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4. Pediatrics MCQs

Practice Set 321 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 6401

Topic: Pediatric Hip

An 11-year-old obese male presents with acute severe groin pain and inability to bear weight on his right leg after a minor fall. Radiographs reveal an unstable slipped capital femoral epiphysis (SCFE). Which of the following interventions has the highest risk of causing avascular necrosis (AVN) of the femoral head in this setting?

. In situ pinning with a single screw.
. Forceful closed reduction before pinning.
. Open reduction via a surgical hip dislocation approach.
. Percutaneous pinning utilizing two screws.
. Capsulotomy without reduction.

Correct Answer & Explanation

. Forceful closed reduction before pinning.

Explanation

Forceful or non-gentle closed reduction of an unstable SCFE is highly associated with an increased risk of AVN due to kinking or disruption of the fragile retinacular vessels. Current best practices favor either in situ fixation with incidental reduction or an open reduction (e.g., modified Dunn procedure).

Question 6402

Topic: Pediatric Hip

A 5-month-old female with developmental dysplasia of the hip (DDH) has been treated in a Pavlik harness for 4 weeks. Ultrasound demonstrates continued complete dislocation of the left hip with no signs of reduction. What is the most appropriate next step in management?

. Continue Pavlik harness for 4 more weeks.
. Switch to a rigid abduction orthosis (e.g., Ilfeld splint).
. Proceed directly to open reduction and femoral shortening.
. Discontinue the harness and plan for closed reduction and spica casting.
. Perform a pelvic osteotomy.

Correct Answer & Explanation

. Discontinue the harness and plan for closed reduction and spica casting.

Explanation

If a hip remains completely dislocated after 3 to 4 weeks in a Pavlik harness, it must be discontinued to prevent damage to the posterior acetabulum (Pavlik harness disease). The subsequent step in a child of this age is typically a closed reduction under anesthesia followed by spica casting.

Question 6403

Topic: Pediatric Lower Extremity

A newborn is diagnosed with Proximal Focal Femoral Deficiency (PFFD). Radiographs demonstrate absence of the proximal femur, but an MRI confirms a cartilaginous connection between the present femoral head and the femoral shaft. According to the Aitken classification, this represents which class, and what is the typical long-term functional procedure if a severe leg-length discrepancy is expected?

. Aitken A; rotationplasty or amputation/prosthesis.
. Aitken B; acute limb lengthening.
. Aitken C; hip fusion.
. Aitken D; rotationplasty.
. Aitken A; immediate epiphysiodesis.

Correct Answer & Explanation

. Aitken A; rotationplasty or amputation/prosthesis.

Explanation

Aitken Class A PFFD is characterized by a present femoral head and a cartilaginous connection to the shaft that will eventually ossify. Due to severe leg-length discrepancies, early lengthening is often contraindicated, and definitive functional procedures like a Van Nes rotationplasty or Syme amputation with a prosthesis are commonly performed.

Question 6404

Topic: 4. Pediatrics
Which of the following radiographic findings in Legg-Calvé-Perthes disease is considered one of Catterall's 'head-at-risk' signs, indicating a potentially poorer prognosis?
. Medial subluxation of the femoral head.
. Gage's sign (V-shaped radiolucency in the lateral epiphysis/physis).
. Increased epiphyseal height.
. Narrowing of the teardrop distance.
. Sclerosis of the medial femoral neck.

Correct Answer & Explanation

. Gage's sign (V-shaped radiolucency in the lateral epiphysis/physis).

Explanation

Catterall's 'head-at-risk' signs include Gage's sign (a V-shaped radiolucency in the lateral epiphysis/physis), lateral subluxation of the femoral head, calcification lateral to the epiphysis, a horizontal growth plate, and diffuse metaphyseal reactions. These suggest an increased risk for severe deformity.

Question 6405

Topic: 4. Pediatrics



When applying an Ilizarov circular frame for tibial lengthening, which frame modification most effectively increases the axial stiffness of the construct?

. Decreasing the tension on the crossing wires.
. Increasing the diameter of the rings.
. Decreasing the distance between the ring and the bone.
. Using a single wire per ring instead of two.
. Using smooth wires instead of olive wires.

Correct Answer & Explanation

. Decreasing the distance between the ring and the bone.

Explanation

Frame stability and axial stiffness in circular fixators are increased by using smaller diameter rings, which decreases the bone-to-ring distance. Other methods to increase stiffness include increasing wire tension, using olive wires, and crossing wires at angles closer to 90 degrees.

Question 6406

Topic: Pediatric Lower Extremity

In the Ponseti method for the treatment of idiopathic clubfoot, what is the strictly required sequence of deformity correction during serial casting?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus.

Explanation

The Ponseti method follows the CAVE mnemonic for the order of correction: Cavus (corrected first by supinating the forefoot and elevating the first ray), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy).

