Radiographic and patient-specific predictors of poor outcome following hip reconstruction in children with cerebral palsy

Patients with spastic cerebral palsy (CP) are at a high risk of neurogenic hip dysplasia/subluxation depending on the severity of the neuromuscular disorder. Untreated, approximately one third of all patients develop hip dislocation. Reconstruction with femoral varus derotational osteotomy (VDRO) combined with Dega acetabuloplasty (PO) represents the gold standard. The goal of this study was the radiographic assessment after reconstructive treatment of spastic hip dysplasia/(sub)luxation and to derive specific thresholds and target values of neck shaft angle NSA) and femoro-epiphyseal acetabular roof (FEAR)-index that could be beneficial in predicting long-term outcome. In this retrospective evaluation, 121 patients (224 hips) with CP who underwent VDRO/acetabuloplasty were grouped according to their age at surgery and postoperative radiographic parameters (NSA and FEAR-index) and compared with each other over time (5-year follow-up). The preoperative, postoperative and follow-up X-rays were analyzed. For this purpose, the FEAR, lateral center-edge angle (LCE) and migration percentage (MP) were analyzed as outcome measures at hip-level using linear mixed models (LMM). Patients older than 8 years and with a postoperative FEAR > -20° or a postoperative NSA > 130° showed a significantly worse postoperative result (FEAR, LCE and MP). A deterioration of the outcome parameters was found in all subgroups to approximately the same extent up to 2 years postoperatively. After 5 years, the findings remained stable. Failure rates and relative risks of inferior subgroups (FEAR-index ≥-20°, NSA ≥ 130°, age ≥ 8 years) were approximately twice as high (nAGE 18/114 vs. 34/110; nFEAR 20/150 vs. 25/74; nNSA 22/132 vs. 27/92). A sufficient postoperative head coverage/reduction of MP and thus joint stability is crucial for long-term outcomes after VDRO and PO. Particularly the FEAR-index seems to be a useful parameters for the surgeon for preoperative planning and postoperative aftercare. If postoperative risk factors are present, an individualized aftercare program and hip monitoring plan that establishes more frequent postoperative assessment and possible prolonged abduction therapy should be considered.