Establishing surgical indications for hamstring lengthening and femoral derotational osteotomy in ambulatory children with cerebral palsy by McCarthy, J, Shrader, MW, Graham, K, Veerkamp, M, Brower, L, Chambers, H, Davids, JR, Kay, RM, Narayanan, U, Novacheck, TF, Pierz, K, Rhodes, J, Rutz, E, Shilt, J, Shore, BJ, Theologis, T, Van Campenhout, A