The Statistical Fragility of Patellar Resurfacing in Total Knee Arthroplasty: A Systematic Review of Randomized Controlled Trials

Background: Randomized controlled trials (RCTs) evaluating patellar resurfacing in total knee arthroplasty (TKA) have conflicting findings, with some reporting its efficacy and others demonstrating no clinical significance. The fragility index (FI), reverse FI (rFI), and fragility quotient (FQ) evaluated statistical fragility of outcomes in RCTs evaluating patellar resurfacing in TKA. Methods: The PubMed, Embase, and MEDLINE databases were systematically searched for RCTs (January 1, 2000, to August 1, 2023) assessing patellar resurfacing in TKA. Of the 226 RCTs screened, 19 studies were included for analysis. We calculated FI and rFI, which represent the number of outcome event reversals required to alter statistical significance for significant and nonsignificant outcomes, respectively. The outcome categories of interest included anterior knee pain, complications/adverse events, crepitus, reoperation, patient satisfaction, and clinical improvement. The FQ was determined by dividing the FI by the study sample size. Results: Across 46 outcomes, the median FI was 5 (interquartile range (IQR) 3 to 8) with a median FQ of 0.041 (IQR 0.025 to 0.063). There were nine outcomes that were statistically significant, with a median FI of 3 (IQR 2 to 8) and a FQ of 0.011 (IQR 0.0044 to 0.039). There were 37 outcomes that were nonsignificant, with a median rFI of 5 (IQR 4 to 7) and FQ of 0.043 (IQR 0.031 to 0.062). Notably, in 47.8% of all outcomes, the number of patients lost to follow-up was greater than the outcome's respective FI or rFI. Outcomes regarding patient satisfaction (FI 4.5) and anterior knee pain (FI 5) were most fragile. Conclusions: The outcomes of interest regarding patellar resurfacing from RCTs are statistically fragile, particularly significant outcomes and patient satisfaction outcomes. Data surrounding patellar resurfacing remain inconclusive, and combining P values with FI/FQ metrics may aid in interpreting patellar resurfacing findings. Future studies may mitigate fragility by obtaining higher follow-up rates and sample sizes. Level of Evidence: I.