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Pediatric Hip MCQs

Practice Set 39 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 761

Topic: Pediatric Hip

A 14-year-old male presents with global hip stiffness and pain 8 months after undergoing in-situ single-screw fixation for a stable right SCFE. Radiographs show a joint space of 2 mm and profound osteopenia. The screw tip is positioned 3 mm from the subchondral bone. What is the most likely cause of his current symptoms?

. Avascular necrosis
. Implant failure
. Chondrolysis
. Septic arthritis
. Heterotopic ossification

Correct Answer & Explanation

. Chondrolysis

Explanation

The patient has chondrolysis, characterized by diffuse joint space narrowing (<3 mm) and global loss of motion. The most common cause in the setting of SCFE treatment is unrecognized hardware penetration into the joint space.

Question 762

Topic: Pediatric Hip

During a surgical dislocation and subcapital realignment (modified Dunn procedure) for a severe SCFE, which of the following blood supply sources is most critical to protect while developing the retinacular flap?

. Ascending branch of the lateral femoral circumflex artery
. Deep branch of the medial femoral circumflex artery
. Ligamentum teres artery
. Inferior gluteal artery
. Obturator artery

Correct Answer & Explanation

. Deep branch of the medial femoral circumflex artery

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) provides the primary blood supply to the femoral head. It must be meticulously protected within the retinacular flap during surgical hip dislocation to prevent AVN.

Question 763

Topic: Pediatric Hip

A 12-year-old boy presents with a 3-week history of right hip pain and a limp. He is diagnosed with a stable slipped capital femoral epiphysis (SCFE). Medical history is significant for primary hypothyroidism. Regarding surgical intervention, which of the following is the most appropriate management strategy?

. In situ pinning of the right hip only
. In situ pinning of the right hip and prophylactic pinning of the left hip
. Spica cast application for 6 weeks
. Open reduction and internal fixation of the right hip
. Bilateral proximal femoral osteotomies

Correct Answer & Explanation

. In situ pinning of the right hip and prophylactic pinning of the left hip

Explanation

Patients with endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) have a significantly higher risk of bilateral SCFE. Prophylactic pinning of the contralateral asymptomatic hip is strongly indicated in these populations.

Question 764

Topic: Pediatric Hip

A 24-month-old girl presents with a painless waddling gait. Radiographs reveal a unilaterally dislocated right hip with a false acetabulum and significant dysplasia of the true acetabulum. She has no prior treatment history for this condition. What is the most appropriate definitive management?

. Application of a Pavlik harness
. Closed reduction and spica casting
. Open reduction, capsulorrhaphy, and pelvic/femoral osteotomies
. Observation until skeletal maturity followed by total hip arthroplasty
. Botulinum toxin injections to the adductors and bracing

Correct Answer & Explanation

. Open reduction, capsulorrhaphy, and pelvic/femoral osteotomies

Explanation

In children older than 18 to 24 months presenting with neglected DDH, closed reduction is usually impossible or highly unstable. Open reduction combined with pelvic and/or femoral osteotomies is required to correct the bony dysplasia and maintain reduction.

Question 765

Topic: Pediatric Hip

A 13-year-old boy presents to the emergency department unable to bear weight on his left leg after a minor fall. Radiographs demonstrate a severe slipped capital femoral epiphysis (SCFE). He is scheduled for urgent in situ percutaneous pinning. Based on the stability of his slip, what is the most significant anticipated complication?

. Chondrolysis
. Avascular necrosis (AVN)
. Femoral nerve palsy
. Developmental dysplasia of the hip
. Infection

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

An unstable SCFE is defined clinically by the inability to bear weight, even with crutches. Unstable slips carry a high risk of avascular necrosis (AVN), which can occur in up to 50% of cases regardless of the treatment method.

Question 766

Topic: Pediatric Hip

A 6-week-old infant undergoes a screening ultrasound for developmental dysplasia of the hip (DDH) due to a breech presentation. The report mentions the alpha and beta angles according to the Graf classification. What anatomical structure does the alpha angle primarily evaluate?

. The cartilaginous acetabular roof
. The bony acetabular roof
. The femoral head sphericity
. The degree of labral inversion
. The triradiate cartilage width

Correct Answer & Explanation

. The bony acetabular roof

Explanation

In the Graf ultrasound classification for DDH, the alpha angle measures the concavity and depth of the bony acetabular roof. The beta angle measures the cartilaginous roof.

Question 767

Topic: Pediatric Hip

A 13-year-old boy whose body mass index (BMI) is in the 95th percentile presents with a 4-month history of vague left knee pain. Examination of the knee shows no effusion, and there is full, painless range of motion. Examination of the left hip reveals obligatory external rotation when the hip is flexed to 90 degrees. What is the most appropriate next step in diagnosis?

