Kinematic pelvic tilt during gait alters functional cup position in total hip arthroplasty

Static pelvic tilt impacts functional cup position in total hip arthroplasty (THA). In the current study we investigated the effect of kinematic pelvic changes on cup position. In the course of a prospective controlled trial postoperative 3D-computed tomography (CT) and gait analysis before and 6 and 12 months after THA were obtained in 60 patients. Kinematic pelvic motion during gait was measured using Anybody Modeling System. By fusion with 3D-CT, the impact of kinematic pelvic tilt alterations on cup anteversion and inclination was calculated. Furthermore, risk factors correlating with high pelvic mobility were evaluated. During gait a high pelvic range of motion up to 15.6 degrees exceeding 5 degrees in 61.7% (37/60) of patients before THA was found. After surgery, the pelvis tilted posteriorly by a mean of 4.0 +/- 6.6 degrees (p < .001). The pelvic anteflexion led to a mean decrease of -1.9 +/- 2.2 degrees (p < .001) for cup inclination and -15.1 +/- 6.1 degrees (p < .001) for anteversion in relation to the anterior pelvic plane (APP). Kinematic pelvic changes resulted in a further change up to 2.3 degrees for inclination and up to 12.3 degrees for anteversion. In relation to the preoperative situation differences in postoperative cup position ranged from -4.4 to 4.6 degrees for inclination and from -7.8 to 17.9 degrees for anteversion, respectively. Female sex (p < .001) and normal body weight (p < .001) correlated with high alterations in pelvic tilt. Kinematic pelvic changes highly impact cup anteversion in THA. Surgeons using the APP as reference should aim for a higher anteversion of about 15 degrees due to the functional anteflexion of the pelvis during gait.

Automated summary

The study found that kinematic pelvic changes have a significant impact on cup anteversion in total hip arthroplasty (THA). After surgery, the pelvis tilted posteriorly by an average of 4.0 degrees, leading to changes in cup inclination and anteversion. Factors such as gender and body weight are correlated with high alterations in pelvic tilt.