Bone Alterations in Patients Undergoing Total Hip Arthroplasty

Bone alterations at the intertrochanteric bone-implant interface in patients undergoing total hip replacement (THR) can result in diminished bone fixation and increased femoral stem subsidence, with consequent implications for femoral component stability and the potential for short- and long-term aseptic loosening. This is of particular concern in young patients undergoing THR due to osteonecrosis of the femoral head (ONFH), a population in which inferior clinical outcomes compared with patients with primary osteoarthritis (OA) have been reported. Although factors frequently associated with ONFH, such as younger age and higher physical activity levels, may influence THR outcomes, studies using age-matched controls suggest that factors beyond patient demographics, including host bone quality, also contribute to clinical outcomes in this population. Age-stratified analyses performed by our group support this hypothesis. The pathological basis of trabecular bone alterations in patients with ONFH remains unclear. Micro-computed tomography imaging has shown that trabecular bone in the proximal femur of patients with ONFH exhibits an altered microstructure compared with that of patients with OA. Recently, the molecular mechanisms potentially involved in bone alterations in the proximal femur of these patients have been investigated through transcriptome analysis. In addition, in vitro cell cultures have provided insights into osteoblast behavior in contact with implant surfaces. Results from our group suggest that trabecular bone alterations in the intertrochanteric region of patients with ONFH may lead to greater femoral stem subsidence in cementless stems, which has been linked to aseptic loosening, instability, and leg length discrepancy. A better understanding of the extent of bone alterations in the proximal femur of patients with ONFH may help surgeons optimize surgical technique and femoral component selection to improve outcomes in this population.