Long-term outcomes of external femoral derotation osteotomies in children with cerebral palsy

External femoral derotation osteotomy (FDO) is an orthopaedic intervention to correct increased femoral anteversion and associated excessive internal hip rotation and internal foot progression during gait in children with cerebral palsy. The resulting functional issues may include clearance problems and hip abductor lever-arm dysfunction. The purpose of this study was to evaluate long-term gait outcomes of FDO. Twenty ambulatory patients (27 sides) with cerebral palsy who underwent pre-operative (P0) and a one year post-operative (P1) gait analysis as part of the standard of care had a second post-operative analysis (P2) approximately 11 years post-surgical intervention. Mean hip rotation in stance showed statistically significant decreases in internal rotation at P1 post-surgical intervention that were maintained long-term (mean hip rotation P0: 21 ± 9, P1: 0 ± 9 and P2: 6 ± 12  degrees internal). Similar results were seen with mean foot progression (P0: 9 ± 16 degrees internal, P1: 14 ± 13 degrees external, P2: 13 ± 16 degrees external). However, 2/27 sides (9%) showed a recurrence of internal hip rotation of >15° at the 11 year follow-up. The reasons for this recurrence could include age, surgical location and ongoing disease process all of which need to be further examined. We conclude that FDO can show long-term kinematic and functional benefits when performed in the prepubescent child with cerebral palsy in comparison to the natural progression of of hip rotation in cerebral palsy.