Summary

Uncemented mobile-bearing UKA had superior long-term survivorship over the cemented fixation for the youngest patients (<60 years), with fewer revisions for OA progression and aseptic loosening.

Abstract

Introduction

An increasing number of patients are undergoing unicompartmental knee arthroplasty (UKA) at a younger age for isolated unicompartmental osteoarthritis (OA). Improved understanding of UKA survivorship by fixation type (cemented and cementless) across different age groups is required. This study aimed to investigate survivorship, reasons for revision and functional outcomes in patients undergoing cemented and uncemented mobile-bearing UKAs across different age groups in a large cohort study with long-term follow-up (up to 15-years)

Methods

A total of 1401 primary medial mobile-bearing UKAs from four large tertiary hospitals were included. The mean follow-up time was 7.2 ± 3.6 years (range 2-15.7 years). Clinical notes and radiographs were systematically reviewed to obtain patient and implant characteristics, revision-free survival and reasons for revision. Patients were stratified into three age bands: [1] <60 years; [2] 60-69 years; and [3] ≥70 years. Implant survivorship was analysed using Kaplan-Meier and reasons for revision and functional outcomes (Oxford Knee Score [OKS] at the 6-month, 5-year, and 10-year follow-up) were compared between groups by age bands and fixation type.

Results

Overall, there were 85 revisions with an overall implant survivorship rate of 93.9%. For the youngest age band (<60 years), 15-year survivorship was higher in the uncemented group compared to the cemented group (88.2% vs. 78.8%, p=0.02). There was no difference in 15-year survivorship for the 60-69 years and ≥70 years age bands by fixation type (91.7% vs. 80.6%, p=0.10; and 91.6% vs. 91.6%, p=0.55, respectively). For the cemented group, revision was most commonly performed for OA progression (41.7%) and aseptic loosening (33.3%), whereas for the uncemented group, revision was most commonly performed for bearing dislocation (50%). The rate of revision for bearing dislocation was higher in the uncemented group compared to the cemented group in both the <60 years and 60-69 years age bands, (50.0% vs. 0%, p=0.01; and 40.0% vs 0%, p=0.01). There were no differences in OKS between groups, except for higher OKS in the uncemented group, compared to the cemented group, for the 60-69 age band at 6 months (38.5 ± 8.1 vs 40.5 ± 7.2; p=0.03)

Discussion And Conclusion

Uncemented mobile-bearing UKA had superior long-term survivorship over the cemented fixation for the youngest patients (<60 years), with fewer revisions for OA progression and aseptic loosening. However, there was no difference in implant survivorship based on fixation type for older patients (≥ 60 years). Surgeons should consider uncemented fixation for UKA in younger patients (<60 years) who typically have higher levels of activity compared with older patients.