Soft Tissue Balance Profiles Differ Between Manual and Robotically Assessed Gaps in Total Knee Arthroplasty

This study examines the agreement and error between manual gap assessment, and assessment with a robotic soft-tissue tensioning device in total knee arthroplasty across multiple surgeons.

517 consecutive robotic-assisted TKAs were retrospectively reviewed across six surgeons following ethics approval. Robotic and manual mediolateral (ML) balance and medial and lateral gaps were compared using Intraclass Correlation Coefficient (ICC). ΔML balance (manual-robotic) was compared between right and left knees.

Manual and robotic ML balance showed poor agreement (ICC = 0.368). Surgeons had low to moderate correlations (ICC range: 0.152-0.633) and significant differences throughout flexion. Four measured greater medial gaps manually and two measured greater lateral gaps compared to robotics. All showed significant ΔML balance differences between the leg sides (p < 0.05), with surgeon-specific variations in gap patterns.

Manual ML balance correlated poorly and differed significantly from robotic assessment, with surgeon-specific variation. Surgeons should appreciate the variability in subjective versus objective gap measurements.