The purpose of this study was to examine changes in pelvic inclination and spino-pelvic alignment about the pelvic tilt in individuals with severe posterior pelvic inclination after total hip arthroplasty. We treated six patients with severe posterior pelvic inclination (6 males, mean age 75 years), to create a pelvic inclination of 35 degrees in the upright position.
We evaluated the pelvic inclination angle (PIA), anterior pelvic plane (APP), length from the C7 plumb line to the hip axis (C7-HA), and compared the preoperative state with that at one year postoperatively.
Postoperatively, we classified the patients into two groups : three with posterior pelvic inclination, and three with anterior pelvic inclination.
Changes in each of the parameters (posterior pelvic inclination groups/anterior pelvic inclination groups) included PIA in the decubitus position 8.2°/1.3°, PIA in the upright position 4.0°/-6.2°, APP-0.4°/8.0°, and C7-HA-18.8mm/-40.1mm.
In the posterior pelvic inclination groups, lumbar lordosis decreased and C7-HA moved backwards. In the other groups, C7-HA moved forward.
We expected that posterior pelvic inclination would become more severe after THA. However, posterior pelvic inclination did not change in half of the patients. Thus we found that postoperative pelvic inclination does not change greatly.
