Inter- and intra-operator variability in ligament balance measurements in total knee arthroplasty with the robotic navigation system (ROSA®): in vivo study

Purpose: This study quantifies the reproducibility of soft tissue laxity and gap measurements under manual stress, and implant positioning planning using the imageless ROSA® robotic system, by comparing a senior high-volume surgeon with a low-volume resident. Methods: In this single-center prospective study, 17 patients undergoing robotic-assisted total knee arthroplasty were evaluated. Intra- and inter-operator variability was assessed by recording intraoperative measurements and planning outcomes using a standardized protocol for functional alignment (FA). Results: Good-to-excellent reproducibility in soft tissue and gap assessments is demonstrated by both intra- and inter-operator measurements. Minor differences in planning parameters—including stylus height, femoral implant flexion, and the distal femoral cut—are observed, likely due to subjective high-volume surgeon adjustments. Conclusion: High reproducibility in soft tissue measurements and surgical planning across surgeons with different experience levels is shown by the ROSA® robotic system, while flexibility for individualized surgical strategies is retained.