Bone Remodelling in THA: A Comparative DXA Scan Study between Conventional Implants and a New Stemless Femoral Component. A Preliminary Report

Periprosthetic bone loss is a major cause for concern in patients undergoing total hip arthroplasty (THA). There are many different factors that may determine the pattern of bone loss and bone remodelling following THA, such as the quality of the bone before the hip replacement, skeletal bone mass at the time of the operation, material and method of fixation and implant design. Recent developments in dual-energy X-ray absorptiometry (DXA) have made it possible to quantify bone mineral density (BMD) to evaluate changes around the prosthesis and to measure bone stock and bone density redistribution after a total hip replacement. In this cross-sectional multicentre clinical study the DXA method was used to compare bone mass after uncemented THA of a custom-made stemless design with five groups of conventional cementless implants (Alloclassic, Mayo, CFP, IPS, ABG). The adaptive bone changes of the proximal femur three years after implantation were evaluated. Periprosthetic BMD was measured in 130 subjects in the seven regions of interest (ROI) based on Gruen zones. Significant differences were found between the stemless implant and the other five groups in zones 1, 4 and 7. The CFP, IPS, and ABG groups showed decreased BMD in ROI 1, and the Mayo, IPS and Alloclassic in ROI 7. An increased BMD in ROI 4 was observed in the Mayo, IPS, ABG and Alloclassic groups. The results of the present study suggest that a conservative stemless implant with complete proximal load transfer produces a homogeneous and more physiological redistribution of bone density, allowing maintenance of proximal periprosthetic bone stock.