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 varusvalgus 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.