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 1081
Topic: Pediatric Hip
A 6-week-old female infant is diagnosed with a dislocated left hip that is reducible on Ortolani maneuver. A Pavlik harness is initiated. At the 4-week follow-up, ultrasound reveals the left hip remains persistently dislocated in the harness. What is the most appropriate next step in management?
Correct Answer & Explanation
. Discontinue the Pavlik harness and transition to a rigid abduction orthosis
Explanation
If a dislocated hip fails to reduce after 3 to 4 weeks in a Pavlik harness, it must be discontinued to prevent "Pavlik harness disease" (erosion of the posterior acetabulum). Transitioning to a rigid abduction orthosis (e.g., Ilfeld brace) or proceeding with closed reduction and spica casting are the standard next steps.
Question 1082
Topic: Pediatric Hip
A 13-year-old obese boy presents with acute-on-chronic right groin pain and an inability to bear weight after a minor trip. Radiographs show a severe slipped capital femoral epiphysis (SCFE). Which of the following factors represents the most significant risk for the development of avascular necrosis (AVN) in this patient?
Correct Answer & Explanation
. The clinical inability to bear weight
Explanation
The inability to bear weight defines an unstable SCFE according to the Loder classification. Unstable slips have a dramatically higher risk of developing avascular necrosis (up to 47%) compared to stable slips, regardless of the slip angle severity.
Question 1083
Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Radiographs reveal greater than 50% loss of height in the lateral portion of the capital femoral epiphysis. According to the Herring lateral pillar classification, which group does this represent, and what is the typical prognosis?
Correct Answer & Explanation
. Group C; poor prognosis
Explanation
Herring Group C is defined by >50% collapse of the lateral pillar height. Patients in Group C generally have poor outcomes, and surgical containment often does not significantly alter the natural history of the severe disease.
Question 1084
Topic: Pediatric Hip
A 12-year-old boy with obesity presents with a stable slipped capital femoral epiphysis (SCFE). He undergoes in situ single-screw fixation. Which of the following is the most significant predictor of avascular necrosis (AVN) in this patient?
Correct Answer & Explanation
. Instability of the slip prior to surgery
Explanation
The most significant risk factor for AVN in SCFE is the stability of the slip at presentation. Unstable SCFEs (inability to bear weight) have an AVN rate of up to 47%, compared to nearly 0% in stable SCFEs.
Question 1085
Topic: Pediatric Hip
A 6-week-old female infant with a completely dislocated, irreducible left hip (developmental dysplasia of the hip) has been treated in a Pavlik harness for 4 weeks. Ultrasound shows no improvement, and the hip remains dislocated. What is the most appropriate next step?
Correct Answer & Explanation
. Transition to a rigid abduction orthosis
Explanation
If a Pavlik harness fails to reduce a dislocated hip after 3 to 4 weeks, it should be discontinued to prevent Pavlik harness disease (posterior acetabular wear). The next step is a trial of a rigid abduction orthosis (e.g., Ilfeld or von Rosen splint) or closed reduction and spica casting.
Question 1086
Topic: Pediatric Hip
An 8-year-old boy is diagnosed with Legg-Calve-Perthes disease. According to the lateral pillar (Herring) classification, his radiograph demonstrates >50% loss of height in the lateral third of the capital femoral epiphysis. Which of the following describes his classification and prognosis?
Correct Answer & Explanation
. Lateral Pillar C; outcomes are poor regardless of treatment
Explanation
A lateral pillar height loss of >50% corresponds to Herring Lateral Pillar Group C. In children >8 years old, Group C hips have historically poor outcomes (stiff, non-spherical) regardless of conservative or surgical containment efforts.
Question 1087
Topic: Pediatric Hip
A 13-year-old obese male presents with acute-on-chronic slipped capital femoral epiphysis (SCFE) and undergoes urgent in situ pinning. Which of the following factors is most strongly associated with the development of avascular necrosis (AVN) in this patient?
Correct Answer & Explanation
. Instability of the slip
Explanation
The stability of the slip (the patient's ability to bear weight) is the most critical prognostic factor for AVN in SCFE. Unstable slips have a significantly higher rate of AVN compared to stable slips.
Question 1088
Topic: Pediatric Hip
A 4-week-old female is placed in a Pavlik harness for developmental dysplasia of the hip (DDH). Two weeks later, the parents report she has stopped kicking her leg on the affected side. Exam reveals decreased quadriceps activity. What is the most appropriate next step in management?
Correct Answer & Explanation
. Decrease hip flexion by loosening anterior straps or temporarily removing the harness
Explanation
Femoral nerve palsy in a Pavlik harness is typically caused by excessive hip flexion. Management involves decreasing flexion by loosening the anterior straps or temporarily removing the harness until quadriceps function returns.
Question 1089
Topic: Pediatric Hip
A 4-year-old girl presents with a painless limp and a positive Trendelenburg sign on the right. Radiographs reveal a high developmental dislocation of the right hip (DDH) with a false acetabulum and an acetabular index of 42 degrees. What is the most appropriate surgical management for this patient?
