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 1161
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 1162
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 1163
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 1164
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 1165
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 1166
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 1167
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 1168
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 1169
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 1170
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 1171
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 1172
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 1173
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 1174
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.
Question 1175
Topic: Pediatric Hip
A 48-year-old female with bilateral Crowe Type IV developmental dysplasia of the hip (DDH) is undergoing a primary total hip arthroplasty. The preoperative plan is to place the acetabular component in the anatomic true acetabulum. The femoral head is currently dislocated 6 cm superior to the true acetabulum. Which adjunctive surgical technique is most critical to perform during this reconstruction to avoid a devastating postoperative neurologic complication?
Correct Answer & Explanation
. A subtrochanteric femoral shortening osteotomy
Explanation
In Crowe Type IV DDH, the hip is completely dislocated superiorly. Restoring the hip center to the anatomic (true) acetabulum will require significant lengthening of the leg (in this case, >4-5 cm). This acute lengthening places profound stretch on the sciatic nerve, risking severe and potentially irreversible palsy. To prevent this, a subtrochanteric shortening osteotomy is typically necessary to safely reduce the hip without excessively stretching the sciatic nerve.
Question 1176
Topic: Pediatric Hip
A 45-year-old woman with Crowe type IV developmental dysplasia of the hip (DDH) is undergoing total hip arthroplasty. The femoral head is completely dislocated superiorly. During reconstruction, the surgeon intends to place the acetabular component in the true acetabulum. To safely reduce the hip and mitigate the risk of neurologic injury, which of the following surgical adjuncts is most frequently required?
Correct Answer & Explanation
. Femoral shortening subtrochanteric osteotomy
Explanation
In Crowe IV DDH, the hip has been dislocated superiorly for decades, leading to severe soft tissue contracture. Placing the cup in the true anatomic acetabulum requires bringing the femur down a significant distance. Attempting to reduce the hip without shortening the femur places excessive tension on the sciatic nerve. A subtrochanteric shortening osteotomy is frequently required to safely reduce the joint and prevent stretch-induced sciatic nerve palsy.
Question 1177
Topic: Pediatric Hip
A 13-year-old obese male presents with a 2-week history of right groin and knee pain. He walks with a noticeable limp but is able to bear weight. Physical examination reveals obligatory external rotation of the hip with passive flexion. Radiographs confirm a mild Slipped Capital Femoral Epiphysis (SCFE) (Figure 15). Following in situ single-screw fixation of the right hip, what is the primary clinical rationale for considering prophylactic fixation of the contralateral hip?
Correct Answer & Explanation
. To address a known 20-40% risk of contralateral slip, particularly in high-risk patients
Explanation
Patients presenting with a unilateral SCFE have a significant risk (approximately 20-40%) of developing a subsequent contralateral slip. This risk is notably higher in specific populations, including younger patients (<10 years for boys), obese patients, and those with underlying endocrinopathies (e.g., hypothyroidism). Prophylactic fixation is often discussed and implemented in these high-risk groups to prevent future displacement and the associated severe morbidity.
Question 1178
Topic: Pediatric Hip
Figure 2 shows the pelvis radiograph of a 45-year-old female with severe bilateral hip pain secondary to neglected developmental dysplasia of the hip (DDH).
She is planned for a primary right THA. The templating indicates a Crowe IV dislocation. To restore the hip's center of rotation to the true acetabulum without causing a nerve palsy, which surgical adjunct is most likely required?
Correct Answer & Explanation
. Subtrochanteric shortening osteotomy
Explanation
Crowe Type IV DDH is characterized by a completely dislocated femoral head (>100% subluxation) with a false acetabulum formed high on the ilium. To restore normal biomechanics and leg length, the acetabular component should ideally be placed in the true acetabulum. However, pulling the femur down to this level risks stretching the sciatic nerve, potentially causing a stretch neuropraxia. Most authors recommend a subtrochanteric shortening osteotomy if the required distal translation of the femur exceeds 4 cm, mitigating the risk of sciatic nerve injury.
Question 1179
Topic: Pediatric Hip
A 13-year-old obese boy with an open triradiate cartilage undergoes in-situ pinning for a stable, moderate slipped capital femoral epiphysis (SCFE) using a single cannulated screw. Six months postoperatively, he complains of severe, unrelenting global hip pain and marked stiffness. Radiographs demonstrate a sudden, severe narrowing of the joint space. What is the most likely diagnosis?
Correct Answer & Explanation
. Chondrolysis
Explanation
Chondrolysis is a devastating complication of SCFE characterized by acute onset of severe pain, marked limitation of motion (stiffness), and rapid loss of articular cartilage space (typically > 50% loss or joint space < 3 mm) on radiographs. While it can occur idiopathically in SCFE, it is strongly associated with unrecognized intra-articular pin penetration. Osteonecrosis (AVN) is more commonly associated with unstable SCFEs and typically presents with segmental collapse and sclerosis, rather than acute global joint space loss.
Question 1180
Topic: Pediatric Hip
A 6-week-old female infant is diagnosed with developmental dysplasia of the hip. Ultrasound confirms a completely dislocated but reducible left hip. She is treated with a Pavlik harness. After 3 weeks of strict harness wear, a repeat ultrasound reveals that the left hip remains persistently dislocated. What is the most appropriate next step in management?
Correct Answer & Explanation
. Abandon the Pavlik harness and transition to a rigid abduction orthosis or perform a closed reduction and spica casting
Explanation
If a dislocated hip fails to reduce after 3 to 4 weeks of appropriate Pavlik harness wear, the harness must be abandoned. Prolonged use of the harness with a persistently dislocated hip can lead to 'Pavlik harness disease,' causing damage to the posterior lip of the acetabulum, worsening dysplasia, and increasing the risk of avascular necrosis. The next appropriate step is typically a trial of a rigid abduction orthosis (e.g., Ilfeld splint) or moving directly to a closed reduction and spica casting under anesthesia.
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