The John N. Insall Award: Functional versus Mechanical Alignment in Total Knee Arthroplasty: A Randomized Controlled Trial
Abstract
INTRODUCTION
Mechanically aligned (MA) total knee arthroplasty (TKA) is regarded as a gold standard; however, some patients report dissatisfaction post-surgery. Functional alignment (FA) is a potential alternative, integrating kinematic alignment (KA) principles with pre-resection bone balancing within defined boundaries. The use of FA aims to improve outcomes by restoring native joint lines and optimizing soft-tissue balance. However, comparative evidence is limited.
METHODS
This prospective, randomized controlled trial compared MA (n = 121) and FA (n = 123) in robotic-assisted TKA. For MA, components were positioned perpendicular to the limb mechanical axis, with soft-tissue releases to achieve balance. For FA, initial virtual component positioning was used to match native knee anatomy (KA), with adjustments for soft-tissue balance before bone cuts. The primary outcome was the forgotten joint score (FJS). Outcomes were compared with a mixed-model analysis of variance.
RESULTS
At the two-year follow-up, the mean FJS was comparable (MA: 64.4 ± 30.1 versus FA: 70.1 ± 25.6, P = 0.10). The MA cases had more soft-tissue releases than FA (65 versus 16%, P < 0.001). Compared to MA patients, FA patients had higher Knee Injury and Osteoarthritis Outcome (KOOS) Symptoms (86.6 ± 12.9 versus 82.5 ± 14.0, P = 0.01) and KOOS-Quality of Life (QOL) scores (76.1 ± 20.3 versus 70.7 ± 22.7, P = 0.03). More FA patients 'would recommend' the procedure (94 versus 82%, P < 0.01). For patients who…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 123 participants or records.
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