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Pediatric Hip MCQs

Practice Set 82 of 104

This practice set contains high-yield board review questions covering key concepts in Pediatric Hip. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1621

Topic: Pediatric Hip
In the Herring Lateral Pillar Classification for Legg-Calvé-Perthes disease, a hip demonstrating a lateral pillar that maintains exactly 65% of its original height is classified into which group?
. Group A
. Group B
. Group B/C border
. Group C
. Group D

Correct Answer & Explanation

. Group B

Explanation

The Herring Lateral Pillar Classification relies on the height of the lateral pillar of the femoral head on AP radiograph. Group A has 100% height. Group B maintains >50% of the height. Group C has <50% of the height. Therefore, a lateral pillar at 65% falls squarely into Group B.

Question 1622

Topic: Pediatric Hip

A 6-week-old female is treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 2-week follow-up, she presents with an inability to actively extend her knee on the treated side. Which of the following is the most appropriate next step in management?

. Immediate surgical exploration
. Switch to a rigid hip spica cast
. Loosen the anterior straps of the harness
. Loosen the posterior straps of the harness
. Obtain an urgent MRI of the hip

Correct Answer & Explanation

. Immediate surgical exploration

Explanation

The child has developed a femoral nerve palsy, a known complication of extreme hyperflexion in a Pavlik harness. The anterior straps control hip flexion; therefore, loosening them is the appropriate next step to relieve tension on the femoral nerve. Usually, the nerve function recovers completely once flexion is reduced.

Question 1623

Topic: Pediatric Hip

A 6-week-old female with developmental dysplasia of the hip is treated with a Pavlik harness. After 2 weeks, the mother notes that the infant is no longer actively kicking the affected leg, particularly lacking active knee extension. The most likely cause of this clinical finding is:

. Obturator nerve palsy from excessive abduction
. Sciatic nerve palsy from excessive flexion
. Femoral nerve palsy from hyperflexion
. Tibial nerve palsy from the foot strap
. Avascular necrosis of the femoral head

Correct Answer & Explanation

. Obturator nerve palsy from excessive abduction

Explanation

Femoral nerve palsy is a well-documented complication of the Pavlik harness, typically caused by hyperflexion of the hips compressing the nerve against the inguinal ligament. It presents with decreased active knee extension. Treatment involves adjusting the harness to decrease flexion or temporarily discontinuing it until function returns.

Question 1624

Topic: Pediatric Hip

A 12-year-old boy with a BMI in the 99th percentile presents with a left-sided Slipped Capital Femoral Epiphysis (SCFE) and undergoes in-situ pinning. The parents ask about the risk to his right hip. Which of the following is the most significant risk factor indicating the need for prophylactic pinning of the contralateral, asymptomatic hip?

. Chronological age greater than 14 years
. Hypothyroidism or other endocrinopathy
. Presence of knee pain rather than groin pain
. Left-sided initial presentation
. Male sex

Correct Answer & Explanation

. Chronological age greater than 14 years

Explanation

Prophylactic pinning of the contralateral hip in SCFE is indicated in patients with underlying metabolic or endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or in very young patients (e.g., modified Oxford bone age < 10 for girls or < 12 for boys) because their risk of developing a contralateral slip approaches 50% to 100%.

Question 1625

Topic: Pediatric Hip

A 12-year-old boy with a BMI of 32 presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE) of the left hip. In considering prophylactic pinning of the contralateral, asymptomatic hip, which of the following factors most strongly supports intervention?

. Patient age
. Patient obesity
. Presence of an endocrine disorder
. Male sex
. Severity of the left-sided slip

Correct Answer & Explanation

. Patient age

Explanation

The presence of an endocrine disorder (e.g., hypothyroidism, renal osteodystrophy) significantly increases the risk of a contralateral SCFE, warranting prophylactic pinning. Endocrine etiology is the strongest predictor among these choices.

