EARLY PROSPECTIVE BONE MINERAL DENSITY CHANGES IN THE PROXIMAL FEMUR AFTER A FIELD HIP-CEMENTED FEMORAL COMPONENT-1 YEAR RESULTS

Aim: A prospective study was undertaken to define the pattern of bone remodelling using DXA following implantation of our polished, tri-tapered, collarless, cannulated cemented femoral component. Method: Our stem was implanted in 20 primary THRs. Our subjects comprised 7 male and 13 female patients. At the time of surgery the mean age was 73 (range 65 to 131). The mean weight at surgery was 75.4kg (range 47kg to 131.8kg) with a mean BMI of 28(range 22 to 40). All patients had a pre operative diagnosis of osteoarthritis. All the hips were implanted via the anterolateral approach. Pre-operative and sequential post-operative DXA evaluations were undertaken at 3 weeks, 6 and 12 months. Results: The mean precision error was 0.78%(range 0.8–3.4% depending on region of interest). Statistical analysis revealed a significant increase in BMD measured in zones 1,2,4,5,6 (p 0.05). The real percentage increase in BMD at 12 months was 43% in zone 1, 20% in zone 2, 8% in zone 3, 31% in zone 4, 12% in zone 5, 24% in zone 6 and 7% in zone 7. Conclusion: Peri-prosthetic bone remodelling has been observed within one year following total hip replacement (THR), which has been demonstrated by an increase in BMD in all zones. The implantation of our tri-tapered cannulated cemented femoral component, thus provides favourable proximal femoral loading at 12 months. Additional studies will determine whether stabilization of this bone turnover continues in the long term.