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4. Pediatrics MCQs

Practice Set 252 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 5021

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents note that the infant is no longer actively extending her left knee, though she moves her ankle and toes normally. Which of the following is the most likely cause of this finding?

. Sciatic nerve palsy from excessive hip abduction
. Femoral nerve palsy from excessive hip flexion
. Obturator nerve palsy from excessive hip external rotation
. Superior gluteal nerve palsy from harness strap pressure
. Tibial nerve palsy from foot strap tightness

Correct Answer & Explanation

. Sciatic nerve palsy from excessive hip abduction

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment and is typically caused by excessive hip hyperflexion compressing the nerve against the inguinal ligament. It manifests as decreased active quadriceps function (lack of active knee extension) and resolves with adjustment of the flexion straps.

Question 5022

Topic: Pediatric Lower Extremity

An infant is born with bilateral idiopathic clubfeet (talipes equinovarus). The orthopedic surgeon elects to begin treatment using the Ponseti method of serial casting. What is the correct sequence of deformity correction in this method?

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

Correct Answer & Explanation

. Adduction, Cavus, Varus, Equinus

Explanation

The Ponseti method requires sequential correction of the clubfoot deformities using the CAVE mnemonic: Cavus, Adductus, Varus, and finally Equinus. The first step involves elevating the first ray to correct the forefoot cavus, which aligns the forefoot with the midfoot.

Question 5023

Topic: 4. Pediatrics

A 14-year-old elite baseball pitcher presents with dominant shoulder pain during throwing. Radiographs demonstrate widening of the proximal humeral physis. What is the most appropriate initial management?

. Arthroscopic labral repair
. Corticosteroid injection into the subacromial space
. Absolute rest from throwing for 3 months followed by a structured return-to-throw program
. Open epiphysiodesis
. Biceps tenodesis

Correct Answer & Explanation

. Arthroscopic labral repair

Explanation

Little Leaguer's shoulder is a stress fracture (epiphysiolysis) of the proximal humeral physis caused by repetitive rotational torque. The standard of care is complete rest from throwing for approximately 3 months until symptoms resolve, followed by a gradual return.

Question 5024

Topic: Pediatric Hip

A 4-month-old female infant is undergoing radiographic evaluation for suspected developmental dysplasia of the hip (DDH). An AP pelvis radiograph is obtained. Which of the following specific radiographic parameters definitively indicates abnormal acetabular development at this age?

. An acetabular index of 22 degrees
. The ossific nucleus of the femoral head located in the lower inner quadrant of Perkin and Hilgenreiner lines
. A continuous and intact Shenton's line
. An acetabular index of 35 degrees
. A center-edge angle of Wiberg of 30 degrees

Correct Answer & Explanation

. An acetabular index of 22 degrees

Explanation

The acetabular index (AI) measures the slope of the cartilaginous acetabular roof. At birth, a normal AI is less than 30 degrees, and by 6 months, it should typically be less than 25 degrees. An AI of 35 degrees at 4 months is abnormally steep and highly indicative of acetabular dysplasia. The other options describe normal findings: the femoral head normally sits in the lower inner quadrant, Shenton's line should be intact, and an AI of 22 is normal for this age.

Question 5025

Topic: Pediatric Hip

A 13-year-old obese male presents to the emergency department after a minor trip and fall. Radiographs demonstrate a displaced right slipped capital femoral epiphysis (SCFE). On examination, he is completely unable to bear weight on the right leg, even with the assistance of crutches. Which of the following factors is most strongly associated with the high risk of developing osteonecrosis of the femoral head in this specific patient?

. The patient's elevated body mass index (BMI)
. The chronicity of prodromal symptoms prior to the acute slip
. The inability to bear weight on the affected extremity
. The degree of posterior slip angle on the lateral radiograph
. The exact direction of the epiphyseal displacement

Correct Answer & Explanation

. The patient's elevated body mass index (BMI)

Explanation

The inability to bear weight on the affected extremity, even with crutches, defines an 'unstable' SCFE according to the Loder classification. Unstable SCFE is a true orthopedic emergency and carries a high risk of developing avascular necrosis (AVN), reported to be between 20% and 50%. Stable slips (able to bear weight) have an AVN risk approaching 0%.

