This practice set contains high-yield board review questions covering key concepts in 4. Pediatrics. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 3461
Topic: 4. Pediatrics
A 7-year-old child with spastic diplegic cerebral palsy presents with a worsening crouch gait. Which of the following prior surgical interventions is the most common iatrogenic cause of this specific gait abnormality?
Correct Answer & Explanation
. Over-lengthening of the Achilles tendons
Explanation
Iatrogenic crouch gait in patients with spastic diplegia is frequently caused by over-lengthening of the heel cords. This weakens the plantarflexion-knee extension couple, causing the tibia to fall forward and the knee to flex excessively during the stance phase.
Question 3462
Topic: Pediatric Upper Extremity & Spine
A 13-year-old premenarchal girl presents for evaluation of a spinal deformity. Radiographs reveal a right thoracic adolescent idiopathic scoliosis (AIS) curve measuring 35 degrees. Her Risser stage is 0. What is the most appropriate management?
Correct Answer & Explanation
. Thoracolumbosacral orthosis (TLSO) bracing
Explanation
Bracing is indicated for skeletally immature patients (Risser 0-2, premenarchal) with an AIS curve between 25 and 40 degrees. A TLSO brace worn for at least 18 hours a day has been shown to significantly reduce the risk of progression to a surgical magnitude.
Question 3463
Topic: Pediatric Hip
A 45-year-old woman with Crowe type IV developmental dysplasia of the hip is undergoing a primary THA (
). During reconstruction, the true acetabulum is prepared. Which nerve is at greatest risk of injury when the femur is subsequently brought down to the true center of rotation?
Correct Answer & Explanation
. Sciatic nerve
Explanation
The sciatic nerve is at the greatest risk of stretch injury during femoral lengthening in THA for high-riding DDH (Crowe IV). To prevent this, a subtrochanteric shortening osteotomy is frequently necessitated to safely reduce the hip.
Question 3464
Topic: Pediatric Hip
A 12-year-old obese boy presents with a 3-week history of right thigh and knee pain. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE) of the right hip. Under what circumstance is prophylactic in situ pinning of the contralateral left hip most strongly indicated?
Correct Answer & Explanation
. Underlying diagnosis of renal osteodystrophy
Explanation
Prophylactic pinning of the contralateral hip in SCFE is highly recommended for patients with underlying endocrine or metabolic disorders (such as renal osteodystrophy or hypothyroidism). These conditions carry a significantly elevated risk for bilateral involvement.
Question 3465
Topic: Pediatric Hip
An 8-year-old boy is diagnosed with Legg-Calve-Perthes disease. Which of the following radiographic findings represents the greatest risk for a poor long-term outcome?
Correct Answer & Explanation
. Lateral subluxation of the femoral head
Explanation
Lateral subluxation (extrusion) of the femoral head causes it to abut the lateral acetabular margin, leading to hinge abduction. This mechanical block severely deforms the head during the healing phase, resulting in a poor long-term outcome.
Question 3466
Topic: Pediatric Hip
A 38-year-old woman with severe bilateral developmental dysplasia of the hip (DDH) is planned for THA. Radiographs show proximal migration of the femoral head with the inferomedial aspect of the femoral head articulating with the false acetabulum. The native acetabular teardrop is located 55% of the femoral head height inferiorly. Which Crowe classification best describes this hip?
Correct Answer & Explanation
. Crowe III
Explanation
The Crowe classification is based on the proximal migration of the femoral head. Proximal subluxation of 50-75% of the femoral head height (or 10-15% of the pelvic height) characterizes a Crowe III dysplasia.
Question 3467
Topic: Pediatric Hip
A 28-year-old man presents with chronic, deep groin pain exacerbated by hip flexion. An AP pelvis radiograph is obtained.
The image demonstrates the anterior wall of the acetabulum crossing lateral to the posterior wall before reaching the sourcil. What does this "crossover sign" primarily indicate?
Correct Answer & Explanation
. Acetabular retroversion
Explanation
The crossover sign on a true AP pelvis radiograph represents focal or global acetabular retroversion, a common cause of pincer-type femoroacetabular impingement. This retroverted morphology leads to anterior overcoverage and secondary labral pathology during hip flexion.
Question 3468
Topic: Pediatric Hip
A 45-year-old woman with a history of developmental dysplasia of the hip (DDH) requires a THA.
Preoperative planning reveals a Crowe Type IV completely dislocated, high-riding hip. Bringing the femoral head down to the true acetabulum will drastically increase sciatic nerve tension. What adjunctive procedure is most frequently required?
Correct Answer & Explanation
. Subtrochanteric shortening osteotomy
Explanation
In Crowe IV DDH, restoring the anatomic hip center often requires more than 3-4 cm of leg lengthening, which places the sciatic nerve at extremely high risk of traction palsy. A subtrochanteric shortening osteotomy is typically performed to protect the nerve while allowing cup placement in the true acetabulum.
