Superstition in arthroplasty: does a suspicious size or surgery date have a higher revision rate? A Dutch arthroplasty register study.

Background and purpose:  There are still strong beliefs in medicine concerning things that bring "bad luck." It is unclear whether a suspicious component size or surgery date is related to "bad luck" in orthopedic surgery. We aimed to examine: (i) if a potentially unlucky femoral stem size 13 in total hip arthroplasty (THA), and (ii) if a possible unlucky surgery date, Friday 13th, in THA and total knee arthroplasty (TKA) have a higher revision rate.

Methods:  We analyzed 611,050 THAs and TKAs, performed in the past 13 years using Dutch Arthroplasty Register data. The revision rate of uncemented femoral stem size 13 (Corail and Taperloc) in THA was compared with all other stem sizes of the same type. Furthermore, the revision rate of THA and TKA implanted on Friday 13th was compared with all other days and with other Fridays. Both were performed using competing risk analyses with death as competing risk and cause-specific multivariable Cox proportional hazard regression analyses.

Results:  The use of an uncemented Corail or Taperloc femoral stem size 13 in THA was associated with a lower revision rate (3.0%, 95% confidence interval [CI] 2.3-4.0) compared with the revision rate of other femoral stem sizes (3.5%, CI 3.3-3.8) (hazard ratio [HR] 0.76, CI 0.65-0.87). TKA procedures on Friday 13th were not associated with increased revision rate (5.2%, CI 4.1-6.7) compared with procedures on other days (6.0%, CI 5.9-6.2) or on other Fridays (5.8%, CI 5.4-6.2) (HR 1.03, CI 0.80-1.32 and HR 1.01, CI 0.79-1.30, respectively). For THA, procedures on Friday 13th were associated with a higher revision rate (5.1%, CI 3.9-6.6) compared with procedures on other days (4.6%, CI 4.5-4.8) (HR 1.32, CI 1.04-1.67) but not compared with procedures on other Fridays (4.8%, CI 4.4-5.1) (HR 1.24, CI 0.97-1.58).

Conclusion:  Based on national arthroplasty registry data, femoral stem size 13 in THA was associated with a lower revision rate. TKA procedures on Friday 13th were not associated with increased revision rate; however, in THA there seems to be an increased risk of revision in THA procedures performed on Friday 13th compared with other days, but not when compared with other Fridays.