Question 1626

Topic: Pediatric Hip

A 12-year-old obese male presents with left-sided Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the most accepted indication for prophylactic pinning of the contralateral asymptomatic hip?

. Age greater than 14 years
. Female sex
. Endocrinopathy such as hypothyroidism or renal osteodystrophy
. Mild slip angle (<30 degrees) on the affected side
. Closure of the triradiate cartilage

Correct Answer & Explanation

. Age greater than 14 years

Explanation

Prophylactic pinning of the contralateral hip in SCFE is indicated in patients with endocrinopathies (hypothyroidism, renal osteodystrophy, growth hormone deficiency), previous radiation therapy, and in some centers for very young age (<10 years for boys, <11 for girls) due to the exceedingly high risk of a subsequent contralateral slip.

Question 1627

Topic: Pediatric Hip

A 6-week-old female is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During follow-up, she is noted to have decreased active extension of the knee on the treated side. What is the most likely cause?

. Avascular necrosis of the femoral head
. Femoral nerve palsy due to excessive hip flexion
. Obturator nerve palsy due to excessive abduction
. Development of an iatrogenic knee dislocation
. Sciatic nerve palsy due to excessive hip extension

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by hyperflexion of the hip which compresses the nerve against the inguinal ligament. It presents as decreased active extension of the knee. If this occurs, the harness should be adjusted or temporarily discontinued to prevent permanent nerve injury.

Question 1628

Topic: Pediatric Hip

A 13-year-old boy undergoes in situ pinning with a single cannulated screw for a stable SCFE. Three months postoperatively, he presents with severe hip pain, stiffness, and significantly restricted range of motion in all planes. Radiographs reveal a global joint space of 2 mm. What is the most likely diagnosis?

. Avascular necrosis of the femoral head
. Chondrolysis
. Implant failure
. Femoral neck fracture
. Septic arthritis

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Chondrolysis is a severe complication of SCFE, presenting with acute onset of pain, global restriction of hip motion, and joint space narrowing (<3mm) on radiographs. It is strongly associated with unrecognized intra-articular hardware penetration during pinning.

Question 1629

Topic: Pediatric Hip

A 12-year-old boy with a BMI of 35 presents with acute-on-chronic hip pain. He is diagnosed with a slipped capital femoral epiphysis (SCFE). According to the Loder classification, which clinical finding classifies his SCFE as 'unstable'?

. Slip angle > 50 degrees
. Presence of an intra-articular effusion on ultrasound
. Inability to bear weight on the affected limb, even with crutches
. Duration of symptoms less than 3 weeks
. Displacement of more than 50% of the femoral neck width

Correct Answer & Explanation

. Slip angle > 50 degrees

Explanation

The Loder classification divides SCFE into stable and unstable categories based entirely on the clinical ability to bear weight. An unstable SCFE is defined as the inability to bear weight, even with assistive devices. Unstable SCFEs carry a much higher risk of avascular necrosis (AVN), historically up to 47%.

Question 1630

Topic: Pediatric Hip

An 8-year-old boy is diagnosed with Legg-Calve-Perthes disease. Which of the following radiographic findings is one of Catterall's 'head-at-risk' signs, indicating a poorer prognosis and a higher likelihood of femoral head deformation?

. Medial subluxation of the femoral head
. Gage sign (V-shaped radiolucency in the lateral epiphysis/metaphysis)
. Narrowing of the teardrop distance
. Sclerosis of the central acetabulum
. Premature closure of the greater trochanteric apophysis

Correct Answer & Explanation

. Medial subluxation of the femoral head

Explanation

Catterall described five 'head-at-risk' signs that portend a poor prognosis in Perthes disease: 1) Gage sign (a V-shaped radiolucency in the lateral epiphysis and adjacent metaphysis), 2) Lateral calcification, 3) Lateral subluxation of the femoral head, 4) Metaphyseal cysts, and 5) A horizontal growth plate.

Question 1631

Topic: Pediatric Hip

A 13-year-old boy presents with right hip pain and inability to bear weight for 2 days. X-rays confirm a slipped capital femoral epiphysis. According to the Loder classification, what is the primary prognostic significance of his inability to bear weight?

