Summary

Patients who progress to a staged bilateral knee arthroplasty can expect outcomes that are similar to or exceed those of the unilateral TKA

Abstract

Introduction

Recent estimates suggest that up to 40% of patients with total knee arthroplasty (TKA) will require a subsequent TKA in the contralateral knee within 10 years. The success of TKA in improving the pain and function associated with knee osteoarthritis has been well-established. However, most research has focused on assessing outcomes from a single TKA procedure and it is unclear whether patients who progress to bilateral TKA can expect a return to function that is comparable to their outcome following the initial unilateral surgery. The aim of this study was to compare the pre-operative functional limitations between the first (unilateral) and second (progression to bilateral) TKA procedures, and to compare the post-operative functional outcomes between the first and second TKA procedures. A secondary aim was to compare the eventual outcomes of these patients with bilateral TKA to a control cohort of patients with unilateral TKA.

Methods

All consecutive unilateral TKA patients of a single experienced knee surgeon were recruited for this study. Patients who progressed from an initial unilateral TKA to bilateral TKA formed the participant group that is the focus of this study. Patients who did not progress to bilateral TKA formed a control cohort for comparison. Patients were assessed immediately prior to, and 12 months following each surgery using the Knee Society Knee Score and the Oxford 12 Knee Score. At the post-operative assessment, comfortable walking speed was also assessed using a six metre walking test. Within-participant comparisons were completed for each outcome using a paired t-test and between-group comparisons were completed using an independent t-test.

Results

Data from 101 participants who progress from unilateral to bilateral TKA were included in this analysis. On average, participants were 65.7 (SD=7.1) years of age at the time of the unilateral TKA and 60.4% were female. The mean time between the unilateral TKA and progression to bilateral TKA was 2 years and 12 days.
As expected, all outcomes significantly improved following the first and second TKA surgeries (p<0.01 for all comparisons). However, there were differences in both the pre-operative and post-operative assessments between each surgery. Immediately prior to the second TKA, patients had higher Knee Society Score (p=0.008) but scored more poorly on the self-reported Oxford 12 measure of function (p<0.01) than prior to the first TKA. Following the second TKA, patients had higher Knee Society Scores (p=0.021) and walked faster (p=0.002) than following the first TKA.
Post-operative outcomes for these patients who progressed to bilateral TKA were not different to patients with unilateral TKA.

Discussion

Patients who progress from unilateral to bilateral TKA can expect outcomes following the second surgery that are similar to or exceed those of the first (unilateral) TKA. Differences between the pre-operative assessments of the first and second surgeries suggest that following an initial TKA, patients may be less tolerant of limitations in function and more willing to seek surgical intervention than prior to the first surgery. Outcomes for patients who progress to bilateral TKA are not inferior to those of patients with unilateral TKA.