Little is known about the survival of total hip arthroplasty implants with bioactive coatings beyond the first 20 years. The authors aimed to report survival of a tapered hip stem fully coated with hydroxylapatite (HA) at follow-up of 25-30 years.
Of the original series of 320 patients (347 hips), 12 patients (12 hips) had stem and cup revisions, 54 patients (55 hips) had cup revisions, 17 patients (17 hips) had liner exchange. A total of 207 patients (225 hips) died with stems in place and 21 patients (24 hips) could not be reached. This left a cohort of 80 patients (86 hips) with their original stem for assessment. Survival was analyzed using the Kaplan-Meier (KM) method and cumulative incidence function (CIF).
Considering stem revision as endpoint, the revision risk calculated using the KM method was 6.3%, whereas using the CIF it was 3.7%. Considering any reoperation as endpoint, the revision risk calculated using the KM method was 41.2%, whereas using the CIF it was 25.9%. The Harris Hip Score for 77 patients (18 hips) was 81.6 ± 15.2. Standard x-rays were available for 52 hips (49 patients), and 10 (19.2%) showed radiolucencies <2 mm thick.
This study is the first to report outcomes of an HA-coated stem beyond 25 years. The survival of stem compares favorably with long-term survival of the Charnley cemented stem, and with shorter-term registry studies. The stem achieved its intended purpose of total osteointegration in the long-term, although the proximolateral region remains susceptible to radiolucencies.