Pediatric Hip Deformity: Comprehensive Diagnosis & Management of Legg-Calvé-Perthes Sequelae
Key Takeaway
Diagnosing complex pediatric hip deformities due to LCPD sequelae requires a thorough clinical exam for restricted ROM and gait issues. Advanced imaging, like X-rays and CT, is crucial for identifying specific deformities such as coxa vara, cam impingement, and femoral retroversion, vital for precise treatment planning.
You are reviewing this 10-year-old patient in clinic. The family is concerned about his ongoing pain and worsening limp. Based on the radiographs provided, how would you classify this hip, and what are the specific anatomical features that define this classification and guide your surgical management?
Candidate: I would classify this as Stulberg Group IV LCPD sequelae. The femoral head is flattened and incongruent. He has coxa vara with a neck-shaft angle of 110 degrees, reduced head-neck offset indicating a cam-type impingement, and some lateral subluxation. I would consider a valgus-flexion osteotomy to improve coverage and rotation.
Candidates often focus only on the "flat head." A poor answer ignores the quantitative metrics (EPI, Alpha angle, Neck-shaft angle) and fails to address the "why" of the surgery (i.e., failing to link the retroversion and abductor lever arm deficiency to the clinical Trendelenburg gait and restricted rotation).
This is a Stulberg IV hip characterized by asphericity and incongruency. Key features: 1) Coxa vara (NSA 110°) reducing the abductor lever arm (Trendelenburg gait); 2) Femoral retroversion causing restricted internal rotation and impingement; 3) Cam-type deformity (Alpha angle 75°) and 4) Lateral extrusion (EPI 35%). My goal for a valgus-flexion-derotation osteotomy is to restore the abductor mechanism, center the femoral head (improving lateral coverage), and re-orient the femoral neck to eliminate impingement during flexion and internal rotation.
You have decided to perform a proximal femoral osteotomy. How do you ensure you achieve the correct degree of derotation intra-operatively to treat the retroversion identified on CT?
Candidate: I would use K-wires as markers in both the proximal and distal fragments. I would measure the rotation before the cut and then manually rotate the distal fragment by the calculated 25-30 degrees relative to the proximal fragment before fixing it with the blade plate.
Failing to mention the "reference" point. A weak answer relies on visual estimation ("eye-balling the rotation"), which is highly inaccurate in hip osteotomies. Candidates must emphasize the use of objective markers (K-wires) and clinical validation.
I would use a two-wire technique for rotational control: one K-wire placed in the proximal neck/head segment and a second in the distal femoral shaft. I would then use a sterile goniometer or a pre-measured jig to rotate the distal fragment by the specific degree required based on pre-operative templating. Finally, I would perform a dynamic intra-operative assessment of the range of motion—specifically checking for the restoration of internal rotation and the absence of impingement—before final plate fixation.
The surgery goes well, but at 12 months post-op, the patient is still demonstrating a subtle Trendelenburg gait despite radiographic union. What adjunctive procedure might you have considered at the time of the index surgery to address this, and why?
Candidate: I would consider a greater trochanteric advancement. This would help by lengthening the abductor lever arm, which is often compromised in Perthes sequelae due to relative trochanteric overgrowth.
Missing the mechanical relationship between the trochanter and the acetabular rim. Simply saying "it helps the gait" is insufficient; the candidate must mention trochanteric-pelvic impingement.
In LCPD sequelae, relative overgrowth of the greater trochanter creates two problems: 1) a mechanical impingement against the ilium during abduction, and 2) a reduction in the abductor lever arm efficiency. A greater trochanteric distal advancement (osteotomy) addresses both by lowering the insertion point, effectively tensioning the gluteus medius and alleviating the mechanical block against the pelvis. This is a crucial adjunct to the femoral osteotomy to optimize functional gait outcomes.
