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Pediatric Hip MCQs

Practice Set 43 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 841

Topic: Pediatric Hip

A 6-week-old infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. Two weeks later, the parents report that the infant is no longer actively kicking the right leg. On examination, the knee lacks active extension. Which of the following is the most likely cause of this complication?

. Excessive abduction in the anterior straps
. Excessive flexion in the anterior straps
. Inadequate flexion in the posterior straps
. Avascular necrosis of the femoral head
. Transient synovitis

Correct Answer & Explanation

. Excessive abduction in the anterior straps

Explanation

Excessive flexion in the anterior straps of a Pavlik harness (typically >120 degrees) can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. The harness should be temporarily discontinued or adjusted.

Question 842

Topic: Pediatric Hip

A 2-year-old girl presents with a limp. Radiographs reveal a previously undiagnosed left-sided developmental dysplasia of the hip (DDH) with complete dislocation. What is the most appropriate definitive management?

. Application of a Pavlik harness
. Closed reduction and spica casting
. Open reduction, capsulorrhaphy, and pelvic osteotomy
. Botulinum toxin injection to the adductors
. Wait until skeletal maturity for a total hip arthroplasty

Correct Answer & Explanation

. Application of a Pavlik harness

Explanation

In a child over 18-24 months of age with a completely dislocated hip, closed reduction is rarely successful or stable. Open reduction combined with a pelvic osteotomy (and sometimes a femoral shortening osteotomy) is indicated to address secondary acetabular dysplasia.

Question 843

Topic: Pediatric Hip

During open reduction for developmental dysplasia of the hip (DDH) through an anterior approach, several anatomic structures can block concentric reduction. Which structure typically causes the 'hourglass' constriction of the joint capsule?

. Transverse acetabular ligament
. Ligamentum teres
. Inverted limbus
. Iliopsoas tendon
. Pulvinar

Correct Answer & Explanation

. Transverse acetabular ligament

Explanation

The iliopsoas tendon crosses the anterior capsule and compresses it, creating an 'hourglass' shape that acts as a primary extra-articular block to reduction. This tendon must be released during an anterior open reduction.

Question 844

Topic: Pediatric Hip

When interpreting an infant hip ultrasound for DDH using the Graf method, the alpha angle is measured. What does the alpha angle specifically quantify?

. The cartilaginous roof coverage
. The bony roof of the acetabulum
. The degree of femoral head lateralization
. The sphericity of the femoral head
. The version of the femoral neck

Correct Answer & Explanation

. The cartilaginous roof coverage

Explanation

The alpha angle in the Graf classification measures the bony roof of the acetabulum. An alpha angle greater than or equal to 60 degrees is considered normal (Type I).

Question 845

Topic: Pediatric Hip

During a Pemberton pericapsular osteotomy for DDH, the osteotomy cut is directed toward and hinges on which of the following structures?

. Sacroiliac joint
. Symphysis pubis
. Ischial spine
. Triradiate cartilage
. Greater sciatic notch

Correct Answer & Explanation

. Sacroiliac joint

Explanation

The Pemberton osteotomy is an incomplete pericapsular pelvic osteotomy that hinges on the flexible triradiate cartilage. It relies on the plasticity of this cartilage to allow the acetabular roof to be rotated downward, thus improving coverage and decreasing acetabular volume.

Question 846

Topic: Pediatric Hip

A 2-month-old infant is diagnosed with developmental dysplasia of the hip (DDH). In which of the following scenarios is the use of a Pavlik harness absolutely contraindicated?

. Bilateral hip dislocation
. Alpha angle of 45 degrees on ultrasound
. Teratologic hip dislocation associated with arthrogryposis
. Positive Ortolani sign on examination
. Failure of previous double-diapering therapy

Correct Answer & Explanation

. Bilateral hip dislocation

Explanation

The Pavlik harness relies on active infant motion to achieve and maintain reduction. It is contraindicated in teratologic dislocations, such as those associated with arthrogryposis or spina bifida, where muscle imbalance and stiffness prevent successful reduction.

Question 847

Topic: Pediatric Hip

A 3-year-old girl presents with a painless limp. Examination reveals a positive Trendelenburg sign on the right. Radiographs confirm an untreated, complete right-sided developmental dislocation of the hip (DDH). What is the most appropriate initial definitive management?

. Pavlik harness application
. Closed reduction and spica cast application
. Open reduction alone
. Open reduction combined with pelvic and femoral shortening osteotomies
. Observation until skeletal maturity followed by total hip arthroplasty

Correct Answer & Explanation

. Pavlik harness application

Explanation

In a child older than 2 to 3 years with an untreated complete DDH, significant acetabular dysplasia and soft tissue contractures are present. Management typically requires an open reduction, a pelvic osteotomy to correct acetabular dysplasia, and a femoral shortening osteotomy to reduce the joint without excessive pressure.

