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Knee

INVESTIGATING PRIMARY AND LONG-TERM FIXATION OF THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY TIBIAL COMPONENT: TEN-YEAR RESULTS OF A RANDOMIZED CONTROLLED TRIAL COMPARING CEMENTED AND CEMENTLESS FIXATION USING RADIOSTEREOMETRIC ANALYSIS

The British Association for Surgery of the Knee (BASK) May 2022 Meeting, Newport, Wales, 17–18 May 2022.



Abstract

Abstract

Introduction

Cementless fixation of Oxford Unicompartmental Knee Replacements (UKRs) is an alternative to cemented fixation, however, it is unknown whether cementless fixation is as good long-term. This study aimed to compare primary and long-term fixation of cemented and cementless Oxford UKRs using radiostereometric analysis (RSA).

Methodology

Twenty-nine patients were randomised to receive cemented or cementless Oxford UKRs and followed for ten years. Differences in primary fixation and long-term fixation of the tibial components (inferred from 0/3/6-month and 6-month/1-year/2-year/5-year/10-year migration, respectively) were analysed using RSA and radiolucencies were assessed on radiographs. Migration rates were determined by linear regression and clinical outcomes measured using the Oxford Knee Score (OKS).

Results

Preliminary analysis of Maximum Total Point Motion (MTPM) indicated cementless tibial components undergo significantly more migration than cemented components during the first 6 months (1.6mm/year, SD=0.92 versus 1.3mm/year, SD=1.1, p<0.001). Cementless migration was predominantly subsidence inferiorly (Mean=0.51mm/year, SD=0.29, p<0.001) and posteriorly (0.13mm/year, SD=0.21, p=0.03). Contrastingly, from 6 months to 10 years cemented components migrated significantly (MTPM=0.039mm/year, SD=0.11, p=0.04) whereas cementless components did not (MTPM=0.002mm/year, SD=0.02, p=0.744). Radiolucent lines occurred more frequently below cemented (10/13) than cementless (4/16) tibial components, but radiolucencies did not correlate with differences in migration or OKS. There was no significant difference in OKS between cemented and cementless.

Conclusion

These results suggest that cementless tibial components migrate more than cemented before achieving primary fixation. However, long-term fixation of cementless tibial components appears to be as good, if not better, than cemented with the benefit of fewer radiolucent lines.