. MRI of the left knee
. AP and frog-leg lateral radiographs of the pelvis
. Diagnostic ultrasound of the left knee
. Reassurance and nonsteroidal anti-inflammatory drugs
. Technetium-99m bone scan

Correct Answer & Explanation

. AP and frog-leg lateral radiographs of the pelvis

Explanation

This classic presentation (knee pain, obesity, obligatory external rotation with hip flexion) is highly suspicious for a Slipped Capital Femoral Epiphysis (SCFE). Pain is often referred to the knee via the obturator nerve, making AP and frog-leg lateral pelvis radiographs mandatory.

Question 768

Topic: Pediatric Hip

A 14-year-old girl who underwent in situ pinning for a stable left SCFE 6 months ago presents with increasing left hip stiffness and pain. Radiographs demonstrate a diffuse 50% loss of the joint space in the left hip compared to the right, with no signs of hardware failure. What is the most likely diagnosis?

. Avascular necrosis (AVN)
. Chondrolysis
. Septic arthritis
. Implant failure
. Heterotopic ossification

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is characterized by diffuse joint space narrowing, severe stiffness, and pain after SCFE treatment. It is highly associated with unrecognized pin penetration into the hip joint during surgical fixation.

Question 769

Topic: Pediatric Hip

While performing a closed reduction and spica casting for a 9-month-old with developmental dysplasia of the hip (DDH), the surgeon evaluates the 'safe zone' of Ramsey. The hip dislocates in adduction. To minimize the risk of iatrogenic avascular necrosis (AVN) of the femoral head, what position must the surgeon strictly avoid when applying the cast?

. Extreme hip flexion (greater than 100 degrees)
. Extreme hip internal rotation
. Extreme hip abduction (frog-leg position)
. Extreme hip adduction
. Knee flexion of 90 degrees

Correct Answer & Explanation

. Extreme hip abduction (frog-leg position)

Explanation

The safe zone of Ramsey lies between the angle of adduction where the hip dislocates and the angle of maximum abduction. Casting in extreme or forced abduction (the 'frog-leg' position) compromises the retinacular vessels, dramatically increasing the risk of avascular necrosis (AVN).

Question 770

Topic: Pediatric Hip

A 7-month-old girl presents for her first pediatric orthopedic evaluation and is diagnosed with bilateral DDH. Ultrasound confirms bilateral dislocated hips that are irreducible on dynamic examination. What is the most appropriate initial treatment?

. Pavlik harness application
. Closed reduction and spica casting
. Open reduction with bilateral capsulorrhaphy
. Bilateral Salter innominate osteotomies
. Bilateral femoral shortening osteotomies

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

The Pavlik harness has a high failure rate in children older than 6 months and in those with irreducible dislocations. Closed reduction with spica casting under anesthesia is the most appropriate initial intervention for late-presenting DDH at this age.

Question 771

Topic: Pediatric Hip

A 5-year-old girl with residual DDH undergoes preoperative planning for a pelvic osteotomy. The chosen technique is an incomplete pericapsular osteotomy that hinges on the triradiate cartilage, dynamically reducing the volume of the acetabulum. Which osteotomy is described?

. Salter
. Pemberton
. Steel
. Chiari
. Dega

Correct Answer & Explanation

. Pemberton

Explanation

The Pemberton osteotomy is an incomplete pericapsular procedure that hinges at the triradiate cartilage. By changing the shape of the acetabular roof, it inherently reduces the acetabular volume, making it highly effective for true dysplastic, capacious acetabula.

Question 772

Topic: Pediatric Hip

A 4-month-old girl is being treated in a Pavlik harness for developmental dysplasia of the hip (DDH). Her parents report that she is no longer actively extending her right knee. What is the most likely cause of this complication?

. Obturator nerve palsy from excessive abduction
. Femoral nerve palsy from excessive hip flexion
. Sciatic nerve palsy from excessive hip extension
. Superior gluteal nerve palsy from harness straps
. Avascular necrosis of the femoral head

Correct Answer & Explanation

. Femoral nerve palsy from excessive hip flexion

Explanation

Femoral nerve palsy in a Pavlik harness is caused by excessive hip flexion, leading to nerve impingement against the inguinal ligament. It usually resolves completely after temporarily releasing the anterior flexion straps.

Question 773

Topic: Pediatric Hip

An 18-month-old girl presents with untreated developmental dysplasia of the hip (DDH). She has a positive Galeazzi sign and limited hip abduction. What is the most appropriate initial intervention?

. Pavlik harness
. Closed reduction and spica casting
. Open reduction and spica casting
. Femoral shortening osteotomy
. Observation until age 3

Correct Answer & Explanation

. Open reduction and spica casting

Explanation

For DDH presenting at 18 months or older, open reduction is generally the initial treatment of choice. Closed reduction at this age has a high failure rate and an increased risk of AVN.

