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 541
Topic: Pediatric Hip
A 6-month-old infant is diagnosed with a delayed presentation of developmental dysplasia of the hip (DDH). Ultrasound confirms a completely dislocated but reducible hip. What is the most appropriate initial management step?
Correct Answer & Explanation
. Closed reduction and spica cast application under general anesthesia
Explanation
For a reducible DDH at 6 months of age, closed reduction under general anesthesia (often with an arthrogram) followed by spica casting is the standard of care. A Pavlik harness is generally ineffective and poorly tolerated after 6 months of age.
Question 542
Topic: Pediatric Hip
Which of the following is the strongest indication for prophylactic pinning of the asymptomatic contralateral hip in a patient presenting with unilateral Slipped Capital Femoral Epiphysis (SCFE)?
Correct Answer & Explanation
. Underlying hypothyroidism
Explanation
Prophylactic pinning of the contralateral hip in SCFE is generally indicated in patients with underlying endocrinopathies (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency) or those undergoing radiation therapy, because their risk of developing bilateral SCFE approaches 50-100%. While obesity is a risk factor for SCFE, it alone is not an absolute indication for prophylactic pinning. Younger age (e.g., less than 10 years) or an open triradiate cartilage are also considered relative indications for prophylaxis due to the longer remaining growth and time at risk.
Question 543
Topic: Pediatric Hip
According to the Herring Lateral Pillar Classification for Legg-Calve-Perthes disease, which of the following radiographic findings defines a Lateral Pillar Group C classification?
Correct Answer & Explanation
. Less than 50% of the original lateral pillar height remains (greater than 50% collapse)
Explanation
The Herring Lateral Pillar classification assesses the height of the lateral pillar of the femoral head on an AP pelvis radiograph during the fragmentation stage of Perthes disease. Group A: No loss of height. Group B: Greater than 50% of lateral pillar height is maintained. Group C: Less than 50% of lateral pillar height is maintained (i.e., greater than 50% collapse). The B/C border group maintains exactly 50% height or has a narrow, depressed lateral pillar. Group C has the poorest prognosis.
Question 544
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 appointment, the parents report that the baby has stopped actively extending the knee on the treated side. Physical exam confirms absent active knee extension and a diminished patellar reflex. What was the most likely error in the application of the harness?
Correct Answer & Explanation
. Excessive hip flexion
Explanation
The infant has developed a femoral nerve palsy, a known complication of Pavlik harness treatment. This is typically caused by hyperflexion of the hips, which compresses the femoral nerve against the inguinal ligament or pubis. The treatment is to temporarily remove the harness or adjust the anterior straps to reduce flexion. Excessive abduction is associated with a different, severe complication: avascular necrosis (AVN) of the femoral head.
Question 545
Topic: Pediatric Hip
A 6-week-old female is diagnosed with Developmental Dysplasia of the Hip (DDH) and placed in a Pavlik harness. During a follow-up visit, the orthopaedic surgeon notes decreased spontaneous movement of the patient's knee and an absent patellar reflex on the affected side. This complication is most likely due to which of the following mechanical positioning errors in the harness?
Correct Answer & Explanation
. Excessive flexion of the hips
Explanation
The complication described is a femoral nerve palsy, which manifests as decreased active knee extension and an absent patellar reflex. In a Pavlik harness, this is classically caused by hyperflexion of the hips (typically > 120 degrees), which compresses the femoral nerve against the inguinal ligament. Excessive abduction is associated with avascular necrosis (AVN) of the femoral head.
Question 546
Topic: Pediatric Hip
A 12-year-old boy presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE) of the left hip. Prophylactic pinning of the contralateral right hip is discussed with the family. Which of the following patient factors is considered the strongest absolute indication for prophylactic fixation of the asymptomatic contralateral hip?
Correct Answer & Explanation
. Presence of an underlying endocrine disorder
Explanation
Patients with underlying endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) have an exceptionally high rate (up to 100% in some series) of developing bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly indicated in these cases. The other options are relative considerations but not as definitive as a diagnosed endocrinopathy.
Question 547
Topic: Pediatric Hip
A 10-year-old boy with a BMI in the 99th percentile and height in the 3rd percentile presents with bilateral knee pain and a waddling gait. Radiographs confirm bilateral Slipped Capital Femoral Epiphysis (SCFE). Given his age and height percentile, an endocrine workup is initiated. Which of the following is the most commonly associated endocrinopathy in this clinical scenario?
