86. DIGITALIZED MEASUREMENT OF FEMORAL BONE REMODELING AFTER TOTAL HIP ARTHROPLAST WITH A LOCKED STEM

Purpose of the study: Radiographs of 24 patients who underwent surgery for total hip arthroplasty (THA) with a locked stem were reviewed at 38 months mean follow-up using a dedicated software. This software enables digital analysis of standard radiographs with semiquantitative evaluation of bone density. Material and method: Good quality postoperative AP views of the femur and the same view at last follow-up were selected using the same criteria. These images were digitalised then analyses with the software. Bone density was established along a horizontal line 1 cm below the lesser trochanter perpendicular to the femur shaft. Computer analysis of bone density established three categories of patients as a function of cortical density: no cortical modification (n=5 hips), modification of only one cortical (n=11) and modification of both corticals (n=8). Results: Bone density increased, suggesting improve cortical bone stock as has been reported by most authors using the transfemoral approach and a non-cemented locked stem. Discussion: This result confirms the data in the literature; data which, unlike our series, were established on qualitative or subjective evaluations. The method presented here has the advantage of a semi-quantitative analysis, simple use, applicable to plain x-rays, and good reproducibility since all measures are made by the software. This study demonstrated the notion of cortical quality since it was not limited to a simple measurement of width, but also bone density, closer to real intraoperative observations. Conclusion: Use of this method enables longitudinal study to establish the kinetics of bone remodelling, compare results between surgical methods, and search for factors explaining observed variations.