Activity relationships of total hip arthroplasty in patients with osteonecrosis and osteoarthritis.

We compared the age adjusted results of all primary Osteonics total hip arthroplasties with osteonecrosis and osteoarthritis. The Harris index hip score was used for the analysis. Twenty-eight patients had osteoarthritis and 26 patients had osteonecrosis. The Harris hip score was used to compare the osteoarthritis and osteonecrosis gross. Patients with osteoarthritis gradually increased in Harris hip score, whereas osteonecrosis patients gradually decreased in Harris hip score over 60 months. However, after the patients were adjusted for age above and below 50 years, the trend for each group was similar despite the diagnosis. All patients below 50 years of age, regardless of diagnosis, gradually decreased in hip score over time. On the other hand, all patients over 50 had a gradual increase in hip score with time. The poor results seen in patients with osteonecrosis may be related more to age and activity level than to the primary diagnosis. We do not believe that the diagnosis of osteonecrosis plays as significant a role in the final outcome of a total hip arthroplasty as does the patient's age and, more importantly, activity level following hip arthroplasty.