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Pediatric Hip MCQs

Practice Set 77 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 1521

Topic: Pediatric Hip
A 6-year-old boy presents with a painless limp and restricted hip abduction and internal rotation. Radiographs reveal fragmentation of the capital femoral epiphysis with a prominent subchondral lucency (crescent sign). According to the lateral pillar (Herring) classification, what specific radiographic criterion defines a Group B classification?
. No radiolucency in the lateral pillar and normal height
. >50% of the lateral pillar height is maintained compared to the contralateral side
. <50% of the lateral pillar height is maintained compared to the contralateral side
. Extrusion of the epiphysis >20% beyond the lateral margin of the acetabulum
. Central pillar depression with entirely intact medial and lateral pillars

Correct Answer & Explanation

. >50% of the lateral pillar height is maintained compared to the contralateral side

Explanation

Legg-Calvé-Perthes disease is characterized by idiopathic avascular necrosis of the proximal femoral epiphysis in children. The Herring (Lateral Pillar) classification is assessed during the fragmentation phase on AP radiographs and is highly prognostic. Group A: No involvement of the lateral pillar (100% height maintained). Group B: >50% of lateral pillar height is maintained. Group C: <50% of lateral pillar height is maintained. Group B/C border: Exactly 50% height maintained. Patients >8 years old at onset with Group B, and all patients with Group C, generally have a poorer prognosis and are more likely to require surgical containment.

Question 1522

Topic: Pediatric Hip

Which of the following represents an absolute indication for prophylactic in situ pinning of the contralateral hip in a pediatric patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. Age greater than 14 years at presentation
. Concomitant renal osteodystrophy or endocrine disorder
. Female gender
. African American race
. Obesity greater than the 95th percentile for age

Correct Answer & Explanation

. Age greater than 14 years at presentation

Explanation

Prophylactic pinning of the contralateral hip in SCFE is generally indicated in patients with a high risk of subsequent bilateral involvement. Absolute indications typically include endocrine or systemic metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) and prior pelvic radiation. Relative indications include very young presentation (age < 10 years).

Question 1523

Topic: Pediatric Hip

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a routine follow-up, the mother notes the child is no longer actively extending her knee on the treated side. What is the most likely iatrogenic cause of this physical finding?

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

Correct Answer & Explanation

. Obturator nerve palsy due to excessive abduction

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment and is caused by excessive hip flexion, which compresses the femoral nerve against the inguinal ligament or the rim of the pelvis. It presents as diminished quadriceps activity and decreased knee extension. Treatment involves loosening the anterior straps or removing the harness temporarily.

Question 1524

Topic: Pediatric Hip

A 6-month-old female with developmental dysplasia of the hip (DDH) has been managed in a Pavlik harness for 4 weeks. Serial ultrasound imaging today demonstrates persistent dislocation of the left hip. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 4 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld splint)
. Abandon the harness and proceed to closed reduction and spica casting
. Perform an immediate open reduction
. Adjust the Pavlik harness to increase hip flexion past 120 degrees

Correct Answer & Explanation

. Continue the Pavlik harness for an additional 4 weeks

Explanation

Failure of a Pavlik harness to achieve reduction after 3 to 4 weeks warrants its removal to prevent 'Pavlik harness disease' (posterior acetabular wear and worsening dysplasia). The next appropriate step is closed reduction and application of a hip spica cast.

Question 1525

Topic: Pediatric Hip

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The mother notes that the child has stopped actively extending the knee on the affected side. Hyperflexion of the hip in the harness is suspected. Which nerve is most likely compressed?

. Sciatic nerve
. Femoral nerve
. Obturator nerve
. Superior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament. This results in a transient femoral nerve palsy, presenting clinically as a loss of active knee extension.

Question 1526

Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. According to the Herring lateral pillar classification, which radiographic feature defines a Group C hip?
. >50% preserved height of the lateral pillar
. >50% loss of height of the lateral pillar
. 100% involvement of the medial pillar
. Subchondral fracture line (crescent sign)
. Extrusion of the femoral head >20%

Correct Answer & Explanation

. >50% loss of height of the lateral pillar

Explanation

In the Herring lateral pillar classification, Group C is defined by greater than 50% loss of height of the lateral pillar of the femoral head. This classification carries a poor prognosis for spherical head remodeling.

