Asymmetric hip deformity and subluxation in cerebral palsy: an analysis of surgical treatment.

Thirty-seven cerebral palsy patients were followed with measurements of the migration index (MI), infrapelvic obliquity, and suprapelvic obliquity over a mean period of 73 months to evaluate the development of the windblown deformity. The infrapelvic asymmetry was apparent before the suprapelvic obliquity; however, 65% eventually had both. The final pattern of infrapelvic obliquity and the most subluxed hip could not be predicted from initial radiographs or from the pattern of scoliosis. Hip subluxation strongly correlated with the degree of femoral adduction and weakly with the magnitude of suprapelvic obliquity. The suprapelvic obliquity and scoliosis increased over time and influenced the final windblown appearance. Soft-tissue surgeries did not have a significant effect on the final MI. Severe abduction deformities generally followed ipsilateral adductor releases. Finally, despite improvement in the MI of the initially more subluxed hip, 33% of patients still had one hip with a MI >50%.