O2120: Mid-term Outcomes and Predictors of Failure After Surgical Hip Dislocation with Femoral Head Reshaping and Relative Neck Lengthening for Symptomatic Residual Deformity in Legg-calvé-perthes Disease

Background: Legg-Calve-Perthes disease (LCPD) is an idiopathic osteonecrosis of the immature femoral head that often causes substantial joint deformity. Treatment for the LCPD-related residual deformity usually involves the surgical hip dislocation (SHD) approach. Prior studies have shown short-term clinical and functional improvements in SHD with concomitant procedures for treating LCPD deformity. However, most published studies are limited to early findings with short-term follow-up. It is unclear from the literature whether SHD retains hip function, preserves the native hip, and avoids total hip arthroplasty (THA) in the intermediate and long term. In this study, patients with residual hip deformity after healed LCPD, who underwent a SHD with femoral head and neck reshaping and relative femoral neck lengthening, were followed for at least four years and were evaluated with hip-specific outcome scores.

Methods: This is a retrospective study of 60 patients who underwent a SHD from 2000-2013 for the treatment of symptomatic residual LCPD deformity. Fifty-one (85%) patients (mean age 16.3 years), were followed 4 years or more after surgery. Demographic data, patient-reported outcomes, and radiographic measures were collected. Failure was defined as either conversion to or recommendation for THA or a WOMAC pain score ≥10 at the most recent follow-up. A multivariable cox proportional hazards model was used to identify factors predictive of failure. Hip survival was estimated using a Kaplan-Meier curve.

Results: Twenty (39%) patients met one of the endpoint criteria for surgical failure and 31 (61%) patients had their hips preserved at a median follow-up of 10.2 years (IQR, 5.7 to 12.9 years). The estimated survival was 80% (95%CI=70-92%) at 5 years and 66% (95%CI=53-81%) at 10 years.

The failure group had significantly greater pre-operative and post-operative WOMAC pain, stiffness, and function compared to the non-failure group (all p< 0.01). For both groups, deformity measured by articulo-trochanteric distance (ATD) and alpha angle on AP radiograph improved significantly from pre-op to post-op (both p< 0.05). The following also improved significantly for the non-failure group: deformity measured by lateral center edge angle (LCEA), WOMAC pain and stiffness.

Independent factors associated with surgical failure were the severity of the deformity assessed by the AP alpha angle (HR=1.06; 95%CI=1.01-1.11; p=0.01) and the severity of preoperative pain assessed by WOMAC pain score (HR=1.16; 95%CI=1.03-1.30; p=0.01).

There were no significant differences in age at SHD, sex, laterality, BMI, or previous treatment between the failure and non-failure groups.

Conclusion: SHD improves pain, stiffness, function, and deformity severity in patients with healed LCPD, and the majority of hips survive beyond 10 years.

The decision to perform the SHD procedure must consider the severity of preoperative deformity assessed by AP alpha angle and the intensity of preoperative pain assessed by WOMAC pain score, both of which are independently associated with surgical failure.