Becker's ASC Review

56 Executive Briefing Cost modeling approach Four variables were identified that could be affected by the use of traditional, reusable instruments vs. single-use Efficiency instruments for a TKA case: 1. Sterilization costs 2. Logistics for tray management (e.g. receiving, packing, storing) 3. OR turnover time (instrument setup and cleanup) 4. Treating surgical site infections during the first 90 days post- discharge These variables were subdivided into a resource variable (e.g. number of trays to sterilize per case) and a unit cost variable (e.g. cost of sterilizing one tray). A total of 200 sites (e.g. hospitals) and 500 cases per site were simulated (100,000 total cases) using the Monte Carlo technique, where values of each variable are picked from probability distributions to represent each unique case. In this study, some of the variables were only changed at the site level (e.g. cost of sterilizing one tray) so that they would be fixed across the 500 cases performed at that site. The rest of the variables were allowed to change on a case-by- case basis (e.g. number of trays used in each TKA case). The probability distributions were constructed for each of the model variables based on data from published clinical studies or estimates from expert panels, with different values for Efficiency vs. reusable instruments (Table 1). Costs were adjusted for inflation to 2018 U.S. dollars based on the U.S. medical care Consumer Price Index (CPI). Modeling Efficiency in OR turnover A second modeling technique examined the effect of OR turnover time on under- and over-utilization of the OR. Single-room OR blocking was assumed where a surgeon and the support team would be allotted the space for a full 8-, 10- or 12-hour day. Cases were assumed to be scheduled back-to-back with 2 hours allotted for each case, based on a mean turnover time of 38 minutes and mean procedure time of 79 minutes 6 . For example, an 8-hour OR block had 4 cases scheduled each day. The same Monte Carlo technique was used to determine the length of each procedure and turnover time for each simulated case. If the scheduled cases for the day finished with at least 2 hours to spare, an additional case could have been completed that day. If the scheduled cases took longer than the allotted time for the OR over the course of the full day, the extra time was considered as staff overtime. Cost savings with GMK Efficiency instruments Figure 2. Frequency distribution of cost savings by site. Approximately 75% of sites saved at least $750 per case, 50% saved at least $1,000 per case, and 25% saved over $1,200 per case. Based on this model, switching from reusable to Efficiency instruments translated to a mean cost savings of $1,003 per case. Approximately 75 percent of simulated healthcare providers saved at least $750 per case, 50 percent saved at least $1000 per case, and 25 percent saved over $1,200 per case. The smallest cost savings observed by a provider was $4.50 per case and the largest was $1,829 per case (Figure 2). Reductions in tray sterilization and loaner set management were the largest drivers for cost savings. On average, the sites that saved the most by switching to Efficiency instruments had significantly higher personnel costs for tray sterilization and tray management compared to the sites saving the least. The cost of OR time, the total OR turnover time, the average number of trays used per case, and the tray management time were not significantly different between the sites saving the most and the least. Also, changing the assumption of a 40 percent reduction in infection rates to a 20 percent reduction with Efficiency instruments did not significantly affect cost savings due to the low rates of peri- operative infections in TKA. Variable Instruments Instruments Values for Model (Mean ± SD) Associated Cost (Median; IQR) 90-day Infection Rate (%) Reusable Efficiency single use 0.58% ± 0.07% = 0.6 × RIIR* $30,020 / case ($19,104 – $47,033) Trays Used per Case (n) Reusable Efficiency single use 8 ± 2 1 ± 0 $57.87 / re-sterilized tray ($44.50 – $77.23) OR Turnover Time (min) Reusable Efficiency single use 38.4 ± 7.7 Time savings 17.5 ± 3.5 $5.72 / minute ($4.46 – $7.60) Tray Management Time (min) Reusable Efficiency single use 355 ± 71 80 ± 16 $1.03 / minute ($0.71 – $1.52) RIIR = Reusable Instrument Infection Rate; OR = operating room; SD = Standard deviation; IQR = Interquartile range * Assumes a 40% reduction in infection rate with single-use instruments Table 1. Model inputs for resource variables 6 Gadinsky, N. E., Manuel, J. B., Lyman, S. et al. Increased operating room time in patients with obesity during primary total knee arthroplasty: conflicts for scheduling. J Arthroplasty 2012; 27:1171-1176.

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