Table 1. Study Sample Description, Overall and by Primary Indication for Surgery, 2009-2011.
| Total (N=34311) | Osteoarthritis (N=33815) | Rheumatoid Arthritis (N=496) | P Value | |||||
|---|---|---|---|---|---|---|---|---|
|
| ||||||||
| Total N | N | % | N | % | N | % | ||
| TJA | THA | 11615 | 33.9 | 11448 | 33.9 | 167 | 33.7 | 0.931 |
| TKA | 22696 | 66.2 | 22367 | 66.2 | 329 | 66.3 | ||
| Operative year | 2009 | 10389 | 30.3 | 10233 | 30.3 | 156 | 31.5 | 0.316 |
| 2010 | 11751 | 34.3 | 11571 | 34.2 | 180 | 36.3 | ||
| 2011 | 12171 | 35.5 | 12011 | 35.5 | 160 | 32.3 | ||
| Age category, years | <65 | 13516 | 39.4 | 13237 | 39.2 | 279 | 56.3 | <0.001 |
| ≥65 | 20795 | 60.6 | 20578 | 60.9 | 217 | 43.8 | ||
| Female gender | 21057 | 61.4 | 20694 | 61.2 | 363 | 73.2 | <0.001 | |
| Race1 | White | 23765 | 69.3 | 23542 | 69.6 | 223 | 45.0 | <0.001 |
| Hispanic | 4601 | 13.4 | 4455 | 13.2 | 146 | 29.4 | ||
| Black | 3115 | 9.1 | 3049 | 9.0 | 66 | 13.3 | ||
| Asian | 2168 | 6.3 | 2114 | 6.3 | 54 | 10.9 | ||
| Other/Multi | 615 | 1.8 | 609 | 1.8 | 6 | 1.2 | ||
| BMI category1, kg/m2 | <30 | 17363 | 50.6 | 17071 | 50.5 | 292 | 58.9 | <0.001 |
| 30-34 | 9648 | 28.1 | 9537 | 28.2 | 111 | 22.4 | ||
| ≥35 | 7288 | 21.2 | 7195 | 21.3 | 93 | 18.8 | ||
| ASA category1 | 1-2 | 20163 | 58.8 | 19915 | 58.9 | 248 | 50.0 | <0.001 |
| ≥3 | 13920 | 40.6 | 13674 | 40.4 | 246 | 49.6 | ||
| Diabetes | 8220 | 24.0 | 8125 | 24.0 | 95 | 19.2 | 0.012 | |
| Deficiency anemias* | 4238 | 12.4 | 4115 | 12.2 | 123 | 24.8 | <0.001 | |
| Surgeon TJA fellowship | 13593 | 39.6 | 13362 | 39.5 | 231 | 46.6 | 0.001 | |
| Hospital yearly volume, cases/yr | <100 | 1830 | 5.3 | 1807 | 5.3 | 23 | 4.6 | 0.637 |
| 100-199 | 13588 | 39.6 | 13397 | 39.6 | 191 | 38.5 | ||
| ≥200 | 18893 | 55.1 | 18611 | 55.0 | 282 | 56.9 | ||
| Surgeon yearly volume, cases/yr | <20 | 3159 | 9.2 | 3114 | 9.2 | 45 | 9.1 | 0.634 |
| 20-49 | 14507 | 42.3 | 14287 | 42.3 | 220 | 44.4 | ||
| ≥50 | 16645 | 48.5 | 16414 | 48.5 | 231 | 46.6 | ||
| Discharge disposition1 | Home | 27020 | 78.8 | 26629 | 78.8 | 391 | 78.8 | 0.968 |
| Other | 7216 | 21.0 | 7112 | 21.0 | 104 | 21.0 | ||
| LOS categories, days1 | ≤2 | 13054 | 38.1 | 12888 | 38.1 | 166 | 33.5 | 0.216 |
| 3 | 15795 | 46.0 | 15548 | 46.0 | 247 | 49.8 | ||
| 4 | 3510 | 10.2 | 3457 | 10.2 | 53 | 10.7 | ||
| ≥5 | 1880 | 5.5 | 1852 | 5.5 | 28 | 5.7 | ||
| Intra-operative complications | Surgical | 1497 | 4.4 | 1476 | 4.4 | 21 | 4.2 | 0.887 |
| Non-surgical | 281 | 0.8 | 277 | 0.8 | 4 | 0.8 | 0.975 | |
Missing data: race (n=47, <0.1%), BMI (n=12, <0.1%), ASA (n=228, <0.7%), discharge disposition (n=71, 0.2%), LOS (n=72, 0.2%)
TJA=Total Joint Arthroplasty. THA=Total Hip Arthroplasty. TKA= Total Knee Arthroplasty. BMI=Body Mass Index. ASA=American Society of Anesthesiologists. LOS=Length of Stay.
Deficiency Anemia: one of the comorbidities from the Elixhauser's index, included here due to the level of significance in analyses. Elixhauser's index includes 29 comorbidities, as follows: Hypertension, chronic pulmonary disease, hypothyroidism, deficiency anemias, renal failure, psychoses, fluid and electrolyte disorders, depression, peripheral vascular disease, rheumatoid arthritis/collagen vascular disorders, valvular disease, other neurological disorders, chronic blood loss anemia, congestive heart failure, liver disease, coagulopathy, alcohol abuse, solid tumor w/out metastasis, pulmonary circulation disease, drug abuse, weight loss, paralysis, lymphoma, metastatic cancer, acquired immune deficiency syndrome, peptic ulcer disease with bleeding, diabetes* (without complications), diabetes* (with complications), and obesity*. *These 3 conditions were not used from the algorithm due to availability of more robust data sources for these measures: diabetes status is available from regional Kaiser Permanente diabetes registries and obesity from the patients' electronic medical records body mass index (BMI) assessments.