Question 6407

Topic: 4. Pediatrics

A 12-year-old boy presents with a proximal tibial deformity. Radiographic analysis reveals the center of rotation of angulation (CORA) is located at the level of the physis. To prevent growth arrest, the surgeon plans to perform a diaphyseal osteotomy distal to the CORA. To fully correct the mechanical axis without creating a secondary translation deformity, where should the hinge axis be placed?

. At the level of the osteotomy site
. At the CORA
. Distal to the osteotomy site
. Proximal to the CORA
. At the mechanical axis of the knee

Correct Answer & Explanation

. At the CORA

Explanation

According to Paley's rules of deformity correction, if the osteotomy is performed at a level different from the CORA, the hinge axis must be placed at the CORA to fully align the mechanical axis. This results in angulation and translation at the osteotomy site.

Question 6408

Topic: Pediatric Hip

A 14-year-old obese male presents with acute onset of severe hip pain and inability to bear weight. Radiographs confirm an unstable slipped capital femoral epiphysis (SCFE). He undergoes urgent in situ single-screw fixation. Which of the following complications is most highly associated with this specific presentation?

. Chondrolysis
. Avascular necrosis (AVN)
. Leg length discrepancy
. Implant failure
. Femoroacetabular impingement

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

Unstable SCFE (defined by the inability to bear weight) carries a high risk of avascular necrosis (up to 50%), regardless of the treatment method, due to the disruption of the epiphyseal blood supply.

Question 6409

Topic: Pediatric Hip

A 4-year-old girl is diagnosed with developmental dysplasia of the hip (DDH). Radiographs demonstrate an acetabular index of 40 degrees with anterolateral acetabular deficiency. The surgeon decides to perform a Pemberton osteotomy. What is the primary hinge point for this specific pelvic osteotomy?

. Pubic symphysis
. Sacroiliac joint
. Triradiate cartilage
. Ischial spine
. Obturator foramen

Correct Answer & Explanation

. Triradiate cartilage

Explanation

The Pemberton osteotomy is an incomplete pericapsular osteotomy that hinges on the flexible triradiate cartilage, allowing the acetabular roof to be hinged downward, reducing acetabular volume and improving anterolateral coverage.

Question 6410

Topic: 4. Pediatrics

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

. It allows weight-bearing immediately after application
. It relies entirely on wire tension for stability rather than half-pins
. It permits simultaneous correction of all six degrees of freedom
. It requires the hinge to be manually placed exactly at the CORA
. It eliminates the need for distraction osteogenesis

Correct Answer & Explanation

. It permits simultaneous correction of all six degrees of freedom

Explanation

The hexapod frame uses computer software and six variable-length struts to allow simultaneous correction of angulation, translation, and rotation (six degrees of freedom) without needing to manually change hinges and construct components like a traditional Ilizarov frame.

Question 6411

Topic: 4. Pediatrics
A 9-year-old girl presents with severe, progressive infantile Blount's disease. Radiographs reveal a Langenskiöld stage VI lesion with a complete medial physeal bar and severe depression of the medial tibial plateau. Which of the following surgical strategies is most appropriate?
. Lateral hemiepiphysiodesis alone
. Proximal tibial valgus producing osteotomy without joint elevation
. Medial plateau elevation osteotomy combined with metaphyseal corrective osteotomy
. Observation and bracing
. Medial epiphysiolysis with fat interposition

Correct Answer & Explanation

. Medial plateau elevation osteotomy combined with metaphyseal corrective osteotomy

Explanation

In Langenskiöld stage V and VI (advanced Blount's), there is a medial physeal bar and significant joint incongruity (medial plateau depression). Treatment requires elevation of the medial plateau to restore the joint line, along with a metaphyseal osteotomy to correct the overall mechanical axis.

Question 6412

Topic: Pediatric Lower Extremity

An infant with a severe idiopathic clubfoot is being treated with the Ponseti method of serial casting. The physician is manipulating the foot to correct the sequence of deformities. What is the final deformity to be corrected, often requiring a percutaneous tenotomy?

. Cavus
. Adductus
. Varus
. Equinus
. Supination

Correct Answer & Explanation

. Cavus

Explanation

The sequence of correction in the Ponseti method is CAVE: Cavus, Adductus, Varus, and finally Equinus. Equinus is corrected last, and a percutaneous Achilles tenotomy is required in approximately 80-90% of cases to achieve dorsiflexion.

Question 6413

Topic: 4. Pediatrics

In distraction osteogenesis for limb lengthening, a latency period is strictly observed before starting distraction. Following latency, what is the generally accepted optimal rate and rhythm of distraction to promote high-quality bone regenerate while preventing premature consolidation?

