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4. Pediatrics MCQs

Practice Set 83 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 1641

Topic: Pediatric Hip
Figures 20a and 20b show the radiographs of an obese 15-year-old boy who has severe left groin pain and is unable to bear weight following a minor injury. Treatment should consist of
. fixation with one or two screws.
. cast immobilization.
. manipulative reduction with single screw fixation.
. in situ fixation with multiple screws.
. open epiphyseodesis.

Correct Answer & Explanation

. fixation with one or two screws.

Explanation

DISCUSSION: The radiographs and history are consistent with an acute unstable slipped capital femoral epiphysis. Aronson and Loder documented an increased rate of osteonecrosis associated with manipulative reduction. They recommended bed rest with skin traction to allow the synovitis to resolve, followed by in situ pinning. They noted, however, that many of these slips reduced with anesthesia and positioning on a fracture table. Biomechanic studies have shown a slight increased resistance to shear stress when two screws are used, but it is unknown if this is significant in the clinical setting. Open epiphyseodesis does not provide postoperative stability; therefore, adjunctive fixation or immobilization is required. Numerous studies have noted the inadvisability of using multiple screws. Casting has a high rate of complications, including chondrolysis and progression of the slip.

Question 1642

Topic: 4. Pediatrics
During stabilization of a slipped capital femoral epiphysis, the screw penetrates into the joint. The screw is repositioned so that it is within the femoral head. This transient penetration of the hip joint will most likely lead to
. an increased risk of chondrolysis.
. an increased risk of osteonecrosis.
. an increased risk of stiffness.
. an increased time to closure of the physis.
. no deleterious effect.

Correct Answer & Explanation

. no deleterious effect.

Explanation

DISCUSSION: Chondrolysis may be associated with unrecognized permanent penetration of the joint space by a pin or screw. However, transient penetration by the guide wire or screw is not associated with this problem. One study described 11 hips in which there was transient intraoperative penetration of the joint space by a guide wire or screw. These patients were followed for at least 2 years, with none showing any clinical or radiographic evidence of chondrolysis. Another retrospective study of 55 slipped epiphyses described 11 hips with transient intraoperative pin penetration, with none showing development of chondrolysis. There are no studies to suggest that transient pin penetration leads to osteonecrosis, stiffness, or premature physeal closure.

Question 1643

Topic: 4. Pediatrics

In a 4-year-old child with developmental dysplasia of the hip, an osteotomy is planned to improve anterolateral acetabular coverage. The osteotomy is described as an incomplete pericapsular cut that hinges on the triradiate cartilage without extending into the sciatic notch. Which osteotomy is being described?

. Salter
. Pemberton
. Chiari
. Dega
. Triple

Correct Answer & Explanation

. Salter

Explanation

The Pemberton osteotomy is an incomplete pericapsular osteotomy that cuts through the ilium down to, and hinging on, the flexible triradiate cartilage. This allows the acetabular roof to be hinged downward to improve anterolateral coverage. A Salter osteotomy is a complete transiliac cut that hinges on the pubic symphysis.

Question 1644

Topic: 4. Pediatrics
A 2.5-year-old obese girl presents with bilateral genu varum. Radiographs show a metaphyseal-diaphyseal angle (Drennan's angle) of 18 degrees and medial physeal beaking. What is the most appropriate initial management?
. Observation with reassurance
. Knee-ankle-foot orthoses (KAFOs)
. Proximal tibial valgus osteotomy
. Guided growth (hemiepiphysiodesis)
. Vitamin D supplementation

Correct Answer & Explanation

. Knee-ankle-foot orthoses (KAFOs)

Explanation

The patient has infantile Blount's disease (Langenskiöld stage I/II), indicated by her age, obesity, metaphyseal-diaphyseal angle > 16 degrees, and physeal beaking. In a child under 3 years old, conservative management with daytime bracing (KAFO) is the standard initial treatment. Surgery is reserved for older children or failure of bracing.

Question 1645

Topic: Pediatric Hip

A 13-year-old boy presents with severe left hip pain and inability to bear weight following a minor fall. Radiographs confirm a severe, unstable slipped capital femoral epiphysis (SCFE). A modified Dunn procedure is considered. What vascular structure is most at risk and must be meticulously protected during the surgical dislocation and callus debridement?