Question 5026

Topic: 4. Pediatrics
A 7-year-old boy is newly diagnosed with Legg-Calvé-Perthes disease. Which of the following radiographic classifications, applied during the fragmentation stage of the disease, is considered the most reliable indicator of long-term prognosis and risk of irreversible femoral head deformation?
. The Salter-Harris classification
. The Herring Lateral Pillar classification
. The Catterall classification
. The Stulberg classification
. The Waldenström classification

Correct Answer & Explanation

. The Herring Lateral Pillar classification

Explanation

The Herring Lateral Pillar classification, assessed on AP radiographs during the fragmentation phase of Legg-Calvé-Perthes disease, is the most widely accepted and prognostic classification. It divides the femoral head into lateral, central, and medial pillars. The height of the lateral pillar (Group A: >100%, Group B: >50%, Group C: <50%) directly correlates with the ability of the femoral head to bear weight without collapsing, thus predicting long-term sphericity.

Question 5027

Topic: Pediatric Hip

In the pathophysiology of a Slipped Capital Femoral Epiphysis (SCFE), the proximal femoral epiphysis typically remains seated within the acetabulum while the femoral neck displaces. What is the characteristic anatomic direction of the displacement of the femoral metaphysis relative to the epiphysis?

. Posterior and inferior
. Anterior and superior
. Anterior and inferior
. Posterior and superior
. Directly medial

Correct Answer & Explanation

. Posterior and inferior

Explanation

In SCFE, the name is somewhat of a misnomer. The epiphysis does not truly 'slip' out of the acetabulum; rather, it remains seated posteriorly and inferiorly due to the tethering of the ligamentum teres. It is the femoral metaphysis (neck) that displaces anteriorly and superiorly relative to the epiphysis, driven by the mechanical forces of weight-bearing and external rotation acting on a weakened physis.

Question 5028

Topic: Pediatric Hip
A 45-year-old female with developmental dysplasia of the hip (DDH) is planning to undergo a THA. Preoperative radiographs show that her femoral head is subluxated superiorly by 85% of the normal vertical height of the corresponding normal femoral head. Based on the Crowe classification, what type of DDH does she have?
. Crowe I
. Crowe II
. Crowe III
. Crowe IV
. Crowe V

Correct Answer & Explanation

. Crowe III

Explanation

The Crowe classification assesses the degree of proximal subluxation of the femoral head in DDH. Crowe I is <50% subluxation; Crowe II is 50-74% subluxation; Crowe III is 75-99% subluxation; and Crowe IV is 100% or greater subluxation (complete dislocation). An 85% subluxation falls into the Crowe III category.

Question 5029

Topic: Pediatric Hip
A 40-year-old female with bilateral developmental dysplasia of the hip (DDH) presents for THA. Radiographs reveal that the femoral head is subluxated proximally by 80% of the height of the normal acetabulum. According to the Crowe classification, what is her grade?
. Crowe I
. Crowe II
. Crowe III
. Crowe IV
. Crowe V

Correct Answer & Explanation

. Crowe III

Explanation

The Crowe classification for adult DDH measures the amount of proximal subluxation relative to the height of the normal acetabulum. Crowe I: <50%; Crowe II: 50-74%; Crowe III: 75-100%; Crowe IV: >100% (complete dislocation). An 80% subluxation falls into Crowe III.

Question 5030

Topic: Pediatric Hip

A 22-year-old professional hockey player presents with chronic groin pain exacerbated by flexion and internal rotation. AP pelvis radiographs demonstrate a prominent alpha angle of 65 degrees and a positive crossover sign. Which of the following combinations correctly identifies the morphologic deformities present?

. Cam impingement and acetabular retroversion
. Pincer impingement and acetabular anteversion
. Cam impingement and acetabular anteversion
. Pincer impingement and coxa valga
. Cam impingement and coxa vara

Correct Answer & Explanation

. Cam impingement and acetabular retroversion

Explanation

An alpha angle > 55 degrees indicates a lack of femoral head-neck offset, defining a Cam-type femoroacetabular impingement. A positive crossover sign (where the anterior rim of the acetabulum crosses lateral to the posterior rim on an AP pelvis radiograph) is indicative of acetabular retroversion, which causes focal anterior Pincer impingement.

Question 5031

Topic: Pediatric Hip

In the evaluation of Legg-Calve-Perthes Disease (LCPD), Catterall described several 'head at risk' signs that portend a poorer prognosis. Which of the following is one of these classic radiographic signs?

