2025 ISAKOS Biennial Congress Paper
Precision and Accuracy of Polyethylene Thickness in Total Knee Arthroplasty: A Comparison Between Conventional and Robotic Assisted Techniques
Kory B. Dylan Pasko, BS, San Clemente, ca UNITED STATES
Cooper Ehlers, MD, MS, San Diego, ca UNITED STATES
Georgetown University School of Medicine, Washington, Washington DC, UNITED STATES
FDA Status Not Applicable
Summary
Increased polyethylene thickness is associated with increased rate of revision in primary total knee arthroplasty and increased bone loss. Robotic assisted total knee arthroplasty improved polyethylene implant accuracy and precision thus leading to increased bone preservation.
Abstract
Introduction
Increased polyethylene thickness is associated with increased rate of revision in primary total knee arthroplasty (TKA) and increased bone loss. The purpose of this study is to determine implant accuracy to the preoperatively planned polyethylene thickness as defined by mean difference between the preoperatively planned polyethylene thickness and the final implant polyethylene thickness used (mean Δ PT). We also determined implant precision as defined by variance in polyethylene thickness used. Polyethylene accuracy and precision were compared when a conventional total knee arthroplasty (C-TKA) using mechanical instrumentation was performed to robotic assisted total knee arthroplasty (RA-TKA) to determine if any difference existed between the two groups.
Methods
A retrospective review of 815 patients undergoing TKA between March 2018 and July 2023 by a single surgeon at a single institution was performed. A statistical analysis was undertaken to compare patients who underwent C-TKA versus patients who underwent RA-TKA. Preoperatively, planned polyethylene thickness for all TKAs was 9 mm. Primary outcome measures collected were preoperatively planned polyethylene thickness and final implant polyethylene thickness. Average polyethylene thickness, mean deviation from the plan, and variance were compared between the two groups.
Results
A total of 815 patients underwent TKA with 404 patients (49.6%) in the C-TKA group and 411 patients (50.4%) in the RA-TKA group. When comparing the RA-TKA group to the C-TKA group there was no difference in mean age or gender (p=0.4, p=0.52, chi statistic 0.404). Mean polyethylene thickness was 10.7 mm in C-TKA and was 9.3 mm in RA-TKA (p<0.05). Mean deviation from planned polyethylene thickness was 1.7 mm in the C-TKA group and was 0.3 mm in the RA-TKA group (p < 0.05). Variance in the C-TKA group (SD=1.179) was greater than the RA-TKA group (SD=0.608) (F statistic = 0.266, p<0.05).
Conclusions
Robotic assisted total knee arthroplasty (RA-TKA) improved polyethylene implant accuracy and precision thus leading to increased bone preservation. Further studies are needed to investigate whether this improved accuracy and precision decreases future revision rate.