Search

There have been several reports of osteolysis associated with rapid wear of Hylamer. A detailed analysis of retrieved implants and tissues can identify factors contributing to rapid wear and osteolysis. The mean linear wear rate of 12 liners was 0.49 mm/y, and 11 of 12 hips had progressive retroacetabular osteolysis. The average patient age was 50 years, and the mean implantation time was 50 months. All liners were sterilized by gamma irradiation in air. There was an 11-month difference in the average shelf-life of the 3 liners that were white and those that were darker in color. The volumetric wear rate of the white liners was 30% less than that of the others, suggesting a difference in the wear resistance of the liners as a function of shelf life. The mean average surface roughness (R a ) and the mean maximum surface roughness (R max ) of the femoral heads were increased 3-fold and 50-fold compared with typical values for unused femoral heads. Evidence of 3-body wear, such as metal particles embedded in the liners, was commonly present. The pattern of backside liner deformation and burnishing was consistent with relative motion between the liner and the shell. In addition to generating Hylamer wear particles, repetitive axial motion between the liner and shell could generate fluid pressure, which transmitted through holes in the acetabular shell could cause or contribute to the development of retroacetabular osteolysis. Hylamer particles of variable shape and size, consistent with generation by several wear modes, were isolated from periprosthetic tissues.

Infection, loosening, osteolysis, or other causes can lead to the development of pain about a previously well-functioning total hip arthroplasty. An inflammatory reaction unique to metal on metal arthroplasty can lead to a painful total hip. A synovial biopsy is needed to make this specific diagnosis, and included in the differential diagnosis is infection. The workup of infection includes obtaining a C-reactive protein and erythrocyte sedimentation rate. Elevations of both the C-reactive protein and erythrocyte sedimentation rate are felt to indicate possible infection. This case report describes both of these findings and the treatment rendered in a painful subluxing metal-on-metal total hip arthroplasty presenting with ongoing pain and a large effusion.

Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years.Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up were performed at three months postoperatively and yearly thereafter.The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of/=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005).The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary.Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.