KSSTA - 2026-06-15 - Journal Article
No clinical and functional benefit after medial congruent compared to ultra congruent total knee arthroplasty at 1 year: A prospective randomized controlled study.
Schrednitzki D, Sina J, Lamarche A, Meissner N, Halder AM
Topics
Key Takeaway
MC and UC tibial inserts produced equivalent KSS scores (172.2 vs 174.0) and satisfaction rates (94.7% vs 92.1%) at 1 year, with no statistically significant difference on any outcome measure.
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Summary
This RCT compared MC vs UC tibial insert designs in 80 patients with varus knee OA undergoing primary TKA, with 76 completing 12-month follow-up. Both groups demonstrated significant within-group improvement in KSS, ROM, OKS, FJS-12, and HAAS, but no between-group difference was detected at any time point (all p>0.05). Satisfaction rates were 94.7% (MC) vs 92.1% (UC), with no significant difference in distribution (p=0.994).
Key Limitation
One-year follow-up cannot capture the primary mechanical concern distinguishing these designs — differential polyethylene wear and bearing stability under high-demand or long-term use.
Original Abstract
PURPOSE
Various conforming bearing designs are used during total knee arthroplasty (TKA), yet their impact on clinical outcomes remains uncertain. In recent years, the use of medial congruent (MC) and ultra congruent (UC) onlays has gained popularity. Hence, this study aims to evaluate the clinical outcomes of MC onlays compared to UC onlays in TKA.
METHODS
A prospective randomized controlled trial including 80 patients with advanced varus knee osteoarthritis undergoing primary TKA was conducted. Patients were randomly assigned to receive either a MC (n = 40) or UC insert (n = 40). Seventy-six patients (MC = 38; UC = 38) completed the 12-month follow-up. The primary outcome was the Knee Society Score (KSS), assessed preoperatively, at 6 weeks and 12 months postoperatively. Secondary outcomes included range of motion (ROM) and patient-reported outcome measures (PROMs): Oxford Knee Score (OKS), Forgotten Joint Score (FJS-12) and High-Activity Arthroplasty Score (HAAS) at 3, 6 and 12 months. Patient satisfaction, recommendation and willingness to undergo the procedure again were evaluated at 12 months. Radiographic alignment was assessed pre- and postoperatively.
RESULTS
Both groups showed significant improvement in the primary outcome KSS (MC: 87.6 ± 24.9 to 172.2 ± 20.3; UC: 94.2 ± 20.6 to 174.0 ± 23.7; p < 0.001 within both groups), ROM and PROMs without significant intergroup differences at any time point (all p > 0.05). The overall satisfaction rate (very satisfied + satisfied) was 94.7% in the MC group and 92.1% in the UC group with no significant difference in the distribution of satisfaction responses between groups (p = 0.994).
CONCLUSION
Both MC and UC inserts provided excellent clinical and functional outcomes 1 year after TKA, with high patient satisfaction and no statistically significant differences between designs. Thus, MC or UC designs may be chosen according to surgeon preference.
LEVEL OF EVIDENCE
Level I.