No differences in functional and clinical outcomes after rehabilitation between modified kinematic and mechanical alignment in total knee arthroplasty: A randomized controlled trial.

Abstract

Purpose: Despite advancements in total knee arthroplasty (TKA), patient dissatisfaction remains notably high (15%-25%). This dissatisfaction will be multifactorial, one of which may be the alignment of the components. Kinematic alignment (KA), aimed at restoring pre-arthritic knee anatomy, is proposed as a promising alternative to mechanical alignment (MA), potentially offering better functional outcomes and improved gait characteristics.

Methods: A randomized controlled trial was conducted involving 100 patients undergoing primary TKA. Patients were randomized into two groups (KA vs. MA) using a navigation-assisted surgical approach, with follow-ups conducted at 1 year post-operatively. Outcomes assessed included patient-reported outcome measures (Knee Society Score, Western Ontario and McMaster Universities Osteoarthritis Index, Visual Analogue Scale and Forgotten Joint Score), radiological alignment and comprehensive gait analysis (kinematics, kinetics and spatio-temporal parameters).

Results: Navigation analyses indicated significant post-operative alignment differences, with KA showing significantly more varus tibial (KA: 2.2 ± 2.8° vs. MA: 0.3 ± 0.6°, p < 0.001) and more valgus femoral cuts (KA: -0.7 ± 2.9° vs. MA: 0.3 ± 0.8°, p = 0.02) compared to MA. However, these differences did not translate into significant clinical or functional differences between groups in patient-related outcome measures, gait kinematics, kinetics, or spatio-temporal parameters at the 1-year mark. Both alignment techniques showed similar deviations from healthy gait patterns, particularly reduced knee flexion (mean ROM healthy 57.3°, KA 48.6°, MA 47.8°), and knee valgus during walking (mean maximal valgus healthy 15.2°, KA 10.5°, MA 9.5°). Notably, KA required fewer intraoperative soft tissue releases, suggesting procedural simplicity.

Conclusion: This study found no significant differences in clinical or functional outcomes between KA and MA despite distinct radiological alignment outcomes after 1-year follow-up. Both approaches yield comparable patient satisfaction and functional performance 1 year post-operatively. KA offers procedural advantages, specifically reduced soft tissue interventions.

Level of evidence: Level I.