Mechanisms of stem subsidence in femoral impaction allografting

Failure of the femoral component of total hip arthroplasty is often accompanied by bone loss that can pose a significant challenge to the orthopaedic surgeon. Femoral impaction allografting has attractive potential for restoring bone stock in deficient femurs. However, there have been reports of problematic postoperative stem subsidence with this procedure. Subsidence is highly variable among patients, and there is disagreement over the mechanisms that cause it. This article reviews the various mechanisms that can contribute to subsidence in femoral impaction allografting. Variables such as graft density, cement penetration profile, use of synthetic graft substitutes, or other graft additives are discussed, as well as their potential impact on subsidence. Finally, recommendations are made for future studies aiming to reduce the risk of excessive subsidence in femoral impaction allografting.