. High risk of chondrolysis
. High risk of avascular necrosis (AVN)
. Mandates prophylactic contralateral pinning
. Indicates an underlying endocrine disorder
. Predicts a stable, non-progressive course

Correct Answer & Explanation

. High risk of chondrolysis

Explanation

According to the Loder classification, an unstable SCFE is defined by the inability to bear weight even with crutches. Unstable slips carry a significantly higher risk of avascular necrosis (up to nearly 50%) compared to stable slips.

Question 1632

Topic: Pediatric Hip
An 8-year-old boy with Legg-Calvé-Perthes disease is evaluated radiographically. According to the modified lateral pillar (Herring) classification, which finding portends the worst prognosis?
. Greater than 50% maintained lateral pillar height
. Less than 50% maintained lateral pillar height
. Fragmentation of the medial pillar
. Presence of a Gage sign
. Calcification lateral to the epiphysis

Correct Answer & Explanation

. Less than 50% maintained lateral pillar height

Explanation

The Herring (lateral pillar) classification is highly prognostic in Legg-Calvé-Perthes disease. Group C, defined as having less than 50% of the lateral pillar height maintained, predicts a poor radiographic and clinical outcome, particularly in children over 8 years old.

Question 1633

Topic: Pediatric Hip

A 3-year-old girl is diagnosed with untreated developmental dysplasia of the hip (DDH). Radiographs reveal a completely dislocated left hip with a false acetabulum. What is the most appropriate surgical management at this age?

. Closed reduction and spica casting
. Open reduction and spica casting
. Open reduction, femoral shortening osteotomy, and pelvic osteotomy
. Pelvic osteotomy alone
. Observation until skeletal maturity

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

In children over 2 to 3 years of age, soft tissue contractures and acetabular dysplasia require an open reduction combined with a femoral shortening osteotomy (to reduce joint pressure and AVN risk) and a pelvic osteotomy (to improve acetabular coverage).

Question 1634

Topic: Pediatric Hip

A 14-year-old boy undergoes percutaneous in situ pinning for a stable Slipped Capital Femoral Epiphysis (SCFE). Six months later, he presents with severe hip stiffness, pain, and a significant loss of internal rotation and abduction. Radiographs show concentric joint space narrowing of the affected hip. What is the most likely diagnosis?

. Avascular necrosis (AVN)
. Chondrolysis
. Implant failure
. Femoroacetabular impingement (FAI)
. Septic arthritis

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

Concentric joint space narrowing and stiffness following SCFE, especially if a pin penetrated the joint space during surgery, is the hallmark of chondrolysis. Avascular necrosis typically presents with subchondral collapse rather than diffuse joint space loss.

Question 1635

Topic: Pediatric Hip

Which of the following is the primary basis for the Herring Lateral Pillar classification used in Legg-Calve-Perthes disease?

. The degree of subchondral radiolucency (Crescent sign)
. The height of the lateral third of the capital femoral epiphysis on an AP radiograph
. The presence of lateral calcification or ossification in the soft tissues
. The amount of epiphyseal extrusion on a Lauenstein lateral radiograph
. The extent of metaphyseal cyst formation

Correct Answer & Explanation

. The degree of subchondral radiolucency (Crescent sign)

Explanation

The Herring Lateral Pillar classification is based on the height of the lateral pillar of the capital femoral epiphysis on an AP radiograph during the early fragmentation phase. It is the most reliable prognostic indicator for late outcomes.

Question 1636

Topic: Pediatric Hip

In a 7-year-old boy diagnosed with Legg-Calve-Perthes disease, which of the following radiographic findings is considered the most reliable indicator of a poor prognosis according to the Herring classification?

