Heterotopic ossification after direct lateral approach and transtrochanteric approach to the hip.

The incidence of heterotopic ossification after total hip replacement using the direct lateral approach is compared to the incidence using the transtrochanteric approach. All the initial ectopic ossification occurred by six months following the implant with noncemented fixation. The direct lateral approach adds slightly to the incidence of ectopic ossification as compared to the transtrochanteric approach. Heterotopic ossification of minimal grade did not interfere with any of the planar motions of the hip, whereas severe ectopic ossification disabled the hip in several planes of motion and restricted it significantly in the others. The more severe form of ectopic bone was more common after the transtrochanteric approach to the hip, while the lighter form developed more often following the direct lateral approach.