The generation of wear particles at the primary articulating interface of total hip arthroplasty is well documented. Particles may also be generated at the stem/cement interface in cemented prostheses. An investigation of explanted Capital femoral stems demonstrated that wear at the stem/cement interface had contributed to their early failure. This study compared the wear particle generated by stems of three different materials and with three different surface finishes. Three femoral stems were chosen as ‘templates’, one with a smooth surface,(the Exeter), one with a slightly roughened surface (the charnley) and one with a very rough surface (the capital). Their surfaces were measured and plates were manufactured with comparable surfaces in each of three materials in use for femoral stems, stainless steel, cobalt chrome and titanium alloy.

The plates were opposed to cement pins in a laboratory wear simulator. The volume of cement lost from the pins was measured and the debris generated was examined under the scanning electron microscope.

Analysis of the results demonstrated that for each of the materials tested, volume of wear particles generated increased as the roughness of the surface increased. When comparing similar surfaces in different materials it was also demonstrated that softer materials produced greater volumes of wear than harder materials.

The analysis of the debris demonstrated that material affected debris size; harder materials produced smaller cement particles than softer materials independent of surface finish.

Particles size and number of particles have been demonstrated to influence macrophage activity. The results of this study would suggest that softer materials should not be used for cemented stems with a rough surface finish.

We have examined 26 retrieved, failed titanium-alloy femoral stems. The clinical details, radiological appearances and the histology of the surrounding soft tissues in each patient were also investigated.

The stems were predominantly of the flanged design and had a characteristic pattern of wear. A review of the radiographs showed a series of changes, progressive with time. The first was lateral debonding with subsidence of the stem. This was followed by calcar resorption and fragmentation or fracture of the cement. Finally, osteolysis was seen, starting with a radiolucency at the cement-bone interface and progressing to endosteal cavitation.

Three histological appearances were noted: granulomatous, necrobiotic and necrotic. We suggest that an unknown factor, possibly related to the design of the stem, caused it to move early. After this, micromovement at the cement-stem interface led to the generation of particulate debris and fracture of the cement. A soft-tissue reaction to the debris resulted in osteolysis and failure of fixation of the prostheses.