Abstract
Aims: An argument against the use of canal-þlling, customized femoral stems has been that such implants have a large cross-sectional area and therefore are stiffer than standard, uncemented implants and thus induce more stress shielding and bone loss in the proximal femur. The purpose of this study was to evaluate the association between the volume of an uncemented, customized femoral stem and the postoperative changes in peri-prosthetic bone mineral density (BMD) measured with DEXA.
Material and methods: Forty-eight patients with a mean age of 46 years had a THR using a customized femoral stem (Unique, SCP, Norway). BMD was measured in the 7 Gruen zones postoperatively and after then 3, 6, 12 and 24 months. Based on the 3-D computer model of the implant the volume of the intrafemoral part of the stem was computed. The association between the relative change in BMD at the 2 years follow-up and the volume of the stem was assessed using Pearsonñs correlation test.
Results: A statistically signiþcant correlation between the volume of the intrafemoral part of the stem and change in BMD was found in Gruen zones 2, 4, 5 and for the overall BMD in all zones. No such correlation could be found for the most proximal zones (1, 6 and 7).
Conclusions: No consistent or strong association between the volume of the femoral stem and the periprosthetic stress shielding at 2 years postoperatively was found in this study. In particular, the bone remodelling in the most proximal part of the femur was not correlated to the size of the stem. Contrary to other studies, our þndings imply that stem size or stiffness is not a major determinant for proximal femoral stress shielding following total hip replacement.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
