Archives of Orthopaedic and Trauma Surgery - 2026-08-22 - Journal Article
Elective arthroplasty on "high-risk" calendar dates: no evidence for worse outcomes in 43,000 procedures.
Walter N, Lowenberg DW, Heiss C, Lau EC, Rupp M
Topics
Key Takeaway
Among 945 arthroplasties performed on Friday the 13th, hazard ratios for aseptic revision (0.80), septic revision (0.83), and mortality (1.00) were not significantly different from control dates.
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Summary
This study asked whether primary THA and TKA performed on superstition-associated calendar dates (e.g., Friday the 13th) carry higher risks of aseptic revision, septic revision, or mortality. Using Medicare 5% sample data (2009–2019) with Fine-Gray competing-risk and multivariable Cox regression models, 945 arthroplasties on Friday the 13th were compared to control-date procedures. No significant differences were found in any outcome, and procedure volumes were also unchanged on superstition-associated dates.
Key Limitation
The 5% Medicare sample restricts the Friday the 13th cohort to 945 procedures, leaving the study underpowered to exclude small but real differences in low-incidence endpoints such as septic revision (HR 0.83, 95% CI 0.31–2.25).
Original Abstract
BACKGROUND
Concerns regarding the timing of elective surgery remain common among patients and may influence surgical scheduling. Superstition-associated calendar dates such as Friday the 13th are frequently perceived as "high-risk" time points, yet evidence regarding their impact on arthroplasty outcomes is lacking. This study investigated whether primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) performed on these dates are associated with differences in revision risk, mortality, or procedure frequency.
METHODS
A nationwide retrospective cohort study was conducted using Medicare physician service records (2009-2019). Primary THA and TKA procedures were identified in a 5% sample of Medicare beneficiaries aged ≥ 65 years. Outcomes included aseptic revision, septic revision, and mortality. Competing-risk survival analyses (Fine-Gray) and multivariable Cox regression models adjusted for demographic, clinical, and socioeconomic covariates were applied. Procedure volumes were compared between superstition-associated and control dates.
RESULTS
A total of 945 arthroplasties were performed on Fridays falling on the 13th. No significant differences were observed in aseptic revision, septic revision, or mortality compared with control dates. For Friday the 13th, hazard ratios were 0.80 (95% CI 0.44-1.47) for aseptic revision, 0.83 (95% CI 0.31-2.25) for septic revision, and 1.00 (95% CI 0.83-1.19) for mortality. Procedure volumes did not differ significantly between superstition-associated and control dates.
CONCLUSION
In this large registry-based study, the timing of elective total joint arthroplasty on superstition-associated calendar dates was not associated with increased complication risk, mortality, or changes in procedure volume. These findings may support evidence-based patient counselling and surgical scheduling in elective arthroplasty.