. 0.5 mm per day in 1 increment
. 1.0 mm per day divided into 4 increments
. 2.0 mm per day divided into 2 increments
. 1.5 mm per day in 1 increment
. 0.25 mm per day continuously

Correct Answer & Explanation

. 1.0 mm per day divided into 4 increments

Explanation

The optimal rate of distraction for bone regeneration, originally described by Ilizarov, is 1.0 mm per day. The optimal rhythm is frequent, small increments, typically 0.25 mm four times a day.

Question 6414

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Which of the following radiographic classifications is most reliable for determining the long-term prognosis and likelihood of a spherical femoral head?
. Catterall classification
. Salter-Thompson classification
. Herring lateral pillar classification
. Stulberg classification
. Waldenström staging

Correct Answer & Explanation

. Herring lateral pillar classification

Explanation

The Herring lateral pillar classification evaluates the height of the lateral aspect of the capital femoral epiphysis during the fragmentation stage and is the most reliable prognostic indicator for final head shape in Perthes disease.

Question 6415

Topic: 4. Pediatrics

A 2-year-old child presents with bilateral genu varum. Radiographs reveal a metaphyseal-diaphyseal angle (MDA) of 18 degrees bilaterally. Which of the following is the most appropriate management?

. Observation and reassurance
. Vitamin D supplementation
. Bilateral knee-ankle-foot orthoses (KAFOs)
. Bilateral proximal tibial osteotomies
. Guided growth with tension band plates

Correct Answer & Explanation

. Bilateral knee-ankle-foot orthoses (KAFOs)

Explanation

An MDA greater than 16 degrees in a young child strongly predicts progression to infantile Blount's disease rather than physiologic bowing. The standard initial treatment for a child under 3 years with an MDA > 16 degrees is bracing with KAFOs.

Question 6416

Topic: Pediatric Hip

Which of the following findings is the most reliable determinant of 'instability' in a slipped capital femoral epiphysis (SCFE) according to the Loder classification?

. A slip angle greater than 50 degrees
. Presence of a joint effusion on ultrasound
. Inability to ambulate with or without crutches
. Disruption of the Shenton line
. A physeal step-off greater than 50% of the neck width

Correct Answer & Explanation

. Inability to ambulate with or without crutches

Explanation

The Loder classification defines an unstable SCFE based strictly on the clinical inability of the patient to bear weight, even with assistive devices like crutches. Unstable slips carry a significantly higher risk of avascular necrosis.

Question 6417

Topic: Pediatric Hip
According to the Herring Lateral Pillar Classification for Legg-Calvé-Perthes disease, a patient whose lateral pillar height is maintained at 40% of its normal height falls into which group, and what is the general prognosis?
. Group A; excellent prognosis
. Group B; fair to good prognosis
. Group B/C; fair prognosis
. Group C; poor prognosis
. Group D; universally poor prognosis

Correct Answer & Explanation

. Group C; poor prognosis

Explanation

Herring Group C is defined by a lateral pillar height of less than 50% of the normal height. This group has a generally poor prognosis, carrying a significantly higher risk of aspherical head remodeling and early osteoarthritis.

Question 6418

Topic: Pediatric Lower Extremity

In the Ponseti method for clubfoot casting, which of the following represents the correct sequential order of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method strictly corrects the deformities in the order of CAVE: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot.

Question 6419

Topic: Pediatric Hip

A 45-year-old female with developmental dysplasia of the hip (DDH) Crowe type IV undergoes a total hip arthroplasty. To safely reduce the hip to the true acetabulum and minimize the risk of sciatic nerve palsy, which surgical maneuver is most frequently required?

. Greater trochanteric advancement
. Distal femoral shortening osteotomy
. Subtrochanteric shortening osteotomy
. Pelvic support osteotomy
. Extensive capsular plication

Correct Answer & Explanation

. Subtrochanteric shortening osteotomy

Explanation

In Crowe IV DDH, the femoral head is highly dislocated. Reducing the hip to the anatomic true acetabulum stretches the sciatic nerve; a subtrochanteric shortening osteotomy is commonly required to avoid stretch injury to the nerve.

Question 6420

Topic: Pediatric Hip
Which patient with Legg-Calvé-Perthes disease would show the most significant radiographic benefit from a surgical containment procedure (e.g., proximal femoral or pelvic osteotomy)?
. A 5-year-old with Herring lateral pillar group A
. A 6-year-old with Herring lateral pillar group B
. A 9-year-old with Herring lateral pillar group B/C border
. A 10-year-old with Herring lateral pillar group C
. A 4-year-old with Herring lateral pillar group C

Correct Answer & Explanation

. A 9-year-old with Herring lateral pillar group B/C border

Explanation

Surgical containment provides the greatest benefit in children over 8 years of age at disease onset who have Herring lateral pillar B or B/C border involvement. Patients in group C generally have poor outcomes regardless of the intervention.

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