. Medial femoral circumflex artery (MFCA)
. Lateral femoral circumflex artery (LFCA)
. Artery of the ligamentum teres
. Inferior gluteal artery
. Deep external pudendal artery

Correct Answer & Explanation

. Medial femoral circumflex artery (MFCA)

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) is the primary blood supply to the femoral head. In the modified Dunn procedure (capital realignment via surgical hip dislocation) for severe unstable SCFE, the retinacular vessels branching from the MFCA must be meticulously preserved as they run along the posterosuperior femoral neck to prevent avascular necrosis (AVN).

Question 1646

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Which of the following radiographic findings is recognized as one of Catterall's 'head-at-risk' signs, indicating a poorer prognosis?
. Central calcification of the capital epiphysis
. Gage's sign
. Acetabular retroversion
. Medial subluxation of the femoral head
. Preservation of the lateral pillar

Correct Answer & Explanation

. Gage's sign

Explanation

Catterall's 'head-at-risk' signs for poor prognosis in Perthes disease include: Gage's sign (a V-shaped radiolucency in the lateral portion of the epiphysis/metaphysis), lateral subluxation of the femoral head, calcification lateral to the epiphysis, diffuse metaphyseal reaction, and a horizontal growth plate.

Question 1647

Topic: 4. Pediatrics

A 4-month-old infant with developmental dysplasia of the hip is being treated with a Pavlik harness. During a follow-up visit, the infant is noted to lack active knee extension on the treated side, though there is normal ankle movement. What is the most appropriate next step in management?

. Decrease the flexion of the anterior straps
. Increase the abduction of the posterior straps
. Remove the harness completely and observe for recovery
. Switch immediately to a rigid abduction orthosis
. Perform a closed reduction and spica cast application

Correct Answer & Explanation

. Decrease the flexion of the anterior straps

Explanation

A lack of active knee extension in an infant treated with a Pavlik harness indicates a femoral nerve palsy, a known complication caused by hyperflexion. The initial and most appropriate treatment is to completely remove the harness to allow the nerve to recover. Continuing the harness, even with adjustments, risks further permanent nerve damage or complete failure of the harness treatment (Pavlik disease).

Question 1648

Topic: 4. Pediatrics

A newborn is diagnosed with Congenital Femoral Deficiency (CFD). During the comprehensive orthopedic evaluation, the surgeon must actively screen for commonly associated anomalies. Which of the following conditions is LEAST likely to be associated with CFD?

. Fibular hemimelia
. Anterior cruciate ligament (ACL) deficiency
. Coxa vara
. Patellar instability
. Tibial hemimelia

Correct Answer & Explanation

. Tibial hemimelia

Explanation

Congenital Femoral Deficiency (CFD), formerly known as PFFD, belongs to the 'lateral ray' developmental field defect. It is highly associated with fibular hemimelia, ACL deficiency, coxa vara, and patellar instability. Tibial hemimelia is a 'medial ray' deficiency and is generally not associated with CFD.

Question 1649

Topic: 4. Pediatrics

A 4-year-old boy with Proximal Focal Femoral Deficiency (PFFD) is evaluated for a Van Nes rotationplasty. For this procedure to be functionally successful, which of the following anatomic prerequisites is absolutely essential?

. A fully formed femoral head and intact hip joint
. An intact anterior cruciate ligament
. A functional, stable ankle joint with active plantarflexion and dorsiflexion
. A projected leg length discrepancy of less than 10 cm
. An intact proximal fibular physis

Correct Answer & Explanation

. A functional, stable ankle joint with active plantarflexion and dorsiflexion

Explanation

In a Van Nes rotationplasty, the limb is rotated 180 degrees so that the ankle joint functions as the new knee joint for the prosthetic fitting. Therefore, a fully functional, mobile, and stable ankle joint with active motor control is a strict prerequisite for the procedure's functional success.

Question 1650

Topic: Pediatric Hip

In the management of Legg-Calve-Perthes disease, the Herring Lateral Pillar Classification is widely used due to its strong prognostic value. Which radiographic feature specifically defines a Herring Group B classification?

