Study of the bone behavior around a neck preserving short stem implant: bone densitometric analysis over a span of two years

Purpose: Study the bone mineral density (BMD) changes and the remodelling process after implantation of a neck preserving short stem implant over a period of two years. Methods: Using specific patients’ selection criterion, a prospective study was done including 26 patients. All were operated upon by a single surgeon using the MiniHipTM, (Corin, Cirencester, UK). Mean age was 42.5 years. Clinical and radiological evaluation was done. Periprosthetic bone density was measured by DEXA. First scan was obtained within 10 days after surgery and served as a baseline for comparison. Results: The mean pre-operative Harris Hip score of 37.8 increased to 95.1 points two years post-operatively. BMD in the overall periprosthetic area showed a significant reduction during the first three months. Restoration to the original levels was reached in all zones except the most proximal zones at one year. A net increase was detected (+3%) after two years. Conclusion: The neck preserving MiniHip short stem implant has proven to be a bone-friendly design. Significant bone remodeling process continues after the first year. Although bone resorption in the greater trochanteric region is still a problem, however, it has proven that the BMD in all the other periprosthetic regions including the calcar and the lesser trochanteric regions, are subjected to bone formation process over a period of two years.