Impact of femoral bone quality on stress transfer, remodeling, and failure risk in osseointegrated transfemoral prostheses

Osseointegrated transfemoral prostheses improve mobility but may induce stress shielding, periprosthetic bone loss, and long-term mechanical complications. Because amputees exhibit substantial variability in femoral geometry and cortical density, understanding how bone quality affects postoperative adaptation is essential. This study used three-dimensional finite element models coupled with a strain-energy-based remodeling algorithm to investigate how variations in femoral shaft diameter and initial apparent density influence stress transfer, density adaptation, and failure risk around the implant. Nine femur models were generated by combining three shaft diameters (24-28 mm) with three initial density levels. Remodeling was simulated over 60 months under physiological loading. Low-density femurs exhibited substantial proximal densification and pronounced distal bone loss, accompanied by elevated failure risk at the boneimplant interface. High-density femurs showed minimal remodeling and consistently lower stress and risk levels. Bone shaft diameter modulated, but did not override, the dominant effect of initial density. These findings highlight the importance of preoperative evaluation of cortical density and geometry when planning direct skeletal fixation in transfemoral amputees.