Failure of Three Cementless Modular Total Hip Arthroplasty Prostheses: A Retrieval Analysis

The reasons leading to the in vivo failure of three titanium alloy modular implants in cementless total hip arthroplasty were investigated. The implantation period ranged from 18 months to over three years. Two were fractured in vivo and the other was retrieved secondary to aseptic loosening after 18 months in service. Macroscopic examination showed close topographical similarities between the two fractured implants. Dark elliptical striations on the fractured site indicated the occurrence of low cycle fatigue. Light Microscopy and Scanning Electron Microscopy confirmed the presence of fretting, pitting, plastic deformation, and stress-induced corrosion cracking. In two of the three implants, EDS confirmed metal ion traces in the tissue around the implant. However, nothing unusual was found in the third unfractured implant. Taper performance is influenced by metallurgy, the load carried and the effect of the local microenvironment. Methods to reduce the impact of these factors may reduce the incidence of taper related failure.