Densitometric evaluation of periprosthetic bone remodeling.

The application of Dual-energy X-ray absorptiometry (DEXA) in orthopaedic surgery gradually has been extended from the study of osteoporosis to different areas of interest like the study of the relation between bone and prosthetic implants. Aim of this review is to analyze changes that occur in periprosthetic bone after the implantation of a total hip arthroplasty (THA) or a total knee arthroplasty (TKA). In THA the pattern of adaptive bone remodeling with different cementless femoral stems varies and it appears to be strictly related to the design and more specifically to where the femoral stem is fixed on bone. Short stems with metaphyseal fixation allow the maintenance of a more physiologic load transfer to the proximal femur decreasing the entity of bone loss. Femoral bone loss after TKA seems to be related to the stress shielding induced by the implants while tibial bone remodeling seems to be related to postoperative changes in knee alignment (varus/valgus) and consequently in tibial load transfer. After both THA and TKA stress shielding seems to be an inevitable phenomenon that occurs mainly in the first year after surgery.