Adductor surgery to prevent hip displacement in children with cerebral palsy: the predictive role of the Gross Motor Function Classification System.

The purpose of this study was to evaluate the relationship between walking ability, as determined with use of the Gross Motor Function Classification System (GMFCS), and the outcome of hip adductor surgery used to prevent hip displacement in children with cerebral palsy. We performed a retrospective review of the records of all children with cerebral palsy whose index surgery, performed between January 1994 and December 2004 at one tertiary-level pediatric hospital, was bilateral hip adductor releases. All children had a hip migration percentage of >30% in at least one hip prior to the adductor surgery, and the minimum duration of follow-up was twenty-four months. Kaplan-Meier survivorship curves were generated by determining the time from the index surgery to "failure," defined as either the need for subsequent surgical procedures or a migration percentage of ≥50% in either hip. Hazard ratios were calculated for sex, migration percentage at the time of the index surgery, age at the time of the index surgery, and GMFCS level. Three hundred and thirty children were included in the study; 73% (242) were nonambulatory (GMFCS level IV or V). The mean age at the time of the index surgery was 4.2 years, the mean migration percentage was 43%, and the mean duration of postoperative follow-up was 7.1 years. Surgery consisted of open lengthening of the adductor longus and gracilis muscles in all children, with additional procedures as deemed necessary. "Success" was defined as the absence of subsequent surgical procedures during the study period and a migration percentage of <50% in both hips at the time of follow-up. One hundred and six children (32%) met these criteria for success. The success rate was 94% (thirty-one of thirty-three) in children at a GMFCS level of II, 49% (twenty-seven of fifty-five) in children at a level of III, 27% (twenty-eight of 103) in children at a level of IV, and 14% (twenty of 139) in children at a level of V. Walking ability, as defined with use of the GMFCS level, is a strong predictor of success or failure after hip adductor surgery in children with cerebral palsy. The paradox of hip adductor surgery for children with cerebral palsy is that the children who are most severely affected and need the surgery the most have the poorest results.