old premenarcheal girl presents for evaluation of a spinal deformity. She is Risser 0. Standing posteroanterior and lateral radiographs of the spine reveal a right thoracic curve of 36 degrees and normal sagittal alignment. Which of the following is the most appropriate treatment recommendation?

. Observation with repeat radiographs in 6 months
. Full-time wear of a thoracolumbosacral orthosis (TLSO)
. Nighttime bending brace only
. Posterior spinal fusion with instrumentation
. Anterior vertebral body tethering

Correct Answer & Explanation

. Observation with repeat radiographs in 6 months

Explanation

Indications for bracing in adolescent idiopathic scoliosis (AIS) include a curve magnitude between 25 and 45 degrees in a skeletally immature patient (Risser 0-2, premenarcheal or less than 1 year postmenarcheal). A full-time TLSO has been shown in multicenter randomized trials (e.g., BrAIST) to significantly decrease the progression of curves to the surgical threshold.

Question 2750

Topic: Pediatric Lower Extremity

A 4-week-old infant is undergoing treatment for an idiopathic right clubfoot using the Ponseti method. After four sequential casts, the forefoot is abducted to 60 degrees, and the heel is in valgus. However, the ankle can only be dorsiflexed to neutral. What is the most appropriate next step in management?

. Apply a fifth cast in maximal dorsiflexion and observe
. Perform an open tendo-Achilles lengthening
. Perform a percutaneous Achilles tenotomy followed by casting
. Perform a tibialis anterior tendon transfer
. Transition to a Denis Browne bar and shoes immediately

Correct Answer & Explanation

. Apply a fifth cast in maximal dorsiflexion and observe

Explanation

In the Ponseti method, serial casting corrects cavus, adductus, and varus deformities first. Once the forefoot is abducted to roughly 60 degrees and the hindfoot varus is corrected to valgus, the equinus is addressed. If there is less than 15 degrees of ankle dorsiflexion at this stage (which occurs in about 80% of patients), a percutaneous Achilles tenotomy is indicated, followed by a final cast in hyperdorsiflexion and abduction for 3 weeks.

Question 2751

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy sustains a supracondylar fracture of the humerus. Radiographs demonstrate a Gartland Type III fracture with posteromedial displacement of the distal fragment. Which of the following neurologic deficits is most likely to be present?
. Weakness of thumb interphalangeal joint flexion and index finger distal interphalangeal joint flexion
. Inability to extend the metacarpophalangeal joints of the fingers and thumb
. Decreased sensation over the volar aspect of the little finger
. Inability to abduct and adduct the fingers
. Weakness of elbow flexion and forearm supination

Correct Answer & Explanation

. Inability to extend the metacarpophalangeal joints of the fingers and thumb

Explanation

In a supracondylar humerus fracture with posteromedial displacement of the distal fragment, the proximal fragment displaces anterolaterally. This places the radial nerve at risk of tenting or laceration as it passes through the lateral intermuscular septum. Radial nerve palsy presents with wrist drop and inability to extend the fingers and thumb at the MCP joints. Conversely, posterolateral displacement puts the anterior interosseous nerve (AIN) at risk.

Question 2752

Topic: Pediatric Hip

A 13-year-old boy presents to the emergency department with severe left hip pain after tripping over a curb. He is completely unable to bear weight on the left leg, even with the assistance of crutches. Radiographs demonstrate a severe slipped capital femoral epiphysis (SCFE). Which of the following factors is the most significant predictor for the development of avascular necrosis in this patient?

. The radiographic chronicity of the slip
. The magnitude of epiphyseal displacement
. The inability to bear weight on the affected extremity
. The patient's body mass index (BMI)
. The method chosen for surgical fixation

Correct Answer & Explanation

. The radiographic chronicity of the slip

Explanation

According to the Loder classification, SCFE is categorized as stable or unstable based entirely on the clinical ability of the patient to bear weight (with or without crutches). Unstable SCFE (inability to bear weight) carries a high risk of avascular necrosis (ranging up to nearly 50%), compared to a minimal risk (<5%) in stable SCFE.

Question 2753

Topic: Pediatric Hip

A 13-year-old boy weighing 95 kg presents with left groin pain and an obligatory external rotation of the hip with flexion. Radiographs confirm a left slipped capital femoral epiphysis (SCFE). Which of the following factors is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Age greater than 12 years
. Male sex
. Presentation with an acute slip
. Underlying endocrinopathy
. Obesity (>95th percentile)

Correct Answer & Explanation

. Age greater than 12 years

Explanation

The risk of a contralateral slip in patients with SCFE is approximately 25% to 60%. Absolute or strong relative indications for prophylactic pinning of the contralateral asymptomatic hip include underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), radiation therapy to the pelvis, open triradiate cartilage (young age, e.g., females <10 and males <12), and patients for whom reliable follow-up is unlikely. Age >12, male sex, and obesity alone are not universal indications for prophylactic pinning.

Question 2754

Topic: 4. Pediatrics

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a routine follow-up, the parents report that the child has stopped kicking the affected leg. On examination, there is decreased active extension of the knee, but the child moves the foot and toes spontaneously. What is the most likely cause, and what is the appropriate initial management?

. Sciatic nerve palsy; loosen the posterior straps
. Femoral nerve palsy; temporarily discontinue the harness or loosen the anterior straps
. Obturator nerve palsy; increase hip abduction
. Avascular necrosis of the femoral head; immediate closed reduction and spica casting
. Septic arthritis; immediate aspiration and intravenous antibiotics

Correct Answer & Explanation

. Sciatic nerve palsy; loosen the posterior straps

Explanation

Femoral nerve palsy is the most common nerve palsy associated with the Pavlik harness and is caused by excessive hyperflexion of the hip. Clinically, it presents as a loss of active knee extension. The appropriate management is to temporarily discontinue the harness or loosen the anterior straps to reduce the degree of hip flexion, allowing the nerve to recover. Sciatic nerve palsy is rare and would typically present with distal deficits. AVN and septic arthritis would present with pain and systemic signs, not isolated knee extension weakness.

