Long-term follow-up of bone remodelling after cementless hip arthroplasty using different stems.

The present paper is concerned with the investigation of the phenomenon of long-term bone remodelling on cementless hip replacements. Changes in bone density in the periprosthetic region around the stem, measured by dual X-ray absorptiometry (DXA), were used as a measure of the osseous adaptation reaction. A postoperative follow-up of the use of four different types of prostheses of varying design after on average 13.3 (11.4-14.5) years. Specifically, the prostheses assessed in this study were the CLS/Spotorno stem with the Allofit cup by Zimmer, the Vision 2000 stem with the Duraloc cup by DePuy Synthes, the AlphaFit stem with the AlphaLock cup by Corin and the Mayo stem with the Trilogy cup by Zimmer. For the DXA measurement, the femur was divided into the zones suggested by Gruen et al. On the femur, there was a significant reduction in bone mineral density (BMD) in the proximal Region Of Interest (ROI) 1 (p = 0.003) and 7 (p < 0.001), whilst there was a significant increase in ROI 4 (p = 0.03). A greater degree of bone atrophy was seen in patients aged 60 years and older and in female patients. A remarkable finding when comparing the stems was a significantly greater reduction in BMD in ROI 6 (p = 0.003) in the case of the Vision 2000 stem and a markedly, but not statistically significantly smaller reduction in BMD in ROI 7 (p = 0.18) in the case of the short-stem Mayo-type prosthesis. The best clinical results were found with the use of the latter. The investigations provide a starting point for establishing a differential indication in the choice of prosthesis types, depending on age and sex, the use of short-stem prostheses, as well as the administration of bone-effective drugs for the prevention of stress shielding.