Correct Answer & Explanation
. Hypothyroidism
Explanation
Hypothyroidism is the most common endocrine disorder associated with Slipped Capital Femoral Epiphysis (SCFE). Patients with endocrine-related SCFE typically present at an atypical age (either younger than 10 or older than 16), often with short stature, and frequently have bilateral involvement. The combination of obesity and decreased height velocity strongly suggests hypothyroidism, distinguishing it from typical idiopathic SCFE where patients may be obese but are usually of normal or increased height.
Question 548
Topic: Pediatric Hip
A 3-month-old female infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During her 2-week follow-up, the mother reports that the infant is not kicking her left leg as much as the right. On examination, the infant exhibits absent active knee extension on the left side, although she withdraws to pain. Passive range of motion is full. Which of the following adjustments to the Pavlik harness is the most appropriate next step in management?
Correct Answer & Explanation
. Loosen the anterior flexion straps
Explanation
The infant is presenting with a femoral nerve palsy, a known complication of the Pavlik harness. This occurs due to excessive hyperflexion of the hip, which compresses or stretches the femoral nerve against the inguinal ligament or pelvic brim. The clinical sign is a loss of active knee extension. The appropriate management is to temporarily loosen or release the anterior flexion straps to reduce the degree of hip flexion, allowing the nerve to recover. Abandoning the harness entirely is not immediately indicated unless the palsy fails to resolve.
Question 549
Topic: Pediatric Hip
A 3-year-old girl is undergoing surgical treatment for developmental dysplasia of the hip (DDH). The surgeon performs a pelvic osteotomy that is described as an incomplete, pericapsular osteotomy that hinges on the triradiate cartilage, allowing the acetabular roof to be hinged downward to improve anterolateral coverage, thereby decreasing the volume of the acetabulum. Which osteotomy is being described?
Correct Answer & Explanation
. Pemberton osteotomy
Explanation
The Pemberton osteotomy is an incomplete transiliac osteotomy that hinges at the triradiate cartilage, altering the shape and decreasing the volume of the acetabulum. The Salter osteotomy is a complete osteotomy that hinges at the pubic symphysis without changing the acetabular volume. The Dega osteotomy also hinges at the triradiate cartilage but leaves the inner table of the ilium intact.
Question 550
Topic: Pediatric Hip
A 13-year-old boy presents with a limp and obligate external rotation of his left hip during passive flexion, indicative of a slipped capital femoral epiphysis (SCFE). Relative to the capital femoral epiphysis, in what direction does the femoral neck (metaphysis) displace in a typical SCFE?
Correct Answer & Explanation
. Posterior and inferior
Explanation
In a SCFE, the capital femoral epiphysis remains secured within the acetabulum while the femoral metaphysis (neck) displaces anteriorly and superiorly. This gives the radiographic appearance that the epiphysis has slipped posteriorly and inferiorly.
Question 551
Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. During the radiographic evaluation of the hip, the earliest sign of the fragmentation stage represents a subchondral fracture of the femoral head. What is the eponym or term for this specific radiographic finding?
Correct Answer & Explanation
. Crescent sign
Explanation
The 'crescent sign' in Legg-Calvé-Perthes disease (or avascular necrosis) represents a subchondral fracture and marks the beginning of the fragmentation stage. Waldenström's sign is an increase in the medial joint space seen very early. Trethowan's sign and Klein's line are associated with SCFE. The sagging rope sign is a late sign indicating a widened femoral neck and coxa magna.
Question 552
Topic: Pediatric Hip
A 7-year-old girl with a history of neglected Developmental Dysplasia of the Hip (DDH) presents with a severely subluxated, incongruent hip joint. The acetabulum is extremely shallow and unable to adequately cover the femoral head using redirectional techniques. The surgeon decides to perform a salvage pelvic osteotomy that relies on the interposition of the joint capsule to provide coverage and medialize the hip center of rotation. Which of the following procedures is planned?
Correct Answer & Explanation
. Chiari osteotomy
Explanation
The Chiari osteotomy is a salvage procedure used for incongruent hips where the femoral head cannot be concentrically reduced. It involves an iliac osteotomy just above the acetabulum, with the distal fragment displaced medially. The interposed joint capsule undergoes metaplasia to form a fibrous weight-bearing surface (fibrocartilage). Salter, Pemberton, Dega, and Ganz are all reconstructive (redirectional or reshaping) osteotomies requiring a congruent hip joint.
Question 553
Topic: Pediatric Hip
In a patient presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE), which of the following risk factors is the strongest clinical indication for performing a prophylactic in situ pinning of the asymptomatic contralateral hip?