Question 1527

Topic: Pediatric Hip

When evaluating an anteroposterior pelvic radiograph of a 4-month-old infant for Developmental Dysplasia of the Hip (DDH), Hilgenreiner's line is drawn as a horizontal line through which of the following landmarks?

. The lateral margin of the acetabular roof
. The superolateral edge of the ossified femoral head
. The triradiate cartilages of the acetabulum
. The inferior margin of the superior pubic ramus
. The greater sciatic notch

Correct Answer & Explanation

. The lateral margin of the acetabular roof

Explanation

Hilgenreiner's line is a horizontal reference line drawn through the right and left triradiate cartilages on an AP pelvis radiograph. Perkin's line is drawn perpendicularly to Hilgenreiner's line at the lateral edge of the acetabulum. The femoral head should normally reside in the inferomedial quadrant formed by these lines.

Question 1528

Topic: Pediatric Hip

An 8-year-old boy presents with an acute on chronic slipped capital femoral epiphysis (SCFE). Because of the patient's atypical age at presentation, an underlying endocrine disorder must be strongly suspected. Which of the following is the most common endocrine etiology associated with atypical SCFE?

. Hyperthyroidism
. Hypothyroidism
. Cushing's disease
. Addison's disease
. Precocious puberty

Correct Answer & Explanation

. Hyperthyroidism

Explanation

Atypical SCFE includes presentations in children younger than 10 or older than 16, children whose weight is less than the 50th percentile, or bilateral sequential slips. Hypothyroidism is the most common endocrine disorder associated with SCFE. Other associated conditions include growth hormone deficiency and renal osteodystrophy.

Question 1529

Topic: Pediatric Hip
A 21-year-old hockey player presents with chronic groin pain exacerbated by deep flexion. Examination reveals a positive anterior impingement (FADIR) test. AP pelvis and Dunn lateral radiographs are obtained. The radiograph shows an alpha angle of 68 degrees. This finding is most characteristic of which pathomorphology?
. Pincer impingement due to acetabular retroversion
. Cam impingement due to asphericity of the anterolateral femoral head-neck junction
. Dysplastic hip with insufficient lateral center edge angle
. Slipped capital femoral epiphysis
. Legg-Calvé-Perthes disease

Correct Answer & Explanation

. Cam impingement due to asphericity of the anterolateral femoral head-neck junction

Explanation

An alpha angle greater than 50-55 degrees on a lateral or Dunn view of the hip indicates Cam morphology, characterized by asphericity (a "bump") at the anterolateral femoral head-neck junction. This bony prominence impacts the anterosuperior acetabular rim during flexion and internal rotation, causing labral and chondral damage.

Question 1530

Topic: Pediatric Hip

A newborn has a swollen, externally rotated, and shortened right lower extremity following a breech delivery. Radiographs show the right femoral shaft displaced superiorly and laterally, but the femoral head ossification center is absent. Ultrasound confirms the femoral head remains within the acetabulum. What is the most likely diagnosis?

. Developmental dysplasia of the hip (DDH)
. Septic arthritis of the hip
. Proximal femoral focal deficiency
. Transepiphyseal separation of the proximal femur
. Midshaft femur fracture

Correct Answer & Explanation

. Developmental dysplasia of the hip (DDH)

Explanation

Transepiphyseal separation of the proximal femur in neonates often mimics hip dislocation on plain film because the proximal epiphysis is unossified. Ultrasound or an arthrogram is crucial to distinguish it from DDH by confirming the head is located in the acetabulum.

Question 1531

Topic: Pediatric Hip

A 12-year-old obese boy presents with a 3-week history of left knee pain and an antalgic gait. Examination reveals obligatory external rotation of the left hip upon flexion. Which of the following is considered an absolute indication for prophylactic in situ pinning of the asymptomatic contralateral hip in a patient with a Slipped Capital Femoral Epiphysis (SCFE)?

