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.