Correct Answer & Explanation
. Presence of an underlying endocrinopathy (e.g., hypothyroidism)
Explanation
Prophylactic pinning of the contralateral hip in SCFE is controversial but is widely recommended and strongly indicated in patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), as their risk of developing a contralateral slip can exceed 50-100%.
Question 554
Topic: Pediatric Hip
A 12-year-old boy is diagnosed with a stable left Slipped Capital Femoral Epiphysis (SCFE). Which of the following patient characteristics is an absolute indication for prophylactic in-situ pinning of the contralateral asymptomatic right hip?
Correct Answer & Explanation
. Presence of an underlying endocrine disorder
Explanation
While there is debate regarding routine prophylactic pinning in idiopathic SCFE, the presence of an underlying endocrine disorder (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or prior radiation therapy is an absolute indication for prophylactic pinning of the contralateral hip due to a remarkably high rate (up to 50-100%) of bilateral involvement.
Question 555
Topic: Pediatric Hip
A 3-year-old girl is diagnosed with a neglected left Developmental Dysplasia of the Hip (DDH). Radiographs confirm a completely dislocated, high-riding femoral head with a false acetabulum. What is the most appropriate surgical management?
Correct Answer & Explanation
. Open reduction with a femoral shortening osteotomy and pelvic osteotomy
Explanation
In older children (typically > 2-3 years) with neglected, high-riding DDH, open reduction alone carries an unacceptably high rate of avascular necrosis (AVN) due to severe soft tissue tension. A femoral shortening osteotomy is required to reduce the tension on the hip joint, and a concomitant pelvic osteotomy (e.g., Salter or Pemberton) is almost always necessary to correct the underlying severe acetabular dysplasia.
Question 556
Topic: Pediatric Hip
A 12-year-old obese male is diagnosed with a unilateral left Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the strongest indication for prophylactic pinning of the asymptomatic right hip?
Correct Answer & Explanation
. Underlying endocrine disorder
Explanation
Prophylactic pinning of the contralateral hip in SCFE is controversial for idiopathic cases but is strongly indicated in patients with underlying endocrine disorders (e.g., hypothyroidism, panhypopituitarism, renal osteodystrophy) or prior radiation therapy, as they have a near 100% risk of bilateral involvement.
Question 557
Topic: Pediatric Hip
In the Herring Lateral Pillar Classification of Legg-Calvé-Perthes disease, a Group B hip is defined by what percentage of lateral pillar height maintenance on an AP radiograph during the fragmentation stage?
Correct Answer & Explanation
. < 50%
Explanation
The Herring Lateral Pillar classification divides Perthes disease into three main groups based on the height of the lateral pillar of the capital femoral epiphysis. Group A has no involvement (100% height maintained). Group B has > 50% of the lateral pillar height maintained. Group C has < 50% height maintained.
Question 558
Topic: Pediatric Hip
What is the most significant risk factor for the development of avascular necrosis (AVN) of the femoral head following a slipped capital femoral epiphysis (SCFE)?
Correct Answer & Explanation
. Instability of the slip (inability to bear weight)
Explanation
The Loder classification divides SCFE into stable (able to bear weight with or without crutches) and unstable (unable to bear weight). Unstable SCFE has a significantly higher rate of avascular necrosis (AVN), ranging from 20% to 50%, compared to stable SCFE which has an AVN rate of nearly 0%.
Question 559
Topic: Pediatric Hip
A 4-month-old infant is placed in a Pavlik harness for the treatment of developmental dysplasia of the hip (DDH). Which of the following positions or strap adjustments places the infant at the highest risk for developing avascular necrosis (AVN) of the femoral head?
Correct Answer & Explanation
. Excessive hip abduction by over-tightening the posterior straps
Explanation
Excessive abduction in a Pavlik harness places the hip at high risk for avascular necrosis (AVN) due to occlusion of the retinacular vessels against the acetabular rim. Excessive hip flexion places the infant at risk for femoral nerve palsy.
Question 560
Topic: Pediatric Hip
A 12-year-old obese male undergoes in-situ single screw fixation for a stable slipped capital femoral epiphysis (SCFE). Which of the following technical errors or clinical factors is most strongly associated with the development of postoperative chondrolysis?
Correct Answer & Explanation
. Unrecognized intra-articular penetration by the hardware
Explanation
Chondrolysis is a devastating complication of SCFE characterized by acute loss of articular cartilage space. The most strongly associated iatrogenic cause is unrecognized intra-articular hardware penetration during pinning. To prevent this, the 'approach-withdraw' technique under fluoroscopy must be used to ensure the screw tip is fully within the epiphysis.
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