. Gage sign
. Klein's line intersection
. Southwick angle > 30 degrees
. Trethowan sign
. Drehmann sign

Correct Answer & Explanation

. Gage sign

Explanation

Catterall's 'head at risk' signs for Legg-Calve-Perthes Disease include the Gage sign (a V-shaped radiolucent defect in the lateral aspect of the epiphysis/physis), calcification lateral to the epiphysis, lateral subluxation of the femoral head, a horizontal growth plate, and metaphyseal cysts. Klein's line and Trethowan sign are associated with SCFE.

Question 5032

Topic: Pediatric Hip

A 12-year-old obese male presents with left groin pain and a total inability to bear weight on the left leg. Radiographs confirm a severe slipped capital femoral epiphysis (SCFE). He undergoes urgent single-screw in situ fixation. Postoperatively, he develops avascular necrosis (AVN) of the femoral head. Which of the following initial presentation factors is the most significant independent predictor for the development of AVN in this patient?

. Severity of the slip angle (greater than 50 degrees)
. Age of the patient at the time of presentation
. Inability to bear weight prior to surgery (unstable slip)
. Patient obesity (BMI >95th percentile)
. Use of a single screw rather than two screws for fixation

Correct Answer & Explanation

. Severity of the slip angle (greater than 50 degrees)

Explanation

According to Loder's classification, a SCFE is categorized as 'unstable' if the patient is entirely unable to bear weight, even with crutches. Unstable slips have an extremely high rate of avascular necrosis (up to 47-50%), regardless of the treatment method, due to the acute disruption of the retinacular vessels supplying the femoral head. Stable slips have a much lower rate of AVN (<10%). While slip severity increases the risk of osteoarthritis, instability is the paramount risk factor for AVN.

Question 5033

Topic: Pediatric Hip
A 42-year-old female with untreated developmental dysplasia of the hip (DDH) presents for a primary total hip arthroplasty. Preoperative radiographs show a completely dislocated femoral head articulating with a false acetabulum. The proximal migration of the femoral head is measured to be 35% of the vertical height of the normal hemipelvis. According to the Crowe classification, what is her specific grade, and what adjunctive surgical procedure is most routinely required during her THA?
. Crowe II; Femoral head structural autograft for the acetabular roof
. Crowe III; Greater trochanteric advancement
. Crowe IV; Subtrochanteric shortening osteotomy
. Crowe IV; Periacetabular osteotomy
. Crowe III; Distal femoral extension osteotomy

Correct Answer & Explanation

. Crowe IV; Subtrochanteric shortening osteotomy

Explanation

The Crowe classification for DDH evaluates the degree of proximal migration of the femoral head relative to the true acetabulum. A migration of greater than 20% of the pelvic height (or >100% of the femoral head height) defines a Crowe IV dysplasia. Bringing the hip down from this high dislocated position into the true acetabulum places massive tension on the sciatic nerve. To prevent catastrophic sciatic nerve palsy and allow reduction, a subtrochanteric shortening osteotomy of the femur is frequently required.

Question 5034

Topic: Pediatric Hip
A 45-year-old female with adult developmental dysplasia of the hip (DDH) is planned for a primary THA. Preoperative radiographs demonstrate that her femoral head is proximally migrated, equating to 85% subluxation relative to the true acetabulum. According to the Crowe classification, what is her stage, and what surgical complexity is most likely anticipated to achieve reduction into the true acetabulum?
. Crowe I; use of an extra-large 'jumbo' cup without femoral shortening.
. Crowe II; routine primary stem insertion.
. Crowe III; high likelihood of requiring a subtrochanteric shortening osteotomy or accepting a high hip center.
. Crowe IV; standard reduction easily achievable by complete capsular release.
. Crowe I; varus derotational osteotomy alone.

Correct Answer & Explanation

. Crowe III; high likelihood of requiring a subtrochanteric shortening osteotomy or accepting a high hip center.

Explanation

The Crowe classification stages DDH based on the percentage of proximal subluxation (proximal migration divided by vertical head height). Crowe I: <50%, Crowe II: 50-74%, Crowe III: 75-100%, Crowe IV: >100% (complete dislocation). At 85% subluxation, she is Crowe III. Bringing the femoral head down to the true acetabulum in Crowe III and IV hips often stretches the sciatic nerve beyond its physical tolerance (typically a limit of 3-4 cm of lengthening). Therefore, a subtrochanteric shortening osteotomy is frequently required to reduce the joint safely without catastrophic nerve palsy.

Question 5035

Topic: Pediatric Hip

An overweight 13-year-old boy presents with right thigh pain and an obligatory external rotation of the hip during active hip flexion. Radiographs confirm a mild stable slipped capital femoral epiphysis (SCFE). During in situ single-screw fixation, where should the screw ideally be placed within the epiphysis?

