Clinical outcomes and patient-reported joint noise after total knee arthroplasty using saddle-shaped...

Different posterior cruciate ligament-sacrificing total knee arthroplasty (TKA) systems use distinct stabilization concepts, but their comparative clinical outcomes, including joint noise and knee flexion, remain unclear. We aimed to compare clinical outcomes, including noise and flexion, between the saddle-shaped rotating platform (ROCC) and bi-cruciate-stabilized (BCS) TKA. We hypothesized that the ROCC implant-surgical system would be associated with lower patient-reported noise, whereas the BCS implant-surgical system would be associated with greater flexion.

This retrospective propensity score-matched cohort study analyzed 556 consecutive primary TKAs for primary osteoarthritis (April 2017-April 2023). Patients with prior ligament surgery, additional ipsilateral procedures, or neurological disorders were excluded. Propensity score matching (1:1) for age, sex, body mass index, preoperative flexion, Knee Injury and Osteoarthritis Outcome Score (KOOS), and the University of California, Los Angeles activity score yielded 176 ROCC-BCS pairs. The primary outcome was KOOS-Pain score. Exploratory secondary outcomes included change in KOOS-Pain score, attainment of the KOOS-Pain minimal clinically important difference (MCID) (responder analysis), Forgotten Joint Score-12 (FJS), noise score (0-4), and maximum flexion. Spearman's ρ was used to assess correlations among flexion, noise, KOOS, and FJS. Group values are reported as medians unless otherwise indicated.

Median follow-up was 36 months. For the primary outcome, KOOS-Pain was higher with ROCC than with BCS (94 versus 89; matched-pair difference, 4.2 points; 95% confidence interval, 1.4 to 8.3; p = 0.005), but the difference was below the 18-point MCID. In exploratory responder analysis, KOOS-Pain MCID attainment was higher with ROCC (90% versus 82%). Among secondary outcomes, FJS was higher with ROCC (56 versus 48), noise scores were lower with ROCC (0 versus 1), and flexion was higher with BCS despite identical medians of 130°. Noise correlated negatively with KOOS and FJS (ρ = -0.24 to -0.34), whereas flexion showed negligible correlations.

ROCC was associated with modestly higher KOOS-Pain scores and lower patient-reported noise, but broader PROM findings were mixed. The KOOS-Pain difference was below the MCID, and its clinical relevance remains uncertain. These midterm findings may inform counseling on implant-surgical system trade-offs but require confirmation in broader prospective cohorts.