Most computer navigation systems used in total hip arthroplasty integrate preoperative pelvic tilt to calculate the anterior
pelvic plane assuming tilt is constant; however, the consistency of pelvic tilt after THA has never been proven. Therefore,
using a modern comprehensive gait analysis before and after arthroplasty we sought to compare (1) dynamic pelvic tilt changes
and (2) pelvic flexion/extension range-of-motion changes. Twenty-one patients who underwent unilateral THA were prospectively
studied. Quantitative pelvic tilt changes (in the sagittal plane) and pelvic range of flexion/extension motion relative to
a laboratory coordinate system were compared using a computerized video motion system. Mean gait pelvic tilt was 13.9º ± 4.8º
(range, 1.73º–23.1º) preoperatively, 12.5º ± 4.5º (range, 1.4º–18.7º) 2 months postoperatively, and 10.5° ± 5.5º (range, –2.36º–19.2º)
12 months postoperatively. A significant proportion (31%) of patients had more than a 5° difference between preoperative and
12-month postoperative measurements and the variability was spread over 20°. Significant dynamic changes in pelvic tilt occurred
after THA. While navigation clearly improves the anatomical position of the component during THA, the functional position
of the component will not always be improved because of the significant change between preoperative and postoperative pelvic
tilt.
Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest,
patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
Each author certifies that his or her institution has approved the human protocol for this investigation and that all investigations
were conducted in conformity with ethical principles of research, and that informed consent for participation in the study
was obtained.