10-year survival rate of an all-polyethylene tibia medial unicompartmental knee replacement: the royal Berkshire hospital NHS foundation trust experience.

PURPOSE: This study aims to analyse the short- and long-term survival rate of an all-polyethylene tibia UKR, and the relationship with implant thickness and patient demographics including sex, age, ASA, and BMI.

METHODS

This was a single centre, retrospective, observational study of 388 consecutive medial fixed bearing all-polyethylene tibia UKRs done by a single surgeon between 2007 and 2019. We analysed the survival rate at 2, 5, 7, and 10 years and any relationship with sex, BMI, ASA, and implant thickness.

RESULTS

Cumulative implant survivorship was 98.7% at 2 years, 96.4% at 5 years, 95.3% at 7 years, and 91.9% at 10 years. The majority of patients had a BMI between 30 and 34 and were ASA 2; however, neither of these factors were associated with implant survival. The 7-mm all-polyethylene tibial component was most commonly used, and again, there was no association with implant size and survival. The most common reason for revision was progression of arthritis in the remaining compartments (40% of all revisions). There were no revisions due to loosening of the tibial component, and only 1.7% of revisions were due to femoral component loosening.

CONCLUSION

Fixed bearing medial all-polyethylene tibia UKR shows excellent survivorship at 2, 5, 7, and 10 years. There is no significant association with survivorship and sex, age, BMI, ASA grade, or implant thickness.