. Gage sign
. Calcification lateral to the epiphysis
. Metaphyseal cysts
. Less than 50% maintenance of the lateral pillar height
. Subchondral fracture line (crescent sign)

Correct Answer & Explanation

. Gage sign

Explanation

The Herring Lateral Pillar classification is the most reliable prognostic indicator for Legg-Calve-Perthes disease. Group C, which involves greater than 50% collapse of the lateral pillar, portends a poor clinical outcome.

Question 1637

Topic: Pediatric Hip

A 3-year-old girl is undergoing surgical treatment for developmental dysplasia of the hip (DDH). The surgeon plans a pelvic osteotomy that involves an incomplete osteotomy of the ilium leaving the sciatic notch intact, hinging on the triradiate cartilage to improve anterolateral coverage. Which osteotomy is being described?

. Salter
. Pemberton
. Dega
. Chiari
. Steel

Correct Answer & Explanation

. Salter

Explanation

The Pemberton osteotomy is an incomplete pericapsular osteotomy that hinges on the flexible triradiate cartilage. It primarily improves anterolateral acetabular coverage without disrupting the sciatic notch and decreases acetabular volume.

Question 1638

Topic: Pediatric Hip

A 13-year-old boy undergoes in situ single-screw fixation for a stable slipped capital femoral epiphysis (SCFE). Which intraoperative technical error is most strongly associated with the development of chondrolysis?

. Pinning the contralateral prophylactic hip
. Penetration of the screw into the joint space
. Placing the screw in the anterior half of the epiphysis
. Using a fully threaded screw instead of a partially threaded screw
. Starting the screw distal to the intertrochanteric line

Correct Answer & Explanation

. Pinning the contralateral prophylactic hip

Explanation

Unrecognized intraoperative joint penetration by the guidewire or screw is the most common iatrogenic cause of chondrolysis in SCFE treatment. An intraoperative "approach-withdraw" fluoroscopic technique is used to prevent this complication.

Question 1639

Topic: Pediatric Hip

In the surgical treatment of a patient with Crowe Type IV developmental dysplasia of the hip (DDH), the surgeon decides to place the acetabular component in the true anatomical paleocenter. What additional surgical step is most frequently required to successfully reduce the hip and minimize the risk of sciatic nerve palsy?

. Greater trochanteric advancement
. Subtrochanteric shortening osteotomy
. Extensive release of the gluteus medius
. Distal femoral lengthening osteotomy
. Placement of a jumbo acetabular component

Correct Answer & Explanation

. Subtrochanteric shortening osteotomy

Explanation

Crowe IV DDH is characterized by a high hip dislocation (>100% subluxation). Pulling the femur down to the true acetabulum stretches the surrounding neurovascular structures, particularly the sciatic nerve. To safely reduce the hip to the anatomical center without causing sciatic nerve palsy, a subtrochanteric shortening osteotomy of the femur is typically required.

Question 1640

Topic: Pediatric Hip

Metal-on-metal (MoM) hip resurfacing arthroplasty (HRA) is occasionally considered for young, active patients. However, strict patient selection is required to prevent early failure. Which of the following patient profiles is universally considered a poor candidate (or absolute contraindication) for HRA due to high failure rates from adverse local tissue reaction and femoral neck fracture?

. A 45-year-old male with severe primary osteoarthritis and a large femoral head
. A 50-year-old male with a history of slipped capital femoral epiphysis (SCFE)
. A 38-year-old female with developmental dysplasia of the hip and a femoral head size of 42 mm
. A 55-year-old male with post-traumatic osteoarthritis and normal bone density
. A 40-year-old male with an isolated cam-type femoroacetabular impingement and cartilage loss

Correct Answer & Explanation

. A 38-year-old female with developmental dysplasia of the hip and a femoral head size of 42 mm

Explanation

Female gender, small femoral head component size (<48 mm), and underlying diagnoses of DDH or AVN (with large cystic changes) are major risk factors for failure in HRA. Small component sizes in MoM bearings lead to reduced fluid-film lubrication, higher wear rates, and increased metal ion release. Additionally, females have a higher rate of femoral neck fractures post-HRA.

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