Comparison of Polyethylene Thickness and Constraint in Traditional and Robotic-Assisted Total Knee Arthroplasty

Abstract

Introduction. Thicker polyethylene inserts in total knee arthroplasty (TKA) may be associated with increased wear rates, a higher risk of implant failure, and the need for revision surgery. The authors of this study aimed to compare polyethylene insert thickness in robotic-assisted TKA versus conventional manual TKA. 

Methods. The authors conducted a cross-sectional study on patients with end-stage primary knee osteoarthritis who underwent TKA by a single fellowship-trained orthopedic surgeon over a two-year period. Patients with post-traumatic or inflammatory arthropathy or those undergoing revision arthroplasty were excluded. Demographics, implant manufacturer and type, and polyethylene insert thickness were recorded in an electronic database. Bivariate analyses, including t-tests, Mann-Whitney U tests, and Fisher’s exact tests were used to compare robotic-assisted and manual TKA procedures.

Results. Data from 222 patients were analyzed, with 111 in each group. The mean (standard deviation [SD]) age at surgery was similar between groups: 64.3 (8.2) years for robotic-assisted and 62.3 (8.8) years for the manual group (p=0.398). Polyethylene insert thickness differed significantly: the median was 9 mm (range 9-13 mm) in the robotic-assisted group versus 11 mm (range 9-16 mm) in the manual group (p<0.001). The most frequently used thickness was 9 mm, used in 70.3% (78/111) of robotic-assisted cases compared to 34.2% (38/111) of manual cases (p<0.001).

Conclusions. Robotic-assisted TKA was associated with significantly thinner polyethylene inserts compared to manual, suggesting more precise, bone-sparing femoral and tibial cuts. These findings may support the use of robotic-assisted techniques by orthopedic surgeons seeking to optimize implant positioning and longevity.