Question 3469
Topic: Pediatric Hip
A 42-year-old woman with neglected bilateral developmental dysplasia of the hip presents for THA. Radiographs
demonstrate Crowe IV dysplasia with the femoral head completely dislocated superiorly. To place the acetabular cup at the true anatomical center of rotation and safely reduce the hip without causing sciatic nerve palsy, which of the following surgical adjuncts is most frequently required?
Correct Answer & Explanation
. Subtrochanteric shortening osteotomy
Explanation
In Crowe IV DDH, bringing the femur down to the true anatomical acetabulum involves significant lengthening, placing the sciatic nerve at high risk for stretch injury. A subtrochanteric shortening osteotomy allows for safe reduction while protecting neurovascular structures.
Question 3470
Topic: Pediatric Hip
Which of the following patients presenting with a unilateral slipped capital femoral epiphysis (SCFE) is at the highest risk for a contralateral slip and represents the strongest indication for prophylactic in situ pinning of the contralateral hip?
Correct Answer & Explanation
. A 10-year-old girl with primary hypothyroidism
Explanation
Patients with underlying endocrine disorders (such as hypothyroidism or renal osteodystrophy) or those who are very young (e.g., <10 years old) are at an exceptionally high risk for bilateral SCFE and are strong candidates for prophylactic contralateral pinning.
Question 3471
Topic: Pediatric Hip
Which of the following clinical profiles represents an absolute contraindication to metal-on-metal hip resurfacing?
Correct Answer & Explanation
. A 50-year-old female with chronic kidney disease (GFR < 30 mL/min)
Explanation
Metal-on-metal resurfacing relies on renal clearance of circulating cobalt and chromium ions. It is strictly contraindicated in patients with significant renal impairment, as well as in females of childbearing age or patients with large femoral head cysts.
Question 3472
Topic: Pediatric Hip
A 45-year-old woman presents with severe hip osteoarthritis secondary to developmental dysplasia of the hip (DDH). Preoperative radiographs reveal that the native femoral head is migrated superiorly, demonstrating 110% subluxation relative to the true acetabulum. What is the correct Crowe classification for this hip?
Correct Answer & Explanation
. Crowe IV
Explanation
The Crowe classification stages DDH based on the degree of proximal subluxation. Crowe I is <50%, II is 50-74%, III is 75-99%, and Crowe IV is >100% subluxation (a completely dislocated, high-riding hip).
Question 3473
Topic: Pediatric Hip
A 45-year-old woman with a history of neglected developmental dysplasia of the hip (DDH) presents with severe, debilitating osteoarthritis. Preoperative radiographs demonstrate complete dislocation of the femoral head, with proximal migration exceeding 100% of the normal vertical height of the femoral head. According to the Crowe classification, what type of dysplasia does this represent, and which surgical technique is most likely required to safely restore the hip center during THA?
Correct Answer & Explanation
. Crowe IV; subtrochanteric shortening osteotomy
Explanation
The Crowe classification stages DDH based on the degree of proximal subluxation of the femoral head relative to the teardrop. Crowe I: <50% subluxation; Crowe II: 50-74%; Crowe III: 75-100%; Crowe IV: >100% (complete dislocation). Bringing the hip center down to the true acetabulum in a Crowe IV hip often results in excessive lengthening of the limb, leading to severe stretching of the sciatic nerve and subsequent palsy. To prevent this, a subtrochanteric shortening osteotomy of the femur is frequently necessary to safely reduce the hip while protecting the neurovascular structures.
Question 3474
Topic: Pediatric Hip
Figure 7 displays the preoperative AP pelvis radiograph of a 45-year-old woman with severe bilateral developmental dysplasia of the hip (Crowe Type IV). She is planned to undergo a right total hip arthroplasty. To optimize hip biomechanics, abductor function, and component longevity, where should the acetabular component ideally be placed, and what adjunctive procedure is most likely required?
Correct Answer & Explanation
. True anatomic acetabulum with a concurrent subtrochanteric shortening osteotomy
Explanation
In Crowe Type IV developmental dysplasia of the hip (DDH), the femoral head is completely dislocated and forms a pseudoacetabulum superiorly. The standard of care for optimal biomechanics and implant longevity is to place the acetabular component at the level of the true anatomic acetabulum. Because the femur has been completely dislocated for decades, bringing the femoral head down to the true acetabulum places severe stretch on the neurovascular structures (specifically the sciatic nerve). Therefore, a subtrochanteric femoral shortening osteotomy is typically required to safely reduce the hip without causing sciatic nerve palsy.
Question 3475
Topic: Pediatric Hip
Figure 3 shows the AP pelvis radiograph of a 25-year-old woman with symptomatic developmental dysplasia of the hip (DDH) who is scheduled for a Bernese periacetabular osteotomy (PAO). During a classic PAO, which of the following pelvic structures intentionally remains intact to preserve pelvic stability and allow early mobilization?
Correct Answer & Explanation
. Posterior column
Explanation
The Bernese periacetabular osteotomy (PAO) involves a series of four osteotomies: incomplete ischial, superior pubic ramus, incomplete iliac, and retroacetabular (connecting the iliac and ischial cuts). A hallmark of the PAO, which distinguishes it from earlier osteotomies (like the single or triple innominate osteotomies), is that the posterior column of the pelvis remains intact. This preserves the inherent stability of the pelvic ring, permits early postoperative mobilization, and preserves the geometry of the true pelvis, which is important for females of childbearing age.
