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Table 5 Comparison of baseline characteristics by surgical site infection status pre- and post-match in the total knee arthroplasty cohort

From: Economic burden of surgical site infections within the episode of care following joint replacement

   Pre-match   Post-match
Total No SSI SSI no SSI
N 158,516 157,376 1140 1140
Mean age (SD) 66.25 (9.7) 66.3 (9.7) 65.3 (10.0) 65.8 (9.7)
Sex (%)
 Male 61,012 (38.5) 60,456 (38.4) 556 (48.8) 562 (49.3)
 Female 97,504 (61.5) 96,920 (61.6) 584 (51.2) 578 (50.7)
Payer (%)
 Medicare 90,700 (57.2) 90,040 (57.2) 660 (57.9) 672 (59.0)
 Medicaid 4607 (2.9) 4535 (2.9) 72 (6.3) 69 (6.1)
 Private insurance 55,590 (35.1) 55,243 (35.1) 347 (30.4) 349 (30.6)
 Self-pay 636 (0.4) 626 (0.4) 10 (0.9) 15 (1.3)
 No charge 166 (0.1) 163 (0.1) 3 (0.3) 4 (0.4)
 Other 6632 (4.2) 6585 (4.2) 47 (4.1) 31 (2.7)
 Unknown 185 (0.1) 184 (0.1) 1 (0.1) 0(0)
Hospital bedsize (%)
 Small 28,404 (17.9) 28,223 (17.9) 181 (15.9) 172 (15.1)
 Medium 42,309 (26.7) 41,997 (26.7) 312 (27.4) 298 (26.1)
 Large 87,803 (55.4) 87,156 (55.4) 647 (56.8) 670 (58.8)
Zip income quartile (%)  
 0–25th percentile 33,248 (21.0) 32,992 (21.0) 256 (22.5) 268 (23.5)
 26th–50th percentile 42,535 (26.8) 42,237 (26.8) 298 (26.1) 286 (25.1)
 51st–75th percentile 43,118 (27.2) 42,810 (27.2) 308 (27.0) 312 (27.4)
 76th–100th percentile 37,061 (23.4) 36,799 (23.4) 262 (23.0) 264 (23.2)
 Unknown 2554 (1.6) 2538 (1.6) 16 (1.4) 10 (0.9)
Hospital teaching status (%)
 Metropolitan non-teaching 78,155 (49.3) 77,586 (49.3) 569 (49.9) 581 (51.0)
 Metropolitan teaching 64,844 (40.9) 64,391 (40.9) 453 (39.7) 461 (40.4)
 Non-metropolitan teaching 15,517 (9.8) 15,399 (9.8) 118 (10.4) 98 (8.6)
Comorbidity Index (%)
 0–1 124,721 (78.7) 123,890 (78.7) 831 (72.9) 833 (73.1)
 2–3 12,378 (7.8) 12,273 (7.8) 105 (9.2) 100 (8.8)
 > 3 21,417 (13.5) 21,213 (13.5) 204 (17.9) 207 (18.2)