Unilateral hip reconstruction in children with cerebral palsy: predictors for failure.

Background: Unilateral hip reconstruction in patients with cerebral palsy can be complicated by contralateral subluxation and ipsilateral failure. We sought to identify predictors for failure after unilateral reconstruction in patients with GMFCS IV-V CP with unilateral hip involvement. Methods: We performed an IRB-approved retrospective study on GMFCS IV-V CP patients with unilateral hip reconstruction at a minimum 2-year follow-up. Radiologic data included acetabular index, femoral migration index (FMI), lateral center edge angle (LCE), and pelvic obliquity. The effects of age, sex, pelvic obliquity, scoliosis surgery, and contralateral hip soft-tissue release at the index surgery were analyzed for ipsilateral hip failure and contralateral hip subluxation. Statistical analysis was performed using the chi(2) and t tests. Results: There were 35 patients (M: F, 23: 12) with mean age of 110 months (range, 45 to 215 mo) with mean follow-up of 60.5 months (range, 24 to 129 mo). The mean preoperative ipsilateral hip FMI was 60% (range, 40% to 100%) and the mean LCE was -16.7 degrees (range, -85 to 17.2 degrees). Contralateral soft-tissue release was performed in 13/35 patients. Ipsilateral hip failure or contralateral hip subluxation was observed in 51% (18/35) patients. Contralateral hip subluxation developed in 28% (10/35) of patients. Ipsilateral hip failure was observed in 34% (12/35) patients. Four had both ipsilateral failure and contralateral subluxation. Lack of contralateral hip soft-tissue release, reversal of pelvic obliquity angle, and high initial contralateral hip FMI (>25%) significantly predicted the risk of contralateral hip subluxation (P=0.03). Similarly, persistence or worsening of preoperative pelvic obliquity significantly predicted ipsilateral hip failure (P<0.04). There was a strong trend toward contralateral hip subluxation in patients below 8 years of age (P=0.1) and ipsilateral hip failure in those who had spinal fusion surgery for scoliosis (P=0.06). Conclusions: Predictors of contralateral hip subluxation included lack of contralateral soft-tissue release, reversal of pelvic obliquity angle, and larger initial contralateral hip FMI (>25%). The only predictor of ipsilateral failure was persistence or worsening of preoperative pelvic obliquity.