Question 3476
Topic: Pediatric Hip
Figure 6 displays the radiographs of a 13-year-old boy who presents with severe, progressive groin pain and stiffness 7 months after undergoing in situ percutaneous pinning for a slipped capital femoral epiphysis (SCFE). Radiographs demonstrate diffuse joint space narrowing without evidence of femoral head collapse or crescent sign. What is the most likely diagnosis?
Correct Answer & Explanation
. Chondrolysis
Explanation
The clinical presentation of increasing stiffness and pain following pinning of a SCFE, combined with classic radiographic findings of diffuse concentric joint space narrowing (< 3mm) without subchondral collapse, is diagnostic of chondrolysis. Chondrolysis is a devastating complication often associated with unrecognized intra-articular pin penetration. Avascular necrosis (AVN) would present with subchondral sclerosis, cyst formation, the crescent sign, or structural collapse of the femoral head.
Question 3477
Topic: Pediatric Hip
A 42-year-old female with a history of developmental dysplasia of the hip (DDH) requires a total hip arthroplasty. Preoperative templating reveals that her femoral head is subluxated proximally by 85% relative to the height of the normal true acetabulum. How is this classified according to the Crowe classification, and what key surgical maneuver is most likely necessary to restore the normal hip center?
Correct Answer & Explanation
. Crowe III; femoral shortening osteotomy to safely place the cup in the true acetabulum
Explanation
The Crowe classification for DDH is based on the degree of proximal subluxation: Type I (<50%), Type II (50-74%), Type III (75-100%), and Type IV (>100%). At 85% subluxation, the patient is Crowe III. Bringing the hip down to the true anatomic center of rotation often requires significant leg lengthening, posing a severe risk of sciatic nerve palsy. Therefore, a femoral shortening osteotomy (such as a subtrochanteric osteotomy) is frequently required to reduce the joint safely.
Question 3478
Topic: Pediatric Hip
A 12-year-old boy weighing 95 kg (BMI > 95th percentile) presents with a 2-week history of right thigh pain and an inability to bear weight. Radiographs confirm a severe, unstable right slipped capital femoral epiphysis (SCFE). After treating the right hip, prophylactic pinning of the asymptomatic left hip is most strongly indicated by which of the following patient factors?
Correct Answer & Explanation
. His skeletal immaturity (open triradiate cartilage)
Explanation
The risk of a contralateral slip in SCFE is closely associated with skeletal immaturity, endocrine disorders, and severe obesity. An open triradiate cartilage (assessed via the modified Oxford bone age score) is a powerful predictor of future contralateral slip, making prophylactic pinning highly recommended in such patients to prevent subsequent displacement and associated morbidity.
Question 3479
Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Radiographs show fragmentation of the femoral head with maintenance of greater than 50% of the lateral pillar height. According to the Herring classification, this is a Group B hip. Which of the following statements best describes the prognostic significance and recommended management for this patient?
Correct Answer & Explanation
. Because the child is younger than 8 years old, conservative management yields outcomes equivalent to surgery
Explanation
In Herring Group B hips (lateral pillar height >50% but <100%), age at onset is a critical prognostic factor. Children under 8 years of age at onset generally do well with conservative management, and surgical containment (e.g., pelvic or femoral osteotomy) has not been shown to significantly improve outcomes compared to nonoperative care. In contrast, children 8 years or older with Group B hips, or B/C border hips, benefit significantly from surgical containment.
Question 3480
Topic: Pediatric Hip
A 28-year-old female presents with anterior groin pain exacerbated by deep flexion and internal rotation. Radiographs demonstrate a lateral center-edge angle of 16 degrees and a Tönnis angle of 18 degrees. An MRI arthrogram reveals an anterosuperior labral tear and prominent cam morphology on the femoral neck. If this patient undergoes isolated hip arthroscopy with labral repair and femoral osteochondroplasty, what is the most likely long-term complication?
Correct Answer & Explanation
. Rapid progression of hip osteoarthritis due to microinstability
Explanation
This patient presents with frank developmental dysplasia of the hip (DDH), indicated by a lateral center-edge angle (LCEA) of less than 20 degrees (normal is >25) and a Tönnis angle greater than 10 degrees. The labrum in dysplastic hips is typically hypertrophic and acts as a primary secondary stabilizer to the deficient bony coverage. Performing an isolated hip arthroscopy with labral debridement/repair and femoral osteochondroplasty (cam resection) in a severely dysplastic hip disrupts the remaining soft-tissue static constraints (e.g., the labrum and capsule). This leads to iatrogenic microinstability, catastrophic capsular failure, and rapid acceleration of osteoarthritis. The appropriate surgical management for symptomatic DDH with secondary impingement often requires a redirectional osteotomy (such as a periacetabular osteotomy [PAO]) to correct the structural bony deficiency, sometimes combined with an arthrotomy or arthroscopy to address intra-articular pathology.
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