Comparison of the Reliability and Gap Differences Between Using the Varus-Valgus Stress Technique and Paddles Technique in Pre-Resection Balancing Phase of Robotic-Assisted Total Knee Arthroplasty

Background: In robotic-assisted total knee arthroplasty, soft tissue tension assessment is critical during pre-resection balancing. This study compares the reliability and gap differences between the varus-valgus stress technique and the paddles technique, given the lack of comprehensive comparisons in the current literature. Methods: Prospective cohort study of 75 knees undergoing robotic-assisted total knee arthroplasty. During pre-resection balancing, joint tensioning assessments were performed by both an arthroplasty fellowship- trained surgeon and an experienced surgeon using both techniques. Four gap parameters were documented: extension medial, extension lateral, flexion medial, and flexion lateral widths. Interobserver reliability was evaluated using intraclass correlation coefficients. Incidence of >2 mm differences between assessors and mean gap differences between techniques were analyzed. Results: Both techniques demonstrated good-to-excellent interobserver reliability (intraclass correlation coefficient >0.8), with no statistically significant differences between fellowship-trained and experienced surgeons across all gap measurements (P > .05). However, technique choice significantly impacted gap measurements. The paddles technique consistently yielded wider lateral gaps compared to the varus-valgus stress technique: extension lateral gaps were 2.5-2.7 mm wider (P < .001) and flexion lateral gaps were 1.4-1.5 mm wider (P < .001). These differences were consistent regardless of surgeon experience level. Conclusions: Gap measurement differences are primarily determined by the assessment technique rather than surgeon experience. The paddles technique produces systematically wider lateral gaps compared to varus-valgus stress technique. Surgeons must account for these clinically significant differences when making balancing decisions, as technique choice impacts results; more than assessor experience level. Level of Evidence: Level II.