UNPOLISHED VERSUS POLISHED CEMENTED FEMORAL PIECES: RESULTS AT MINIMUM TEN YEARS

Abstract

Purpose: Certain authors have indicated that the primum movens of loosening of cemented femoral stems is related to the decohesion of the cement implant interface. Under such conditions, improvement in this interface was attempted with the development of a rough surface for the femoral piece. The purpose of this retrospective analysis was to evaluate results a minimum ten years follow-up in a consecutive series of total hip arthroplasties comparing types of femoral implant surfaces.

Material and methods: Between January 1988 and December 1989, 311 THA were implanted in 286 patients aged 63.6±11.8 years (26–91). All implantations were performed via the transtrochanteric approach by two senior surgeons. Two types of femoral implant were used: 166 non-polished pieces with a round section Ra = 3 mm (CMK3, Vector Orthopédique) and 145 polished pieces with a quadrangular section Ra = 0.4 mm (MKIII, Stryker Howmedica). The preoperative data were comparable for the two groups. Functional results were assessed with the Postel Merle d’Aubigné score (PMA). Actuarial survival curves were plotted.

Results: At minimum ten years follow-up, 187 patients (204 hips) were living and had not required revision at mean follow-up of 11.7±2.5 years (10–14), 15 patients (15 hips) had revision of the acetabular and/or femoral element, 54 patients (58 hips) had died, and 30 patients (34 hips) were lost to follow-up. The mean preoperative function score was 11.2±2.5 (4–16) versus 17.5±0.5 (10–18) at last follow-up (Wilcoxon rank test, p< 0.001). Cumulative survival at 13 years, taking radiographic loosening of the femoral piece as the endpoint, was 78.9±5.8% (95%CI 67.6–90.3%) for unpolished implants versus 97.3±2.6 (95%CI 92.2–100) for polished implants. The difference was significantly different (p< 0.001).

Discussion: The results of this analysis indicate that radiographic survival of unpolished cemented femoral pieces is significant inferior compared with polished pieces. The increased adherence of the femoral cement is probably the cause of increased shear stress at the bone-cement interface. The respective influence of section and surface remain to be determined.