The long-term performance of a total of 712 Charnley and STH prostheses
was evaluated as a function of the patient's age (older than fifty years or
younger than fifty years) and of the underlying disease (osteoarthrosis,
rheumatoid arthritis, or avascular necrosis). In patients who were older
than fifty years, there were lower incidences of continuous cement-bone
radiolucency about the acetabular component (p = 0.04), wear of the
polyethylene acetabular cup (p = 0.03), and resorption of the calcar (p =
0.03). However, larger percentages of younger patients had rheumatoid
arthritis or avascular necrosis. In the cohort of patients who had
osteoarthrosis, the performance of the prosthesis did not differ
significantly between older and younger patients; therefore we attributed
the differences that were observed to the disease--that is, to rheumatoid
arthritis or avascular necrosis.