[A comparison of all-polyethylene and metal-backed tibial components in total knee arthroplasty].

PURPOSE OF THE STUDY: The purpose of our study was to compare the clinical, functional and radiological results of two types of tibial components for the same total knee prosthesis (posterior stabilized HLS), all-polyethylene (group A) and metal-backed (group B), in order to answer the following question: does use of an all-polyethylene piece affect mid-term outcome of total knee arthroplasty (TKA)?

MATERIAL AND METHODS: This was a retrospective comparative analysis of a single-center non-randomized consecutive series of 169 patients with an all-polyethylene posterior stabilized cemented gliding TKA. This series was matched with another retrospective series of 169 posterior stabilized cemented TKA with a metal-backed tibial piece. Matching factors were age, gender, etiology, and follow-up. The two series were extracted from our database which included all patients who underwent surgery for a TKA in the same institution (Lyon Civil Hospices) performed by one of the authors (PN) or under his responsibility between 1987 and 1996 for group A (all-poly) and between 1987 and 1997 for group B (metal-backed). Mean follow-up was 66 months. The IKS scores and radiological findings were recorded.

RESULTS: In group A, 96% of patients were satisfied, 93% in group B. The IKS knee score for group A was 89 +/- 10.8 and 88.3 +/- 11.9 for group B. The function score was 68 +/- 23.7 in group A and 71 +/- 24 in group B. Mean flexion was 113 degrees for both groups. Non-progressive lucent lines were noted in 27 cases in group A and 23 in group B. Revision TKA was performed for 18 knees in group A, including six with implant replacement (three of them for infection). In group B, there were ten revisions, seven with implant replacement including one with infection and three without implant replacement. The 10-year survival was 94.5% in group A and 93.64% in group B. There was no significant difference in the function and knee scores, the presence of lucent lines, and the number of implant replacements between group A and group B (p>0.05).

DISCUSSION: This study was unable to demonstrate any superiority in clinical and radiological results for TKA between the all-polyethylene and metal-backed options at five years follow-up.