Question 848

Topic: Pediatric Hip

A 12-year-old obese boy presents with acute, severe hip pain and inability to bear weight after a minor twisting injury. Radiographs confirm a severe, unstable slipped capital femoral epiphysis (SCFE). What is the most devastating complication directly associated with the instability of this specific fracture pattern?

. Chondrolysis
. Avascular necrosis of the femoral head
. Early onset osteoarthritis
. Femoroacetabular impingement
. Contralateral slip

Correct Answer & Explanation

. Chondrolysis

Explanation

An unstable SCFE (defined by the inability to bear weight even with crutches) has a significantly higher risk of avascular necrosis (up to 47%) compared to stable slips. The disruption of the precarious retinacular blood supply during the acute slip or forced reduction causes the AVN.

Question 849

Topic: Pediatric Hip

During ultrasound screening for DDH in a 6-week-old infant, the Graf classification is utilized. What specifically does the alpha angle measure on the coronal ultrasound image?

. The degree of cartilaginous roof coverage
. The degree of bony roof coverage
. The depth of the pulvinar
. The inversion of the limbus
. The angle of the femoral neck anteversion

Correct Answer & Explanation

. The degree of cartilaginous roof coverage

Explanation

In the Graf ultrasound method, the alpha angle measures the concavity of the bony acetabular roof relative to the straight iliac bone. An alpha angle greater than 60 degrees is considered normal and indicates adequate bony coverage.

Question 850

Topic: Pediatric Hip

A 4-month-old girl with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the infant exhibits decreased spontaneous movement of the affected side's knee and no active knee extension. What is the most likely cause of this finding?

. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Obturator nerve palsy
. Septic arthritis of the hip
. Sciatic nerve palsy

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Excessive hip flexion in a Pavlik harness can lead to femoral nerve palsy, presenting as decreased active knee extension. The harness must be adjusted or temporarily discontinued to allow neurological recovery.

Question 851

Topic: Pediatric Hip

An 18-month-old girl is diagnosed with residual acetabular dysplasia following successful closed reduction of DDH. Her current acetabular index (AI) is 38 degrees. What is considered the upper limit of normal for the acetabular index at this age?

. 15 degrees
. 20 degrees
. 25 degrees
. 30 degrees
. 35 degrees

Correct Answer & Explanation

. 15 degrees

Explanation

In children older than 1 year, an acetabular index greater than 25 degrees is generally considered abnormal and indicative of dysplasia. Persistent elevation may necessitate a pelvic osteotomy.

Question 852

Topic: Pediatric Hip

A newborn with arthrogryposis multiplex congenita is found to have bilateral rigid, dislocated hips. Which of the following statements regarding the management of these hips is most accurate?

. Pavlik harness treatment is highly successful.
. Closed reduction is typically achievable by 3 months of age.
. Bilateral dislocations are often left untreated due to a high risk of stiffness and recurrence.
. Early open reduction is mandatory to achieve ambulation.
. Femoral shortening is contraindicated in arthrogrypotic hips.

Correct Answer & Explanation

. Pavlik harness treatment is highly successful.

Explanation

Teratologic hip dislocations in arthrogryposis are extremely rigid. Bilateral dislocations are frequently left untreated because surgical intervention carries a high risk of severe stiffness, while unreduced bilateral hips still permit functional ambulation.

Question 853

Topic: Pediatric Hip

Following closed reduction and spica casting for DDH, a 1-year-old child's radiograph demonstrates failure of the ossific nucleus to appear within 1 year post-reduction. The femoral head appears broad and the neck is short. This presentation is most consistent with which complication?

. Residual acetabular dysplasia
. Avascular necrosis (AVN) of the femoral head
. Coxa magna
. Slipped capital femoral epiphysis
. Septic arthritis

Correct Answer & Explanation

. Residual acetabular dysplasia

Explanation

Failure of the ossific nucleus to appear within 1 year, or early signs of a broad head and short neck (coxa brevis), are classic radiographic indicators of avascular necrosis following DDH treatment. It is primarily associated with extreme abduction in the spica cast.

Question 854

Topic: Pediatric Hip

A 6-week-old female infant, born in the breech presentation, is evaluated for developmental dysplasia of the hip (DDH). Ultrasound reveals an alpha angle of 48 degrees and a beta angle of 80 degrees on the left hip. The hip is stable on clinical exam. What is the most appropriate management?

