Robotic Arm–Assisted Total Knee Arthroplasty Results in Smaller Femoral Components and Larger Tibial Baseplates Than the Manual Technique

Abstract

<h2>Abstract</h2><h3>Background</h3> Robotic systems for total knee arthroplasty (TKA) may utilize computed tomography three-dimensional modeling and intraoperative ligamentous balancing data to assist surgeons with implant size and position. This study evaluated the effect of such robotic systems on implant selection. <h3>Methods</h3> We reviewed 645 TKAs performed with a single prosthetic design at 2 academic medical centers between 2016 and 2022. A robotic system was utilized in 304 TKAs, 341 were conventionally instrumented. Implant sizing was compared between cohorts. Multivariate analyses assessed for confounding and effect modification on the basis of demographics. <h3>Results</h3> The 2 cohorts exhibited no significant differences in age (<i>P</i> = .33), weight (<i>P</i> = .29), or race (<i>P</i> = .24). The robotic-arm cohort had fewer women (58.9% vs 66.7% <i>P</i> = .04) and was taller on average (66.3 in vs 65.0 in <i>P</i> < .001). Mean polyethylene liner thickness was larger in the manual cohort (10.3 robotic and 10.6 manual; <i>P</i> < .00). On multivariate analysis, robotic-arm TKAs had larger tibial components (<i>P</i> < .001) and smaller femoral components (<i>P</i> = .017). <h3>Conclusions</h3> Robotic-arm assisted TKA with computed tomography–based three-dimensional planning was associated with a larger mean tibial component size and a smaller mean femoral component size when compared to conventionally instrumented TKAs. Observed differences likely reflect differences in the data informing implant size selection; effects on clinical outcomes warrant further study.