The effect of a thin coating of polymethylmethacrylate on the torsional fatigue strength of the cement-metal interface.

Recent studies have established that a mechanism of initiation of failure of fixation of cemented femoral components is debonding of the cement-metal interface. Other studies have shown that the torsional forces induced by stair climbing and rising from a chair are very high. Thus, the interface between the femoral prosthesis and the bone cement in total hip arthroplasty (THA) is required to transmit high torsional loads from the metal to the cement in a cyclic shear mode many times per year. These torsional loads likely contribute to the debonding. This study evaluated the efficacy of a thin layer of polymethylmethacrylate (PMMA) precoating in increasing the torsional fatigue strength of the cement-metal interface. Fatigue studies were performed on 15 specimens. Each specimen was tested with and without PMMA precoating. The PMMA precoat significantly and substantially increased the torsional fatigue strength of the cement-metal interface. Thus, PMMA precoating is likely to be a clinical advantage in maintaining the long-term integrity of the cement-prosthesis interface.