Medial-pivot total knee arthroplasty demonstrates more constrained mid-flexion gait kinematics than posterior-stabilised total knee arthroplasty under standardised soft-tissue balancing: A randomised controlled trial with a healthy reference cohort.
rct · Level II
Where this comes from
- Record sourced from PubMed, PMID 42164843.
- Also identified by DOI 10.1002/jeo2.70752 and PMC identifier 13184998.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Most contemporary total knee arthroplasty (TKA) designs aim to replicate native kinematics, yet the independent contribution of implant geometry to dynamic stability remains unclear when soft-tissue balance is standardised. We compared medial-pivot (MP) and posterior-stabilised (PS) TKA implanted under a uniform medial-tight balancing protocol and contrasted both with healthy knees. Thirty-six patients with medial osteoarthritis were randomised to MP (EVOLUTION®) or PS (Persona®) TKA. All procedures used a medial parapatellar approach, modified measured resection and calibrated medial-tight balancing. At 1 year, knee injury and osteoarthritis outcome sore (KOOS) and knee society score (KSS) were recorded and three-dimensional gait kinematics were assessed. Femoral anterior-posterior translation (FAPT), femoral medial-lateral translation (FMLT) and tibial rotation angle (TRA) were quantified using a projection-based algorithm. A healthy reference cohort of 25 young adults (50 knees) completed the identical gait protocol. KOOS and KSS improved significantly in both TKA groups with no between-group differences. Maximum stance-phase FAPT (% body height) differed significantly among groups (analysis of variance [ANOVA] <i>p</i> < 0.01), with smaller excursions in MP TKA (0.8 ± 0.6) than PS TKA (1.9 ± 1.0) and healthy knees (1.9 ± 0.8). Maximum FMLT (% body height) also differed (ANOVA <i>p</i> < 0.01); MP TKA demonstrated smaller translations (0.9 ± 0.5) than PS TKA (2.4 ± 1.1), while PS TKA exhibited greater translations than healthy knees (1.3 ± 0.7). Maximum internal TRA (degrees) differed significantly (ANOVA <i>p</i> < 0.01); MP TKA showed greater internal rotation (4.1 ± 2.2) than PS TKA (2.8 ± 1.7), whereas both were reduced relative to healthy knees (12.0 ± 4.5). With identical medial-tight balancing, implant geometry independently influenced gait kinematics. MP TKA exhibited the most constrained translational behaviour, whereas both TKA designs showed reduced tibial rotation relative to healthy knees despite similar clinical outcomes. These findings highlight the biomechanical trade-off between reproducing native kinematics and adopting implant-guided stability. Level I, randomised controlled trial.