. Age greater than 14 years at initial presentation
. Initial presentation of a stable slip
. Presence of an underlying endocrine disorder
. Body Mass Index > 95th percentile
. Southwick slip angle greater than 50 degrees on the affected side

Correct Answer & Explanation

. Age greater than 14 years at initial presentation

Explanation

Prophylactic pinning of the contralateral asymptomatic hip in SCFE is controversial but is universally recommended in patients with a high risk of subsequent contralateral slippage. Absolute indications for prophylactic contralateral pinning include underlying endocrine disorders (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency), prior radiation therapy, or presentation at an abnormally young age (typically under 10 years). While obesity and severe slip angles increase the mechanical risk, they are considered relative indications.

Question 1532

Topic: Pediatric Hip

A 6-month-old infant is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip (DDH). During a scheduled follow-up, the mother notes the child is no longer kicking the right leg. Physical examination confirms an absence of active knee extension on the right side. Which of the following specific positioning errors in the harness most likely caused this complication?

. Excessive hip flexion
. Inadequate hip flexion
. Excessive hip abduction
. Inadequate hip abduction
. Excessive hip external rotation

Correct Answer & Explanation

. Excessive hip flexion

Explanation

The patient is presenting with a femoral nerve palsy, a known complication of the Pavlik harness. It is classically caused by hyperflexion of the hip (excessive hip flexion), which compresses the femoral nerve against the inguinal ligament. Treatment involves temporary cessation of harness use or adjusting the anterior straps to decrease flexion until function returns. In contrast, excessive hip abduction in the harness significantly increases the risk of avascular necrosis (AVN) of the femoral head.

Question 1533

Topic: Pediatric Hip

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the two-week follow-up, the parents report the baby has stopped kicking the affected leg. On examination, the hip remains reduced, but there is an absence of active knee extension. Which of the following complications has most likely occurred?

. Sciatic nerve palsy due to excessive abduction
. Femoral nerve palsy due to excessive hyperflexion
. Obturator nerve palsy due to excessive adduction
. Inferior gluteal nerve palsy due to tightness of the posterior strap
. Peroneal nerve palsy due to compression from the foot stirrup

Correct Answer & Explanation

. Sciatic nerve palsy due to excessive abduction

Explanation

Femoral nerve palsy is the most common nerve injury associated with the Pavlik harness, occurring in roughly 2% of cases. It is typically caused by excessive flexion of the hip (anterior straps too tight), which compresses the femoral nerve against the inguinal ligament or the rim of the pelvis. Clinically, it presents as an inability to actively extend the knee. Management involves altering the harness settings or temporarily discontinuing it to allow nerve recovery.

Question 1534

Topic: Pediatric Hip

A 13-year-old obese male presents with left hip pain, an antalgic gait, and obligate external rotation upon hip flexion. Radiographs confirm a left-sided Slipped Capital Femoral Epiphysis (SCFE). The surgeon discusses in-situ pinning of the left hip and considers prophylactic pinning of the asymptomatic right hip. Which of the following is the most established indication for prophylactic fixation of the contralateral hip in SCFE?

. Male sex
. Chronologic age greater than 14 years
. An underlying endocrine disorder (e.g., hypothyroidism)
. A body mass index (BMI) > 95th percentile
. Presence of a slipped capital femoral epiphysis on the left side (side-specific risk)

Correct Answer & Explanation

. Male sex

Explanation

While prophylactic contralateral pinning in SCFE remains controversial for the idiopathic obese patient, it is strongly indicated and widely accepted in patients with underlying endocrinopathies (such as hypothyroidism, growth hormone deficiency, or panhypopituitarism) and in those with renal osteodystrophy. These systemic conditions place the patient at an exceptionally high risk (up to 100% in some series) for developing a contralateral slip. Younger age (e.g., girls < 10, boys < 12) or open triradiate cartilage are also relative indications, but endocrine disorders are the strongest and most universally accepted absolute indication.

Question 1535

Topic: Pediatric Hip

A 6-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the left hip (DDH). At the 3-week ultrasound follow-up, the hip remains dislocated and cannot be reduced in the harness. What is the most appropriate next step in management?

