Analysis of Long-Term Cemented Total Hip Arthroplasty Retrievals

A detailed biomechanical, histologic, and histomorphometric analysis of autopsy specimens from patients who previously had cemented total hip arthroplasty has helped to elucidate the skeletal response to cemented components. Bone cement has the capacity to provide long-term implant stability. The biologic response to polyethylene wear debris has a more critical effect on destabilization of cemented sockets compared with the femoral side. In contrast, mechanical events tended to predominate the early mode of destabilization of cemented femoral components with debonding at the metal-cement interface and fracture in the cement. Fractures predominate in cement mantles less than 1 mm thick and are associated with mantle defects, debonded interfaces, and sharp corners of the implants. Correlation of the histologic findings at the cement-bone interface with radiolucencies seen on clinical radiographs show that on the acetabular side radiolucencies represent a soft tissue membrane that is the biologic response to polyethylene debris. In contrast, on the femoral side, most radiolucencies were as a result of skeletal remodeling. Femoral adaptive bone remodeling is a diffuse process that occurs over the entire fixation surface. The most profound disuse osteoporosis occurred proximally in the proximal medial quadrant; however, when one takes into account all four quadrants, anterior, posterior, medial, and lateral, the most severe osteoporosis occurred at the midpoint of the stem.