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

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.