Recurrence of hip instability after reconstructive surgery in patients with cerebral palsy

Background: Hip instability can cause major problems in children with cerebral palsy, although good outcomes of hip reconstructive surgery for hip instability have been reported. In the present study, we investigated the recurrence of hip instability after reconstructive surgery and the factors influencing this recurrence in patients with cerebral palsy.

Methods: We examined consecutive patients with hip instability related to cerebral palsy who had undergone hip reconstructive surgery including femoral varus derotational osteotomy. The neck-shaft angle, head-shaft angle, and migration percentage were measured at each postoperative follow-up evaluation. For each Gross Motor Function Classification System (GMFCS) level, annual changes in radiographic indices were adjusted for multiple factors with use of a linear mixed model, with sex as the fixed effect and laterality and each subject as the random effects.

Results: A total of 144 hips (seventy-six patients) were included in this study, and 845 radiographs were evaluated. The GMFCS level was II or III for twelve patients, IV for thirty, and V for thirty-four. The neck-shaft angle showed no significant change in the patients with GMFCS level II or III (p = 0.425), IV (p = 0.106), or V (p = 0.972). The head-shaft angle showed a significant change in those with GMFCS level IV (p = 0.008) but not in those with level II or III (p = 0.201) or V (p = 0.591). The migration percentage did not change significantly in patients with GMFCS level II or III (p = 0.742), but it increased significantly by 2.0% per year (p 0.001) in patients with GMFCS level IV and by 3.5% per year (p = 0.003) in those with level V.

Conclusions: Periodic monitoring and follow-up for the recurrence of hip instability is important in patients with cerebral palsy and a GMFCS level of IV or V.

Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.