The statistical robustness of randomized controlled trials (RCTs) assessing robotic-assisted total knee arthroplasty (TKA) compared to conventional TKA remains unclear. The continuous fragility index (CFI) assesses an outcome's statistical robustness by calculating the number of patients required to render a statistically significant outcome no longer significant. The purpose of this study was to calculate the CFI of RCTs assessing outcomes following robotic-assisted TKA (RA-TKA). MEDLINE, EMBASE and CENTRAL were searched from inception to April 9, 2024 for RCTs assessing outcomes following robotic-assisted TKA compared to conventional technique. The CFI was calculated for statistically significant outcomes. Outcomes were categorized based on (1) outcome type, (2) duration of an outcome's follow-up as well as (3) robot utilized. 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. Median age of patients was 66.9 years (interquartile range IQR 65.4–68.4 years). A total of 110 outcomes were eligible for analysis with a median CFI of 4.5 (IQR 1.1–8.0). Radiographic outcomes were the most commonly reported (33%, median CFI 7.6 IQR 3.3–11.9) followed by inflammatory markers (32%, median CFI 2.4 IQR 1.4–3.4), operative characteristics (21%, median CFI 7.0 [IQR 2.3–11.8), subjective outcomes (9%, median CFI 5.2 IQR 2.6–7.9) and objective outcomes (5%, median CFI 3.1 [IQR 2.0 to 4.2). There was a statistically significant difference across the aforementioned categories (p 0.05). Eligible outcomes reported for the ROBODOC had the highest median CFI at 8.5 (IQR, 4.1–16.2) while outcomes reported for the YUANHUA had the lowest at 2.9 (IQR, 1.6–6.9) (p < 0 .05). Multivariable linear regression demonstrated that larger sample size (ß=0.47, p < 0 .0001) and lower journal impact factor (ß= −1.9, p=0.0014) 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 commonly reported significant outcomes and the most statistically robust across RCTs assessing robotic-assisted TKA compared to conventional TKA. An inverse correlation existed between study-level CFI and journal impact factor indicating that RCTs published in higher quality journals may not necessarily be more statistically robust. Future trials should maximize their sample size to ensure robustness of statistically significant findings.
Khalik et al. (Wed,) studied this question.