Complications of femoral and acetabular modularity.

The versatility of modular total hip arthroplasties have rapidly extended their applications. However, these new interfaces can lead to complications that were not observed with monolithic components. These problems have been noted with modular femoral and acetabular components and have been associated with the generation of particulate debris. This article reviews the authors' clinical observations and histologic, biomechanic, and spectophotometric evaluations of modular total hip arthroplasties. New data comparing both synovial fluid metal levels in well-fixed and loose monolithic and modular prosthetic hip implants are presented. In modular total hip components, synovial fluid cobalt levels correlated positively with patient weight and length of implantation. The generation of particulate debris in modular total hip components may induce periprosthetic osteolysis. Taper locks for femoral components and locking mechanisms for the polyethylene liner and metallic cup must be designed to avoid the production of particulate debris.