抄録
Objectives: The purpose of this study was to investigate changes in pelvic inclination angle (PIA) between the supine position and standing position after total hip arthroplasty (THA), and the correlation between cup position and PIA. Furthermore, we also examined the effects of pelvic tilt on ultra-high molecular weight polyethylene (UHMWPE) liner wear.
Methods: Fifty-three patients who underwent primary cementless THA (68 hips) were included in this study. In all cases, the porous-coated anatomic total hip system (Stryker Howmedica Osteonics, Allendale, NJ) with a conventional UHMWPE liner and a 26-mm cobalt-chromium femoral head were used. We measured PIA, cup inclination and anteversion angle in the supine and standing positions at the final follow-up. Annual polyethylene liner wear rate in the supine position was also measured. We performed multiple regression analysis between the annual polyethylene liner wear rate and the following factors in both positions including age at surgery, gender, PIA, cup inclination and anteversion.
Results: The mean annual polyethylene liner wear rate was 0.24 mm/year. PIA was 24.7° in the supine position, and 31.6° in the standing position (p < 0.01). Cup inclination was 40.2° in the supine position and 41.9° in the standing position (p < 0.01), while cup anteversion was 14.5° in the supine position and 18.2° in the standing position (p < 0.01). Multiple regression analysis revealed that the annual polyethylene linear wear rate was found to increase significantly with increase of cup inclination and PIA in the supine and standing positions. Adjusted R2 was 0.09 in supine position and 0.16 in standing position, respectively.
Conclusion: This study has shown that cup inclination and PIA affect the polyethylene wear rate. A comparison of adjusted R2 for the supine position and the standing position revealed that cup inclination and PIA in the standing position have a greater influence on polyethylene wear.