Question 2755

Topic: Pediatric Hip
A 9-year-old boy presents with a painless limp and restricted hip internal rotation. Radiographs demonstrate fragmentation of the capital femoral epiphysis consistent with Legg-Calvรฉ-Perthes disease. Which of the following factors carries the worst prognosis for this patient?
. Male sex
. Age at presentation
. Presence of a limp
. Decreased internal rotation
. Unilateral involvement

Correct Answer & Explanation

. Age at presentation

Explanation

Age at the onset of symptoms is the most significant prognostic factor in Legg-Calvรฉ-Perthes disease. Children who develop the disease after age 8 have a worse prognosis because they have less time for the femoral head to remodel before skeletal maturity, often leading to a residual aspherical femoral head and early osteoarthritis. The extent of lateral pillar involvement (Herring classification) is also a critical radiographic prognostic factor. Male sex is a risk factor for developing the disease, but older age carries the worst outcome.

Question 2756

Topic: Pediatric Lower Extremity

When treating a rigid idiopathic clubfoot using the Ponseti method of serial casting, what is the correct order of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method follows a strict sequence of correcting the deformities associated with clubfoot, remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The cavus is corrected first by supinating the forefoot and elevating the first ray to align it with the hindfoot. Following this, the foot is abducted to correct the adductus and varus simultaneously, pivoting around the head of the talus. Finally, the equinus is corrected, often requiring a percutaneous Achilles tenotomy.

Question 2757

Topic: Pediatric Hip

A 4-month-old infant presents with a persistently dislocated left hip after a failed 6-week trial of Pavlik harness treatment. Ultrasound confirms the femoral head is dislocated but reducible with moderate force. The acetabulum appears dysplastic. What is the most appropriate next step in management?

. Observation and repeat ultrasound at 6 months of age
. Switch to an abduction orthosis
. Closed reduction and spica casting
. Open reduction and spica casting
. Femoral varus derotational osteotomy

Correct Answer & Explanation

. Observation and repeat ultrasound at 6 months of age

Explanation

After a failed trial of a Pavlik harness in an infant under 6 months of age with developmental dysplasia of the hip (DDH), the next appropriate step is an examination under anesthesia, arthrogram, and closed reduction with spica casting. If closed reduction cannot be achieved or maintained within a safe zone, an open reduction is indicated. Continued observation or switching to another brace has a high failure rate once the Pavlik harness has definitively failed.

Question 2758

Topic: Pediatric Hip

A 12-year-old obese boy presents with acute on chronic left knee pain and an antalgic gait. Physical examination reveals obligate external rotation of the thigh during passive hip flexion. He is diagnosed with a stable slipped capital femoral epiphysis (SCFE) and undergoes in situ pinning with a single cannulated screw. Which of the following is the most significant risk factor for the development of chondrolysis in this patient?

. Patient weight greater than the 95th percentile
. Acute symptom onset
. Unrecognized intra-articular pin penetration
. Delay in surgical intervention
. Use of a single rather than double screw construct

Correct Answer & Explanation

. Patient weight greater than the 95th percentile

Explanation

Chondrolysis is a devastating complication of SCFE characterized by rapid cartilage destruction and joint stiffness. The most significant recognized risk factor for chondrolysis is unrecognized intra-articular pin penetration during surgical fixation. Meticulous fluoroscopic evaluation (including the approach-withdraw technique) is essential to ensure the screw has not breached the articular surface.

Question 2759

Topic: Pediatric Hip

An 8-year-old boy presents with a painless limp. Radiographs demonstrate fragmentation of the capital femoral epiphysis. The treating orthopedic surgeon notes multiple 'head-at-risk' signs on the radiograph. According to Catterall, which of the following is considered a 'head-at-risk' sign in Legg-Calve-Perthes disease?

. Medial epiphyseal cyst
. Gage sign
. Widening of the medial joint space
. Acetabular dysplasia
. Coxa magna

Correct Answer & Explanation

. Medial epiphyseal cyst

Explanation

Catterall described five 'head-at-risk' clinical and radiographic signs indicating a poorer prognosis in Legg-Calve-Perthes disease. The radiographic signs include: Gage sign (a V-shaped radiolucent defect in the lateral portion of the epiphysis and adjacent metaphysis), calcification lateral to the epiphysis, lateral subluxation of the femoral head, a horizontal growth plate, and metaphyseal cysts.

Question 2760

Topic: 4. Pediatrics

A 6-year-old nonambulatory child with spastic quadriplegic cerebral palsy presents for routine evaluation. An anteroposterior pelvis radiograph demonstrates a right hip migration percentage of 55%. The child is currently asymptomatic. What is the most appropriate management?

. Observation and repeat radiographs in 1 year
. Adductor tenotomy alone
. Varus derotational osteotomy (VDRO) of the proximal femur
. Proximal femoral resection (Castle procedure)
. Total hip arthroplasty

Correct Answer & Explanation

. Observation and repeat radiographs in 1 year

Explanation

In a child with cerebral palsy, a hip migration percentage greater than 40-50% indicates significant subluxation and a high risk of progression to dislocation. Soft tissue releases (like adductor tenotomy) alone are insufficient at this stage. Bony reconstruction with a proximal femoral varus derotational osteotomy (VDRO), often combined with a pelvic osteotomy, is the most appropriate treatment to achieve joint congruity and prevent painful dislocation.

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