Early experience with eccentric acetabular components in revision total hip arthroplasty.

Osteolysis associated with acetabular component loosening can produce significant acetabular defects. The combined (segmental and cavitary) or type III defect can present a very challenging reconstructive problem. Several methods of reconstruction for type III defects have been described, including the use of oblong or eccentric sockets. These implants are attractive, theoretically, because they allow restoration of the hip center without use of structural bone graft. The results of this method however have not been widely reported. From a series of type III defects reconstructed from 1987 to 1991, six hips were reconstructed with eccentric acetabular components, provided by three different manufacturers. Four of these six implants were custom and two were off-the-shelf. At 4-years minimum follow-up, three of the six sockets had failed and had been revised. All three failures had been custom implants produced by the same manufacturer. The other three sockets had produced good clinical results. The features common to the failed implants were: (1) custom manufacture; (2) small ingrowth pads not integral with the body of the implant; and (3) lack of specific instrumentation (reamers) for insertion of the implant. Eccentric sockets may have limited, although well-defined, indications for use, such as acetabular revision needed in the presence of a well-fixed or monolithic femoral stem. Early experience suggests that custom eccentric acetabular components are not well suited for such indications.