The elevated-rim acetabular liner in total hip arthroplasty: relationship to postoperative dislocation

Abstract

Although an acetabular component with an elevated rim is thought to improve the postoperative stability of a total hip prosthesis, the actual clinical value has not yet been demonstrated. To address this question, we reviewed the results of 5167 total hip arthroplasties that had been performed at our institution from April 1, 1985, through December 31, 1991. The prostheses included 2469 acetabular components with an elevated-rim liner (10 degrees of elevation) and 2698 with a standard liner. The cumulative probability of dislocation was estimated as a function of time since the operation with use of the Kaplan-Meier survivorship method. Forty-eight of the 2469 hips that had the elevated-rim acetabular liner dislocated within two years, compared with 101 of the 2698 hips that had the standard acetabular liner. The two-year probability of dislocation was 2.19 per cent for the hips with the elevated-rim liner and 3.85 per cent for those with the standard liner (p = 0.001). A similar trend was seen at five years; however, because of a smaller sample the difference was not significant. Increased stability at two years was also demonstrated for the hips with the elevated-rim liner when the hips were analyzed according to the operative approach, the mode of fixation, the sex of the patient, and the type of total hip arthroplasty (primary or revision). Although these data demonstrate improved stability after total hip arthroplasty when an elevated liner is used, particularly in hips that are at greater risk for dislocation of the prosthesis, the long-term effect of this elevated liner on wear and loosening remains unknown but is of considerable concern. The elevated liner deserves additional study to clarify its effect on wear and loosening.