Correct Answer & Explanation
. Open reduction, femoral shortening osteotomy, and pelvic osteotomy
Explanation
In children older than 3 years with neglected DDH, the soft tissues are contracted and the acetabulum is highly dysplastic. Open reduction combined with a femoral shortening osteotomy is required to safely decompress the joint and reduce the risk of avascular necrosis. A concomitant pelvic osteotomy is necessary to adequately cover the femoral head and correct the dysplasia.
Question 1090
Topic: Pediatric Hip
When performing a total hip arthroplasty on a 45-year-old female with a Crowe Type IV (high dislocation) developmental dysplasia of the hip (DDH), which of the following intraoperative strategies is most commonly required?
Correct Answer & Explanation
. A subtrochanteric shortening osteotomy to safely bring the hip center to the true acetabulum
Explanation
In Crowe Type IV DDH, the hip is completely dislocated. Reconstructing the hip at the true anatomic center of rotation is biomechanically superior. However, bringing the femur down risks severe traction injury to the sciatic nerve. Therefore, a subtrochanteric shortening osteotomy is frequently required to place the cup in the true acetabulum while safely reducing the hip without excessive nerve tension. The femoral canal in DDH is typically narrow (stovepipe), requiring specialized stems.
Question 1091
Topic: Pediatric Hip
Which of the following patient profiles represents an absolute contraindication to metal-on-metal hip resurfacing?
Correct Answer & Explanation
. A 35-year-old female with developmental dysplasia of the hip and impaired renal function
Explanation
Impaired renal function is an absolute contraindication to metal-on-metal bearings due to the inability to clear circulating cobalt and chromium ions. Furthermore, females of childbearing age and those with DDH are generally considered poor candidates.
Question 1092
Topic: Pediatric Hip
A 14-year-old boy undergoes a surgical dislocation of the hip for treatment of severe slipped capital femoral epiphysis (SCFE). During the exposure, the surgeon must protect the primary blood supply to the femoral head. Which of the following vessels provides the predominant blood supply to the femoral head in this age group, and what is its anatomical course?
Correct Answer & Explanation
. Posterosuperior and posteroinferior retinacular branches of the medial femoral circumflex artery
Explanation
The predominant blood supply to the adult and adolescent femoral head is derived from the medial femoral circumflex artery (MFCA). Specifically, the posterosuperior and posteroinferior retinacular branches of the MFCA pierce the capsule and run along the femoral neck to enter the head. During surgical dislocation, it is vital to protect the external rotators (particularly the obturator externus) to avoid stretching or severing the MFCA, which courses between the quadratus femoris and the obturator externus.
Question 1093
Topic: Pediatric Hip
A 12-year-old overweight boy is diagnosed with a severe slipped capital femoral epiphysis (SCFE). The treating orthopedic surgeon counsels the parents on the risk of avascular necrosis. The primary blood supply to the capital femoral epiphysis in this age group is derived from the lateral epiphyseal vessels. These vessels are terminal branches of which of the following arteries?
Correct Answer & Explanation
. Medial circumflex femoral artery
Explanation
In children older than 3 to 4 years of age and adolescents, the primary blood supply to the femoral head is derived from the lateral epiphyseal artery. This artery is a terminal branch of the medial circumflex femoral artery (MCFA). The artery of the ligamentum teres (a branch of the obturator artery) provides a negligible amount of blood supply in this age group. Disruption of the MCFA or its terminal branches during a SCFE or its surgical treatment can lead to avascular necrosis.
Question 1094
Topic: Pediatric Hip
A 26-year-old ice hockey player presents with insidious onset of anterior groin pain exacerbated by hip flexion and internal rotation. Radiographs demonstrate a crossover sign and an alpha angle of 70 degrees. What is the predominant pathomorphology causing his symptoms?
Correct Answer & Explanation
. Combined Cam and Pincer impingement
Explanation
The crossover sign indicates acetabular retroversion (Pincer morphology), while an alpha angle greater than 50-55 degrees indicates femoral head-neck junction asphericity (Cam morphology). Therefore, this patient has combined Cam and Pincer impingement.
Question 1095
Topic: Pediatric Hip
An 8-year-old boy presents with a 3-month history of a painless limp and right hip stiffness. Radiographs demonstrate fragmentation of the capital femoral epiphysis. Measurements reveal that exactly 40% of the lateral pillar height is maintained. According to the Herring Lateral Pillar Classification, what group does this patient fall into, and what is the typical outcome associated with surgical containment for his age and classification?
