Interobserver Variability of Intraoperative Soft Tissue Laxity Assessment in Robotic-Assisted Total Knee Arthroplasty Using the ROSA System.

Abstract

This study evaluated the interobserver reliability of intraoperative soft tissue laxity assessment during robotic-arm assisted total knee arthroplasty (TKA) using the Robotic Surgical Assistant (ROSA) system. Although robotic systems have improved the precision of bone alignment, the reproducibility of soft tissue evaluations-critical for achieving joint balance-remains uncertain. We retrospectively analyzed 37 knees from 30 patients who underwent ROSA-assisted TKA. Soft tissue laxity was manually assessed under varus and valgus stress at extension and 90° of knee flexion. Two parameters were recorded: joint gap widening and hip-knee angle (HKA). Interobserver agreement was evaluated using intraclass correlation coefficients (ICC), Pearson's correlation coefficients, and Bland-Altman plots. Angular measurements, particularly HKA at extension, demonstrated excellent interobserver reliability (ICC = 0.94). In contrast, gap-based measurements showed greater variability, with lateral laxity under varus stress at extension demonstrating poor reliability (ICC = 0.31). Agreement between observers was generally stronger at extension than at 90° flexion. Contralateral assessments showed better consistency. While robotic systems improve alignment accuracy in TKA, intraoperative soft tissue laxity evaluation remains prone to interobserver variability. Gap-based measurements are less reliable than angular assessments, underscoring the need for standardized evaluation methods to improve consistency in soft tissue evaluation during robotic TKA.