OUTCOME OF AN EXTENSIVELY HA-COATED STEM AT 18-YEAR FOLLOW-UP. A PROSPECTIVE STUDY OF 615 CASES.

Abstract

Bio-active fixation has increasingly gained acceptance over the last two decades. However extent of the coating is still a subject of debate. We introduced in 1986, the concept of total osteointegration of a tapered stem with the hope that we could achieve durable biological fixation while preserving a normal periprosthetic bone trophicity. Patients from our first clinical series using this stem are now eligible for 18-year follow up. Between July of 1986 and December of 1990 we performed 615 total hip arthroplasties using the Corail stem (DePuy). It is a straight tapered stem totally coated with a 150 μ thick layer of HA following an atmospheric plasma-spray process. The mean age at surgery was 64.5 (range 16 to 95 years) 242 patients are now deceased (39%), 62 (10%) patients are lost to follow-up. The mean follow-up for 243 living patients on file is 17.7years. 89 THAs required component revisions. 72 cup revisions were associated with wear and osteolysis. 8 cups and 4 stems have been revised for aseptic loosening. Owing to the high incidence of wear-related revision, Kaplan-Meïer survivorship at 18-year follow-up, using component revision for any reason as an endpoint, was 80.7±3.3 (95% confidence intervals). In contrast, Corail stem survivorship, using stem removal for any reason as an endpoint, was 95.0%±3.0 at 18-year follow-up, and considering aseptic loosening only, the survival probability of the stem is 98.9%±1.1 at 18 years. Therefore, despite wear and proximal osteolysis the fixation achieved with this totally HA-coated stem remained durable through 18-year follow-up. Regarding the periprosthetic remodelling during this period, modifications of the bone pattern have been strictly limited: slight resorption at the calcar level, absence of cortical hypertrophy, anecdotic significant stress-shielding. The radiological silence is one of the paramount facts demonstrated by this prospective study.