. Continue Pavlik harness for an additional 3 weeks
. Switch to a rigid abduction orthosis (e.g., Ilfeld brace)
. Perform a closed reduction and application of a spica cast
. Perform an open reduction and application of a spica cast
. Botulinum toxin injection into the adductors

Correct Answer & Explanation

. Continue Pavlik harness for an additional 3 weeks

Explanation

If a Pavlik harness fails to achieve reduction within 3 to 4 weeks, continuing it increases the risk of 'Pavlik harness disease' (excoriation, nerve palsy, and persistent posterior wear of the acetabulum). Transitioning to a rigid abduction brace is the recommended next step before attempting closed reduction under anesthesia.

Question 1536

Topic: Pediatric Hip

A 12-year-old boy undergoes an uncomplicated in situ pinning for an unstable slipped capital femoral epiphysis (SCFE). Six months later, he develops acute, severe hip stiffness and a pronounced antalgic gait. Radiographs reveal a uniform and rapid narrowing of the joint space. What is the most likely diagnosis?

. Avascular necrosis of the femoral head
. Chondrolysis
. Septic arthritis
. Femoroacetabular impingement
. Unrecognized slipped contralateral hip

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Chondrolysis is a severe complication following SCFE, characterized by acute, painful stiffness and rapid, uniform loss of the articular cartilage space on radiographs. It is strongly associated with unrecognized hardware penetration into the joint space during pinning.

Question 1537

Topic: Pediatric Hip

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the follow-up visit, the parents report the infant is no longer kicking the right leg actively. Examination reveals an inability to actively extend the right knee. Which of the following positioning errors is most likely responsible for this complication?

. Excessive hip abduction
. Excessive hip flexion
. Excessive hip extension
. Inadequate hip flexion
. Inadequate hip abduction

Correct Answer & Explanation

. Excessive hip abduction

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive hip flexion. It generally resolves with temporary adjustment or removal of the harness.

Question 1538

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 2-week follow-up, the mother notes the infant is no longer kicking her leg on the treated side. Examination reveals a lack of active knee extension. What is the most appropriate next step in management?

. Immediate closed reduction and spica casting
. Open reduction of the hip
. Adjust the anterior straps to increase hip flexion
. Remove the harness and observe for spontaneous recovery
. Switch immediately to a rigid abduction orthosis (e.g., Rhino cruiser)

Correct Answer & Explanation

. Immediate closed reduction and spica casting

Explanation

A lack of active knee extension in a Pavlik harness indicates a femoral nerve palsy caused by hyperflexion of the hip. The standard of care is to remove the harness to decompress the nerve, which typically results in spontaneous recovery.

Question 1539

Topic: Pediatric Hip



An 8-year-old boy presents with an antalgic gait and is diagnosed with Legg-Calve-Perthes disease. Radiographs are utilized to determine the Herring Lateral Pillar classification. A significantly poorer long-term prognosis is most strongly associated with involvement of what percentage of the lateral pillar height?

. < 25% depression of the lateral pillar
. 25-50% depression of the lateral pillar
. > 50% depression of the lateral pillar
. Complete sparing of the lateral pillar
. Isolated depression of the medial pillar

Correct Answer & Explanation

. < 25% depression of the lateral pillar

Explanation

The Herring Lateral Pillar classification is strongly prognostic in Legg-Calve-Perthes. Group C is defined by >50% loss of lateral pillar height and carries the poorest prognosis, with a high likelihood of asynchronous healing and early degenerative joint disease.

Question 1540

Topic: Pediatric Hip

A 12-year-old obese male presents with a limp and right anterior thigh pain for three weeks. Examination reveals an obligate external rotation of the right hip during passive flexion. What is the most appropriate definitive management for his right hip?

. Physical therapy focusing on abductor strengthening
. Application of a hip spica cast
. In situ percutaneous pinning
. Open reduction and internal fixation with a dynamic hip screw
. Proximal femoral corrective osteotomy

Correct Answer & Explanation

. Physical therapy focusing on abductor strengthening

Explanation

The clinical picture is classic for a Slipped Capital Femoral Epiphysis (SCFE). The gold standard for definitive management of a stable SCFE is in situ percutaneous pinning using a single large cannulated screw to prevent further slip.

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