Aims
To compare the 10-year patient-reported outcomes, satisfaction and reoperation events following computer assisted kinematic alignment (KA) and mechanical alignment (MA) techniques in total knee replacement (TKR), using a randomised within-patient bilateral trial design to eliminate inter-patient variability.
Methods
Patients undergoing bilateral TKR were randomised to receive KA on one knee and MA on the contralateral knee. Previously published to you results revealed no differences in patient reported outcome measures but a patient preference for the KA aligned knee. Patient-reported outcome measures (PROMs) were collected at pre-operative baseline and at 1, 2, 5, and 10 years post-operatively. Outcomes assessed included the Forgotten Joint Score (FJS), KOOS-JR, Oxford Knee Score (OKS), and patient satisfaction measured on both a visual analogue scale (VAS) and a four-point Likert scale ("Would you have the operation again?"). Paired statistical comparisons were performed using Wilcoxon signed-rank tests or paired t-tests, selected on the basis of Shapiro-Wilk normality testing. Satisfaction Likert responses were additionally analysed as a binary outcome (Yes/No), with between-group comparisons using Fisher's exact test.
Results
A total of 41 paired observations available at ten years depending on the outcome measure. Pre-operative scores were well matched between groups for both KOOS-JR (KA 48.75 vs MA 49.27, p=0.783) and OKS (KA 22.90 vs MA 23.85, p=0.413). At ten years, there was no significant difference between KA and MA in any outcome measure. FJS was 82.59 (KA) versus 81.12 (MA) (p=0.401), KOOS-JR was 91.82 versus 89.89 (p=0.245), and OKS was 43.86 versus 43.48 (p=0.449). On binary Likert analysis, 100% of patients in both groups stated they would undergo the operation again at ten years, with no significant difference between groups (p=1.000). Outcomes at ten years were equivalent to those recorded at one and two years across all four PROMs, demonstrating that the functional gains achieved in the first year following surgery were maintained throughout the follow-up period. No significant between-group difference was identified at any time point for any outcome measure (all p>0.05). A single procedure was undertaken for a failed patellar component in a mechanically aligned knee at 10 years.
Conclusions
In this randomised within-patient bilateral trial, KA and MA produced equivalent patient-reported outcomes across all four PROMs and at all time points up to ten years. Both techniques achieved high and sustained functional scores and near-universal patient satisfaction and implants available at mid-long-term follow-up. KA is an effective alternative to MA without demonstrable superiority.