Question 774

Topic: Pediatric Hip

A 6-week-old female is treated with a Pavlik harness for developmental dysplasia of the hip (DDH). After 1 week, the mother notes the child is no longer kicking her right leg, and the knee rests in extension. What is the most likely cause?

. Obturator nerve palsy
. Femoral nerve palsy
. Sciatic nerve palsy
. Avascular necrosis of the femoral head
. Transient synovitis

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion of the hips in a Pavlik harness can compress the femoral nerve, leading to a transient femoral nerve palsy, indicated by a lack of active knee extension. The harness should be temporarily removed or adjusted (flexion reduced) to resolve the palsy.

Question 775

Topic: Pediatric Hip

A 12-year-old girl with a history of DDH treated with closed reduction at infancy presents with a limp. Radiographs show a shortened, widened femoral neck and an enlarged, flat femoral head. This deformity is most likely a sequela of which complication?

. Septic arthritis
. Unrecognized slipped capital femoral epiphysis
. Missed acetabular dysplasia
. Iatrogenic avascular necrosis
. Legg-Calve-Perthes disease

Correct Answer & Explanation

. Iatrogenic avascular necrosis

Explanation

The classic radiographic findings of coxa magna, coxa brevis, and a flat femoral head in a patient with a history of DDH treatment are indicative of iatrogenic avascular necrosis. This is typically sustained during early immobilization, often due to excessive hip abduction.

Question 776

Topic: Pediatric Hip

A 6-month-old female presents with an asymmetric thigh crease. An AP pelvis radiograph is obtained. Which of the following acetabular index measurements is considered normal for this age?

. 10 degrees
. 22 degrees
. 35 degrees
. 42 degrees
. 50 degrees

Correct Answer & Explanation

. 22 degrees

Explanation

The normal acetabular index in a 6-month-old is generally less than 25 degrees. Values greater than 28-30 degrees are highly suspicious for developmental dysplasia of the hip requiring intervention.

Question 777

Topic: Pediatric Hip

A 4-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up exam, she exhibits absent active knee extension on the treated side. What is the most likely cause of this finding?

. Obturator nerve palsy
. Sciatic nerve palsy
. Femoral nerve palsy
. Avascular necrosis of the femoral head
. Patellar dislocation

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion of the hips in a Pavlik harness can lead to femoral nerve palsy, presenting as decreased active knee extension. The harness must be adjusted or temporarily discontinued until full nerve function recovers.

Question 778

Topic: Pediatric Hip

An 18-month-old girl presents with a painless limp and delayed walking. Examination reveals asymmetric thigh folds and a positive Galeazzi sign. Radiographs confirm a unilateral dislocated hip. What is the most appropriate initial treatment?

. Pavlik harness application
. Rigid abduction orthosis
. Closed reduction and spica casting
. Open reduction and pelvic osteotomy
. Observation until age 3

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

For DDH presenting between 6 and 18 months of age, closed reduction and spica casting under general anesthesia is the standard first-line treatment. A Pavlik harness is ineffective at this age due to infant size and mobility.

Question 779

Topic: Pediatric Hip

On an AP pelvis radiograph of a 6-month-old evaluated for DDH, the proximal femoral metaphysis is located in the upper outer quadrant formed by Hilgenreiner's and Perkin's lines. What does this radiographic finding indicate?

. Normal hip development
. Slipped capital femoral epiphysis
. Acetabular retroversion
. Hip dislocation
. Coxa vara

Correct Answer & Explanation

. Hip dislocation

Explanation

Perkin's line (vertical) and Hilgenreiner's line (horizontal) divide the hip into quadrants. In a normal hip, the medial beak of the metaphysis is in the lower inner quadrant; presence in the upper outer quadrant signifies a dislocated hip.

Question 780

Topic: Pediatric Hip

What is the most critical technical risk factor for the development of iatrogenic avascular necrosis (AVN) of the femoral head during closed reduction and spica casting for DDH?

. Hip extension during the initial reduction maneuver
. Immobilization of the hip in extreme abduction (>60 degrees)
. Inadequate duration of cast immobilization (less than 6 weeks)
. Bilateral hip involvement necessitating a bilateral spica cast
. Use of fiberglass cast material instead of plaster

Correct Answer & Explanation

. Immobilization of the hip in extreme abduction (>60 degrees)

Explanation

Immobilizing the hip in excessive abduction (greater than 60 degrees, the "frog-leg" position) places severe tension on the medial circumflex femoral artery. This is the most significant preventable risk factor for iatrogenic AVN in DDH treatment.

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