Short stem prostheses have been developed to preserve proximal femoral bone stock. This prospective, randomized study compared periprosthetic bone remodelling following short and straight stem implantation 1 year after surgery.
One hundred and forty-four consecutive patients undergoing total hip arthroplasty were randomized to either a Fitmore short or a cementless straight stem (both Zimmer, Winterthur, Switzerland). Periprosthetic bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry performed the day before surgery and at 7 days, 3 months and 1 year postoperatively. Furthermore, the HHS and the WOMAC were obtained.
One hundred and thirty-eight patients completed 1-year follow-up. Periprosthetic BMD changes at 1 year were most pronounced in the proximal medial region of interest (ROI) 7 with -17.2% after short stem and -16.7% after straight implantation (p = 0.67). However, there was significantly less BMD reduction in ROI 6 following short (-4.7%) versus straight stem (-10.8%) implantation (p = 0.01). There were no significant differences between the two groups in terms of the HHS and the WOMAC either before or after surgery.
One year after surgery, both stems showed an implant-specific periprosthetic bone remodelling. Nevertheless, proximal load transfer was more pronounced after short stem implantation than with a straight stem.