Correct Answer & Explanation
. Group C; outcomes are generally poor, and surgical containment provides no significant benefit over non-operative care
Explanation
The Herring Lateral Pillar Classification evaluates the height of the lateral pillar of the capital femoral epiphysis during the fragmentation stage of Legg-Calvé-Perthes disease. Group A retains 100% height, Group B retains >50% height, and Group C retains <50% height. This patient has 40% height, placing him in Group C. For children 8 years of age and older with Group C hips, the prognosis is generally poor (high likelihood of Stulberg III-V outcome). Large multicenter studies have demonstrated that surgical containment (e.g., femoral or pelvic osteotomy) does not significantly improve radiographic outcomes compared to non-operative treatment in this specific subgroup.
Question 1096
Topic: Pediatric Hip
A 13-year-old obese male presents with an inability to bear weight on the right leg after a minor fall. He reports having had a mild, aching knee pain for 2 months prior to the fall. Radiographs reveal a severe posterior and inferior displacement of the proximal femoral epiphysis. If an open reduction and internal fixation via a surgical dislocation approach (modified Dunn procedure) is planned, preservation of which of the following vessels is most critical to prevent osteonecrosis of the femoral head?
Correct Answer & Explanation
. Deep branch of the medial circumflex femoral artery
Explanation
The deep branch of the medial circumflex femoral artery (MCFA) is the primary blood supply to the femoral head in adolescents. During a modified Dunn procedure for an unstable slipped capital femoral epiphysis (SCFE), meticulous protection of the external rotator muscles and the retinacular vessels arising from the deep branch of the MCFA is paramount to minimize the high risk of avascular necrosis.
Question 1097
Topic: Pediatric Hip
A 6-week-old female is being treated with a Pavlik harness for a dislocated left hip. At the 2-week follow-up, an ultrasound confirms the hip remains dislocated. The examiner also notes that the infant has decreased spontaneous extension of the left knee, though she vigorously kicks the right leg. What is the most likely cause of this new clinical finding?
Correct Answer & Explanation
. Femoral nerve palsy from hyperflexion
Explanation
Femoral nerve palsy is a well-documented complication of the Pavlik harness, typically caused by hyperflexion of the hip which compresses the nerve against the inguinal ligament. It presents as decreased active knee extension. When this occurs, or if the hip fails to reduce after 3-4 weeks of harness wear, the harness must be discontinued to prevent further nerve damage and 'Pavlik harness disease' (excoriation, dysplasia, or AVN).
Question 1098
Topic: Pediatric Hip
An 8-year-old boy presents with a limp and right hip pain of several months' duration. Radiographs demonstrate sclerosis and early fragmentation of the proximal femoral epiphysis. Which of the following is considered the most significant prognostic factor for the development of early osteoarthritis in patients with this condition?
Correct Answer & Explanation
. Age at clinical onset
Explanation
Age at clinical onset is the single most important prognostic factor in Legg-Calvé-Perthes disease. Children who present at an older age (typically defined as > 8 years) have less remaining growth potential for femoral head remodeling, leading to an increased risk of permanent aspherical deformity (coxa magna) and subsequent early-onset osteoarthritis. A Gage sign is a radiographic 'head at risk' sign, but age remains the primary prognostic determinant.
Question 1099
Topic: Pediatric Hip
A 9-year-old boy presents with left knee pain and an obligatory external rotation of the left lower extremity with hip flexion. Radiographs demonstrate a severe, chronic slipped capital femoral epiphysis (SCFE) on the left. The patient's medical history is significant for chronic kidney disease and secondary hyperparathyroidism. Following in situ pinning of the left hip, what is the most appropriate management for the asymptomatic right hip?
Correct Answer & Explanation
. Prophylactic in situ percutaneous pinning
Explanation
The patient has a known endocrinopathy/metabolic disorder (renal osteodystrophy with secondary hyperparathyroidism), which places him at an exceptionally high risk for developing a contralateral slipped capital femoral epiphysis (SCFE). Prophylactic prophylactic in situ percutaneous pinning of the contralateral hip is strongly indicated in patients with underlying endocrinopathies, radiation therapy history, and in very young patients (typically less than 10 years old) presenting with a unilateral SCFE. Observation is appropriate for older, idiopathic cases, but not for this high-risk patient.
Question 1100
Topic: Pediatric Hip
An 8-year-old boy is diagnosed with Legg-Calvé-Perthes disease of the right hip. Which of the following radiographic findings is considered the most significant poor prognostic indicator, predictive of a poor long-term outcome (Stulberg class IV or V)?
Correct Answer & Explanation
. Lateral subluxation of the femoral head with hinge abduction
Explanation
In Legg-Calvé-Perthes disease, lateral subluxation of the femoral head out of the acetabulum leads to hinge abduction, where the extruded, enlarged femoral head impinges on the lateral acetabular margin during abduction. This causes severe mechanical damage, failure of the head to remodel concentrically, and a poor long-term outcome (Stulberg IV or V). An intact lateral pillar (>50% height, Herring A or B) is a good prognostic sign. The crescent sign and metaphyseal cysts are diagnostic and part of the staging but are not the primary drivers of mechanical failure compared to loss of containment and lateral subluxation.
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