. Anterior-superior quadrant
. Anterior-inferior quadrant
. Posterior-superior quadrant
. Posterior-inferior quadrant
. Directly central in both AP and lateral planes

Correct Answer & Explanation

. Anterior-superior quadrant

Explanation

The ideal starting point for in situ pinning of a SCFE is on the anterior neck, aiming for the center-center position of the epiphysis on both the anteroposterior and lateral radiographic views. This central placement minimizes the risk of joint penetration and avoids the lateral epiphyseal vessels, reducing the risk of avascular necrosis.

Question 5036

Topic: Pediatric Hip

A 6-month-old female is diagnosed with developmental dysplasia of the hip (DDH) after failing Pavlik harness treatment. A closed reduction and spica casting are planned. To minimize the risk of avascular necrosis (AVN) of the femoral head during casting, what is the safest position for the hip?

. 90-100 degrees of flexion and less than 60 degrees of abduction
. 120 degrees of flexion and 90 degrees of abduction
. Neutral flexion and maximal internal rotation
. Extension and maximal abduction
. 110 degrees of flexion and maximal external rotation

Correct Answer & Explanation

. 90-100 degrees of flexion and less than 60 degrees of abduction

Explanation

Immobilizing the hip in extreme abduction (the classic 'frog-leg' position) dramatically increases the risk of AVN, particularly of the posterosuperior aspect of the femoral head, due to compression of the medial circumflex femoral artery branches. The 'safe zone' of Ramsey requires casting the hip in 90-100 degrees of flexion and moderate abduction (typically <60 degrees).

Question 5037

Topic: Pediatric Lower Extremity

In the Ponseti method for the treatment of idiopathic clubfoot, the sequence of correction is paramount. Which of the following components of the deformity is corrected first?

. Equinus
. Varus
. Adductus
. Cavus
. Internal rotation

Correct Answer & Explanation

. Equinus

Explanation

The Ponseti method follows a strict sequence of correction summarized by the acronym CAVE: Cavus, Adductus, Varus, Equinus. The first step is to correct the cavus deformity by supinating the forefoot to align it with the hindfoot, effectively elevating the first ray.

Question 5038

Topic: 4. Pediatrics

A 4-year-old girl is evaluated for short stature, frontal bossing, and rhizomelic shortening of the limbs. Radiographs show narrowing of the interpedicular distances in the lumbar spine. A mutation in which of the following genes is the definitive cause?

. COL1A1
. FGFR3
. COMP
. RUNX2
. SOX9

Correct Answer & Explanation

. COL1A1

Explanation

The clinical and radiographic presentation is classic for achondroplasia. It is caused by an activating mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene, leading to inhibition of chondrocyte proliferation in the proliferative zone of the physis.

Question 5039

Topic: Pediatric Hip

A 6-year-old boy presents with a painless limp. Radiographs reveal sclerosis and fragmentation of the proximal femoral epiphysis. According to the Herring lateral pillar classification, which of the following describes a Group B hip?

. No involvement of the lateral pillar
. >50% maintenance of lateral pillar height
. <50% maintenance of lateral pillar height
. Complete collapse of the lateral pillar
. Involvement of only the medial pillar

Correct Answer & Explanation

. No involvement of the lateral pillar

Explanation

The Herring lateral pillar classification for Legg-Calve-Perthes disease evaluates the height of the lateral portion of the capital femoral epiphysis on an AP radiograph. Group A has 100% height maintained, Group B maintains >50% height, and Group C has <50% height maintained.

Question 5040

Topic: 4. Pediatrics

A 13-year-old obese boy presents with left knee pain and a limp for 3 weeks. Examination reveals limited internal rotation of the left hip. When the hip is flexed, it obligatorily externally rotates. Radiographs show a widening of the left proximal femoral physis. What is the most appropriate definitive treatment?

. Spica casting
. Closed reduction and internal fixation
. In situ single screw fixation
. Proximal femoral osteotomy
. Physical therapy and weight loss

Correct Answer & Explanation

. Spica casting

Explanation

Slipped Capital Femoral Epiphysis (SCFE) frequently presents with thigh or knee pain and obligate external rotation upon hip flexion. The gold standard treatment is in situ stabilization with a single cannulated screw to prevent further slip without increasing the risk of avascular necrosis via reduction maneuvers.

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