. No involvement of the lateral pillar
. Greater than 50% of the lateral pillar height is maintained
. Less than 50% of the lateral pillar height is maintained
. Collapse of the entire femoral head with extrusion > 20%
. Complete fragmentation of the central pillar sparing the lateral pillar

Correct Answer & Explanation

. Less than 50% of the lateral pillar height is maintained

Explanation

The Herring Lateral Pillar classification evaluates the height of the lateral third of the femoral head on an AP pelvis radiograph during the fragmentation stage. Group A: No involvement of the lateral pillar. Group B: >50% of lateral pillar height is maintained. Group C: <50% of lateral pillar height is maintained. Group B/C border refers to exactly 50% height.

Question 1651

Topic: 4. Pediatrics

A 2-year-old obese child presents with bilateral genu varum. You are distinguishing between physiologic bowing and infantile Blount disease. On standing AP radiographs, measurement of the metaphyseal-diaphyseal angle (MDA) of Drennan is performed. An angle greater than what threshold is highly predictive of progression to infantile Blount disease?

. 5 degrees
. 9 degrees
. 11 degrees
. 16 degrees
. 20 degrees

Correct Answer & Explanation

. 16 degrees

Explanation

Drennan's metaphyseal-diaphyseal angle (MDA) is used to differentiate physiologic bowing from infantile Blount disease. An angle > 16 degrees represents a high probability of progression to Blount disease. An angle < 10 degrees is typical of physiologic bowing, while 10-16 degrees is an indeterminate 'gray zone' requiring close observation.

Question 1652

Topic: 4. Pediatrics

When using a hexapod external fixator (e.g., Taylor Spatial Frame) for complex lower extremity deformity correction, what represents its primary biomechanical and functional advantage over a traditional Ilizarov circular frame?

. It uses half-pins exclusively, eliminating the need for tensioned transfixion wires.
. It corrects all six degrees of freedom simultaneously through a virtual hinge without requiring mechanical frame modification.
. It allows for immediate full weight-bearing on post-operative day one regardless of the osteotomy site.
. It relies strictly on the principle of dynamic axial dynamization to stimulate bone healing.
. It requires placement of the osteotomy strictly at the exact center of rotation of angulation (CORA) for any multiplanar correction.

Correct Answer & Explanation

. It corrects all six degrees of freedom simultaneously through a virtual hinge without requiring mechanical frame modification.

Explanation

The primary advantage of hexapod systems (utilizing the Stewart-Gough platform concept) is the ability to correct complex deformities in all six degrees of freedom simultaneously. It uses a computer-generated 'virtual hinge', allowing continuous multiplanar correction by simply adjusting strut lengths daily, whereas a traditional Ilizarov frame requires physical dismantling and remounting of hinges/constructs to correct multiple planes or sequential translation/angulation.

Question 1653

Topic: 4. Pediatrics

A 6-week-old infant is treated with a Pavlik harness for developmental dysplasia of the hip. At the first follow-up, the parents report the infant is no longer kicking the affected leg. Examination reveals decreased active knee extension but normal foot movements. What is the most appropriate next step?

. Immediate open reduction of the hip
. Adjust the anterior strap to decrease hip flexion
. Adjust the posterior strap to decrease hip abduction
. Abandon the harness and switch to a spica cast
. Order an immediate MRI of the lumbar spine

Correct Answer & Explanation

. Adjust the anterior strap to decrease hip flexion

Explanation

Decreased active knee extension indicates a femoral nerve palsy, a known complication of hyperflexion in a Pavlik harness. The anterior strap must be loosened to decrease hip flexion and relieve tension on the femoral nerve.

Question 1654

Topic: Pediatric Lower Extremity

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

. Equinus, Varus, Adduction, Cavus
. Cavus, Adduction, Varus, Equinus
. Adduction, Varus, Cavus, Equinus
. Cavus, Varus, Adduction, Equinus
. Equinus, Cavus, Adduction, Varus

Correct Answer & Explanation

. Cavus, Adduction, Varus, Equinus

Explanation

The Ponseti method follows the CAVE mnemonic: Cavus (corrected by elevating the first ray), Adduction, Varus, and finally Equinus. Correcting the equinus last typically requires a percutaneous Achilles tenotomy.

