CEMENTED ALL-POLYETHYLENE CUPS VERSUS UNCEMENTED POROUS COATED CUPS – 10 YEAR RESULTS OF PROSPECTIVE RANDOMISED STUDY.

Abstract

Background: Cemented and cementless fixations of acetabular components in total hip arthroplasty are routine practice with inherent advantages and disadvantages. The aim of our prospective randomized study was to compare the clinical and radiographic results of cementless porous-coated cobalt chromium acetabular component with cemented all-polyethylene acetabular component in total hip arthroplasty.

Methods: Three hundred patients were randomized to receive a cementless hemispherical cobalt chromium porous-coated no-hole acetabular component (group 1) or cemented all-polyethylene acetabular component (group 2) with an identical cemented femoral stem and 28mm cobalt-chromium head. Patients were evaluated clinically with Harris Hip Scores (HHS) and radiographically. Analysis of both intention-to-treat groups was performed.

Results: Group 1 had 128 patients (55 male, 73 female) with average age of 70.3 years. Group 2 had 147 patients (63 male, 84 female) with average age of 71.2 years. Average follow-up was 9.5 years (1.03–13.23). The median follow-up was 10 years. 25 patients were excluded from analysis for reasons including unfit for surgery (2), operation cancelled (2), missing data (8) and non-study device (10). Average preoperative HHS improved from 34.4 and 34.5 to 80 and 82.5 postoperatively in group 1 and 2 respectively. There was no statistically significant difference between the average HHS of the two groups (p=0.449) at last follow-up. There were 7 revisions in group 1 [infection (2), cup migration (2), aseptic loosening (1), slipped cup (1) and fractured liner (1)]. 11 patients had revision in group 2 [aseptic loosening (8) and recurrent dislocations (3)]. Revision rate between the two groups was not statistically significant (p=0.465). 10-year survivorship was 93.8%; and 86.6%; for group 1 and 2 respectively. No statistically significant difference was noted for prognostic factors like gender (p=0.006), body mass index (p=0.433), age (p=0.657) and surgical approach (p=0.004) for the two groups. Prognostic factors like gender (male, p=0.006) and surgical approach (posterior, p=0.004) were noted to be significant but body mass index (p=0.433) and age (p=0.657) had no statistical significance. Bootstrapping analysis for the two groups (p-value calculations N=3000) showed a significant p-value for 19 and not significant p-value for 2981 calculations. 4 porous coated cups and 29 all-polyethylene cups had radiolucencies. None of the porous-coated cups had expansile osteolysis.

Conclusions: The results from our study indicate that patients with a cemented all-polyethylene cup and cementless porous coated cup have similar long term outcomes. In patients over 75 years cemented cups have excellent results (100% survivorship at 10 years).