Purpose: Ligament tension balance is essential for successful and long-term implant survival of total knee arthroplasty (TKA). Conventional manual tensioning methods are subjective and vary with the surgeon experience. This study evaluated the inter- and intra-rater reliability of pre-resection ligament tension assessments using an imageless robotic-assisted TKA system.
Methods: In this prospective study, 24 patients (30 knees) with end-stage knee osteoarthritis underwent CORI-assisted TKA from September 2024 to February 2025. Three specialist and three trainee surgeons each performed three repeated varus and valgus stress assessments across flexion and extension. Each medial and lateral gap measurement was recorded. Intraclass correlation coefficients (ICCs) were calculated with a two-way mixed-effects and two-way random-effects model.
Results: Both specialists and trainees demonstrated excellent intra- and inter- rater reliability (ICC > 0.90) for medial and lateral gaps in extension and medial gap in flexion. Flexion lateral reliability was good-to-excellent for trainees (ICC = 0.873, 95% CI: 0.784–0.933) and moderate-to-excellent for specialists (ICC = 0.838, 95% CI: 0.729–0.913).
Conclusions: Pre-resection ligament tension assessment with an imageless robotic system yields high inter- and intra-rater reliability, reducing variability linked to surgeon experience. Digital tensioners may standardize soft tissue balancing in TKA, potentially improving surgical outcomes and reproducibility.
Evidence Level: Level III, prospective quasi-experimental study.
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2026 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.
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