Question 1655

Topic: 4. Pediatrics

A 6-year-old boy is diagnosed with Legg-Calve-Perthes disease. Which of the following radiographic findings represents one of Catterall's 'head-at-risk' signs, indicating a poorer prognosis?

. Medial epiphyseal extrusion
. Sclerosis of the acetabular roof
. Decreased medial joint space
. Gage sign
. Premature closure of the greater trochanteric physis

Correct Answer & Explanation

. Gage sign

Explanation

Catterall's 'head-at-risk' signs include Gage sign (a V-shaped radiolucency in the lateral epiphysis/metaphysis), lateral calcification, lateral subluxation, a horizontal physis, and metaphyseal cysts.

Question 1656

Topic: Pediatric Hip

A 12-year-old obese male undergoes in-situ pinning for a slipped capital femoral epiphysis (SCFE). Intraoperatively, the slip is noted to be unstable as the patient could not bear weight prior to surgery. Compared to a stable SCFE, this patient is at significantly higher risk for which complication?

. Chondrolysis
. Avascular necrosis of the femoral head
. Subtrochanteric femur fracture
. Progressive slip
. Femoroacetabular impingement

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Unstable SCFE, defined by the inability to bear weight even with crutches, carries a markedly higher risk of avascular necrosis (AVN) compared to stable SCFE. This is due to disruption or kinking of the retinacular vessels.

Question 1657

Topic: Pediatric Hip

A 30-year-old male presents with activity-related groin pain. Pelvic radiographs reveal a crossover sign, a prominent ischial spine sign, and a posterior wall sign. Which anatomic abnormality is primarily responsible for his femoroacetabular impingement?

. Decreased femoral head-neck offset
. Acetabular retroversion
. Coxa profunda
. Slipped capital femoral epiphysis deformity
. Protrusio acetabuli

Correct Answer & Explanation

. Acetabular retroversion

Explanation

The crossover sign, ischial spine sign, and posterior wall sign are classic radiographic hallmarks of acetabular retroversion, which leads to focal anterior pincer-type impingement.

Question 1658

Topic: 4. Pediatrics

In an 8-year-old boy undergoing guided growth for genu valgum with a tension band plate (8-plate) on the medial distal femur, how does this implant alter the physis compared to traditional rigid Blount staples?

. It rigidly compresses the central physis to halt all longitudinal growth
. It allows for physeal divergence as the screw heads angle with growth
. It causes permanent physeal arrest via an extraperiosteal tether
. It relies on absolute rigid fixation to prevent screw back-out

Correct Answer & Explanation

. It rigidly compresses the central physis to halt all longitudinal growth

Explanation

The tension band plate functions as a flexible hinge. The screws are not locked to the plate, allowing them to diverge as the bone grows, which reduces the risk of hardware failure and permanent physeal arrest seen with rigid staples.

Question 1659

Topic: Pediatric Hip

A 13-year-old obese boy requires in-situ pinning for a stable slipped capital femoral epiphysis (SCFE). To minimize the risk of joint penetration while maximizing mechanical stability, the single screw should be placed in which zone of the femoral head?

. Anterior-superior
. Anterior-inferior
. Posterior-superior
. Central-central

Correct Answer & Explanation

. Anterior-superior

Explanation

In SCFE pinning, the goal is to place a single screw in the center of the epiphysis (central-central position) perpendicular to the physis. This provides optimal stability and minimizes the risk of unrecognized intra-articular screw penetration.

Question 1660

Topic: Pediatric Hip

A 6-year-old boy is diagnosed with Legg-Calve-Perthes disease. Radiographs reveal that exactly 60% of the lateral pillar height is maintained. According to the Herring lateral pillar classification, what is his group and the most appropriate standard initial management?

. Group A - Proximal femoral osteotomy
. Group B - Symptomatic observation and range of motion
. Group C - Pelvic osteotomy
. Group B/C - Immediate hip spica casting

Correct Answer & Explanation

. Group A - Proximal femoral osteotomy

Explanation

Maintenance of >50% lateral pillar height defines Herring Group B. In a patient under the age of 8, Group B disease is typically treated non-operatively with observation, activity modification, and maintaining range of motion.

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