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Hannah Wolford et al
Table 3. Comparison of Projected 2020 to 2030 Primary and Revision Hip and Knee Arthroplasties and Surgical Site Infections (SSIs) With and Without an Increasing Rate of Obesity in the Baseline Population
2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 Total
Hip Arthroplasties Increasing obesity rate 492,153 498,827 505,966 513,163 520,269 528,167 535,599 542,853 550,251 556,946 563,437 5,807,631 Stable obesity rate Difference
1,592 1,847 2,097 2,344 2,591 2,832 3,068 3,297 3,524 3,755 28,282
Hip SSIs Increasing obesity rate 2,693 Stable obesity rate Difference
2,583 110
2,748 2,616 132
2,805 2,651 154
2,862 2,687 175
2,919 2,722 197
2,980 2,761 219
3,039 2,799 240
3,097 2,836 261
3,157 2,874 283
3,212 2,908 304
3,266 2,941 325
32,778 30,378 2,400
Knee Arthroplasties Increasing obesity rate 674,187 688,618 703,574 718,031 732,332 747,413 761,366 774,253 785,882 797,411 808,183 8,191,250 Stable obesity rate Difference
Knee SSIs Increasing obesity rate 2,059 Stable obesity rate Difference
1,909 150
2,105 1,926 179
2,153 1,946 207
2,199 1,964 235
2,245 1,982 263
new and improved prevention strategies. Identifying facilities with a higher burden of SSIs will become increasingly important in future years as burden increases. Comprehensive guidelines on strategies to reduce SSIs were recently updated with specific recommenda- tions for infections following prosthetic joint arthroplasties that have the potential to reduce rates of these infections.29 Investment in these recommendations may decrease patientmorbidity and save substantial hospital costs. However, SSIs are relatively rare in comparison to other HAIs.
Using national estimates derived from the 2011 multistate point- prevalence survey for central-line–associated bloodstreaminfections (CLABSIs), we would expect 171,600 total CLABSIs across 11 years versus roughly 78,000 SSIs following hip and knee arthroplasty procedures alone.30However, SSIs are a significant component of the overall burden ofHAI costs, and they account for between 3 and 22 times the patient hospital costs of more common conditions such as CLABSIs, ventilator-associated pneumonia, catheter-associated urinary tract infections, and Clostridium difficile infections.31 Addi- tionally, SSIs continue to accrue costs long after the initial diagnosis and treatment. Yi et al14 found that patients who had SSI following hip and knee arthroplasty procedures required $53,470 in excess Medicare reimbursement in the 4 years following a procedure, in comparison to those without an SSI. Medicare will be responsible for much of the costs associated
with SSIs following hip and knee arthroplasty. In 2014, Medicare paid for 55% of knee arthroplasty claims and 59% of hip arthroplasties claims nationally,32 and our model shows that the majority of SSIs from 2020 to 2030 following arthroplasties will occur in a Medicare-eligible population (patients aged 65 and older). Multiplying the likely proportion of SSIs paid for by Medicare by excess Medicare reimbursement calculated by Yi et al, we found that Medicare will likely be responsible for >$2.4
2,294 2,003 291
2,339 2,021 318
2,382 2,038 344
2,421 2,052 369
2,460 2,065 395
2,497 2,078 419
25,154 21,984 3,170
billion in reimbursements attributable to SSIs from 2020 through 2030. Although we do not have an estimate for private payer reimbursement, extrapolating the Medicare reimbursement amount to the total population translates to $4.2 billion in reimbursement (by both private and Medicare insurance) attri- butable to SSIs following hip and knee arthroplasty.
Rate reduction impact
We project that achieving the HHS goal of a 30% reduction in the rate of SSIs would prevent >20,000 SSIs following hip and knee arthroplasties alone and may have substantial impact on sub- sequent patient morbidity and hospital costs. Reaching the goal could result in $712 million savings in Medicare reimbursement (assuming $53,470 in Medicare reimbursement per SSI).14 Notably, these infections represent only a small portion of the total number of SSIs. Extrapolating that cost number to the total population could result in a reduction of $1.2 billion in total reimbursement. Our analysis has several limitations that should be considered.
Our study assumed stable rates obtained from historical data and published literature for arthroplasties and SSIs, stratified by age, gender, and obesity status. Our infection rates relied on self- reported surveillance data from NHSN. We did not account for rate changes due to outside factors suggested by other studies including increasing demand for the surgery or comorbidities, such as diabetes, depression or cardiac arrhythmia,5–10 which we would expect to lead to increases in arthroplasties and SSIs (similar to our obesity analysis). Additionally, our arthroplasty rates did not include outpatient or same-day discharge surgeries (0.75%–6.2% of hip and knee arthroplasties) which are infrequent but may potentially increase in the future. Thus, our projections may have
490,818 497,235 504,119 511,066 517,925 525,576 532,767 539,785 546,954 553,422 559,682 5,779,349 1,335
637,982 645,427 653,436 661,052 668,595 676,913 684,270 690,744 696,182 701,618 706,473 7,422,692 36,205 43,191 50,138 56,979 63,737 70,500 77,096 83,509 89,700 95,793 101,710 768,558
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