The role of acetabular component screw holes and/or screws in the development of pelvic osteolysis.

Anecdotal reporting of osteolysis around cementless modular acetabular components with holes through the metal shell and/or iliac fixation screws has raised concern that such designs may generate excessive particulate debris and/or permit direct access of particulate debris to iliac bone. To address this issue, incidence data are reported on 513 total hip replacements from six different single-surgeon series of total hip arthroplasties performed with six different porous ingrowth acetabular components. With follow-up ranging from 40 to 108 months, a total of 45 pelvic osteolytic lesions were observed (8.8 per cent). Pelvic osteolysis was seen nearly as frequently in the ischium and pubis (21 lesions) as it was in the ilium (24 lesions). It was not possible to explain ischial and pubic osteolysis by holes and/or screws through the acetabular component shell. There was no direct correlation between the presence of screw holes or screws and the incidence of pelvic osteolysis. The incidence of pelvic osteolysis around modular components with holes through the shell was 4.5 per cent (14 of 313 hips). The incidence of pelvic osteolysis with solid-shell components was 15.5 per cent (31 of 200). The incidence of pelvic osteolysis around acetabular reconstructions with screws was 2.3 per cent (3 of 133). The incidence of pelvic osteolysis in reconstructions without screws was 11.1 per cent (32 of 380). The incidence of pelvic osteolysis in one-piece acetabular components (polyethylene pre-fixed in the metal shell) was 12.7 per cent (21 of 165) and the incidence of pelvic osteolysis with the modular components was 6.9 per cent (24 of 348). In each comparison, the incidence of pelvic osteolysis was actually lower in the group assumed to be at increased risk. Based on this review there does not appear to be a direct relationship between holes and/or screws through an acetabular component and the development of pelvic osteolysis. The incidence of pelvic osteolysis was associated with larger head diameters and longer follow-up. While screw holes may provide an access channel in specific cases, the present data indicate that the simple elimination of holes through the acetabular shell will not eliminate pelvic osteolysis. Regardless of other acetabular component design features, joint fluid and polyethylene wear particles from the femoral-acetabular articulation can gain access to bone behind an acetabular component via the peripheral implant-bone interface through regions without sufficient contact or tissue ingrowth. The development of pelvic osteolysis is multifactorial and includes the total volumetric wear of polyethylene as well as specific features of the acetabular component design and reconstruction technique.