Aseptic loosening of straight- and curved-stem Müller femoral prostheses.

Out of 1099 Müller total hip prostheses with straight and curved stems consecutively implanted between 1980 and 1984, those performed in as homogeneous a group as possible of patients under the age of 70 years were selected for the present retrospective study. There were 158 straight femoral stems with cementless RM acetabular cups, 105 straight stems with cemented Müller acetabular cups, and 158 curved stems with cemented Müller acetabular cups, and their results over a mean follow-up period of 5.8 +/- 1.24 years were compared. Six (3.7%) curved and 5 (1.9%) straight-stem prostheses were exchanged due to aseptic loosening; 26 (16.3%) curved and 54 (20.1%) straight-stem prostheses were "at risk" or loose at the time of follow-up. Survival curves show a worse result for straight stems after 6 years; within a follow-up period of 6-8 years there was significantly more radiological loosening in straight stems than in curved. Loosening in straight stems is assumed to develop mainly as a physiological reaction to the presence of bone cement particles.