Preoperative hip rotation moments do not predict long-term development after femoral derotation osteotomy in children with cerebral palsy

Background: Femoral derotation osteotomy (FDO) is the standard treatment for internal rotation gait (IRG) in children with cerebral palsy (CP) although high rates of recurrence have been reported recently. Various factors associated with recurrence could be identified, but no predictor named. Research questions: Does FDO lead to a change of internal transversal hip moments? Are preoperative internal transversal hip moments a predictor for recurrence of IRG? Methods: 41 children with spastic bilateral CP and 72 limbs that received a FDO (10.4 +/- 2.7 years at surgery) were included retrospectively. Kinematic data were analyzed pre- (2 +/- 3 months), postoperatively (12 +/- 3 months) and at long-term follow-up (at least five years postoperatively; 84 +/- 13 months), internal transversal hip moments were analyzed pre- and postoperatively. Results: The maximum peaks of the internal hip rotation moment during loading response decreased significantly (p = 0.003). The minimum during the second half of the stance phase increased significantly (p = 0.004) and the initially internal externally rotating moment changed to an internal internally rotating moment. No correlation between changes in hip rotation from postoperatively to the long-term follow-up and the preoperative internal hip rotation moment could be identified. Significance: FDO leads to changes in internal hip rotation moments. Preoperative internal hip rotation moments can't be used as predicting factor for recurrence of IRG. The data suggest, that recurrence of IRG depends less on patient specific motion patterns, but more on the time point of surgery and the therapy of all concomitant deformities during SEMLS.