MAINTENANCE OF PROXIMAL BONE MASS WITH AN UNCEMENTED FEMORAL STEM ANALYSIS WITH DUAL-ENERGY X-RAY ABSORPTIOMETRY

Bone ingrowth into uncemented femoral implants with proximal porous co atings has been designed to avoid proximal stress shielding and preser ve femoral strength. Dual-energy x-ray absorptiometry allows repeated quantitative analysis of anteroposterior scans of the proximal femur. By use of dual-energy x-ray absorptiometry and qualitative radiographi c changes, 31 total hip arthroplasties with an individually designed, proximally porous-coated prosthesis were evaluated after surgery and a t intervals up to 2 years. All implants appeared to achieve successful bone ingrowth and subsequent remodeling. At the most proximal level a round the neck osteotomy, the postoperative loss of bone density al 6 months was -14.5%, which persisted at 24 months with -11.6%. At the le vel of the distal portion of the porous coating in the lower metaphysi s, the density change was -8.7%, but bone had remodeled at 24 months w ith a change in density of only -1.0% compared with the immediate post operative scan. With a design that results in reliable proximal ingrow th, this study predicts that after an initial decline in bone density, a positive bone remodeling response occurs that could lead to long-te rm stable fixation of the femoral implant.