Continuous outcomes of robotic-assisted total knee arthroplasty trials are statistically fragile

The purpose of this study was to calculate the continuous fragility index (CFI) of randomized controlled trials (RCTs) assessing outcomes following robotic-assisted total knee arthroplasty (RA-TKA).

MEDLINE, EMBASE, and CENTRAL were searched from inception to April 9, 2024, for RCTs assessing outcomes following RA-TKA compared to conventional total knee arthroplasty (C-TKA). The CFI was calculated for statistically significant outcomes. Multivariable linear regression was performed across the study-level median CFI and various study characteristics.

Seventeen studies (2,636 knees) were included in the final analysis. A total of 110 outcomes were eligible for analysis with a median CFI of 4.5 (IQR, 2.0-8.9). Radiographic outcomes were the most common significant outcome reported (33%, median CFI 7.6 [IQR 4.6-13.2]) followed by inflammatory markers (32%, median CFI 2.4 [IQR 1.0-3.0), operative characteristics (21%, median CFI 7.0 [IQR 4.2-13.7]), subjective outcomes (9%, median CFI 5.2 [IQR 3.1-8.3), and objective outcomes (5%, median CFI 3.1 [IQR 2.2-4.4]). There was a statistically significant difference across the aforementioned categories (p < 0.05). Multivariable linear regression demonstrated that larger sample size ( ß = 0.496, p < 0.0001) and inclusion of inflammatory markers (ß = 0.472, p = 0.015) were correlated with higher study-level median CFI.

Continuous outcomes across trials assessing RA-TKA versus C-TKA are relatively fragile compared to the orthopaedic literature to date. Radiographic outcomes were the most statistically robust category. The statistical robustness of findings may be limited by RCTs of a small sample size highlighting the importance of future collaborative, multicentre trials. LOE: I.