. Observation and repeat ultrasound in 1 month
. Application of a Pavlik harness
. Rigid abduction bracing
. Closed reduction and spica casting
. Open reduction

Correct Answer & Explanation

. Observation and repeat ultrasound in 1 month

Explanation

An alpha angle of less than 60 degrees indicates acetabular dysplasia (Graf type II or worse). In a 6-week-old infant with dysplasia, a Pavlik harness is the gold standard initial treatment to promote normal acetabular development.

Question 855

Topic: Pediatric Hip

A 3-year-old child presents with a neglected right developmental dysplasia of the hip (DDH). She undergoes an open reduction, pelvic osteotomy, and femoral shortening osteotomy. Which of the following is the most devastating complication specific to the surgical treatment of DDH?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Sciatic nerve palsy
. Leg length discrepancy
. Heterotopic ossification

Correct Answer & Explanation

. Chondrolysis

Explanation

Avascular necrosis of the femoral head is the most severe and specific complication of DDH treatment, often resulting from excessive pressure on the femoral head or disruption of the medial circumflex femoral artery during reduction.

Question 856

Topic: Pediatric Hip

A 5-month-old infant with developmental dysplasia of the hip has been treated in a Pavlik harness for 4 weeks. Repeat ultrasound reveals that the left hip remains persistently dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for another 4 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld brace)
. Closed reduction and spica casting under general anesthesia
. Open reduction and pelvic osteotomy
. Femoral varus derotational osteotomy

Correct Answer & Explanation

. Continue the Pavlik harness for another 4 weeks

Explanation

Failure to achieve reduction in a Pavlik harness after 3-4 weeks requires abandonment of the harness to prevent "Pavlik harness disease" (damage to the posterior acetabular wall). The next step is closed reduction and spica casting under anesthesia.

Question 857

Topic: Pediatric Hip

During the radiographic evaluation of a 2-year-old child for developmental dysplasia of the hip (DDH), the orthopedist draws a horizontal line connecting the bilateral triradiate cartilages. What is the name of this reference line?

. Perkin's line
. Hilgenreiner's line
. Shenton's line
. Wiberg's angle
. Klein's line

Correct Answer & Explanation

. Perkin's line

Explanation

Hilgenreiner's line is a horizontal line drawn through the bilateral triradiate cartilages. Perkin's line is drawn perpendicular to Hilgenreiner's line at the lateral edge of the acetabulum, creating quadrants to locate the ossific nucleus of the femoral head.

Question 858

Topic: Pediatric Hip

A 6-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 1-week follow-up, the mother notes that the child has stopped extending the knee on the affected side. On examination, the quadriceps are flaccid. What is the most appropriate next step in management?

. Continue the Pavlik harness and reassure the mother
. Discontinue the Pavlik harness and observe for neurologic recovery
. Adjust the anterior strap to increase hip flexion
. Adjust the posterior strap to decrease hip abduction
. Transition immediately to a rigid hip abduction orthosis

Correct Answer & Explanation

. Continue the Pavlik harness and reassure the mother

Explanation

Femoral nerve palsy is a known complication of excessive hip flexion in a Pavlik harness. The harness must be discontinued to allow for nerve recovery before resuming any abduction treatment.

Question 859

Topic: Pediatric Hip

An 18-month-old requires open reduction for a chronically dislocated hip due to DDH. Which of the following anatomical structures is considered an intra-articular obstacle to successful closed reduction?

. Iliopsoas tendon
. Adductor longus muscle
. Transverse acetabular ligament
. Anterior joint capsule
. Reflected head of the rectus femoris

Correct Answer & Explanation

. Iliopsoas tendon

Explanation

Intra-articular obstacles to reduction in DDH include the transverse acetabular ligament, ligamentum teres, pulvinar, and an inverted limbus. Extra-articular obstacles include the iliopsoas, adductors, and an hourglass constriction of the capsule.

Question 860

Topic: Pediatric Hip

A 4-week-old female born breech undergoes an ultrasound screening for DDH. The report notes an alpha angle of 45 degrees and a beta angle of 65 degrees. According to Graf's classification, what does the alpha angle represent?

. Cartilaginous roof coverage
. Bony roof coverage
. Femoral head sphericity
. Acetabular anteversion
. Femoral neck-shaft angle

Correct Answer & Explanation

. Cartilaginous roof coverage

Explanation

In the Graf ultrasound method, the alpha angle measures the bony roof of the acetabulum (normal is > 60 degrees). The beta angle measures the cartilaginous roof.

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