Unadjusted Patient Characteristics by Provider Group*
| Variable | Surgeon volume | Hospital volume | ||||
|---|---|---|---|---|---|---|
| Low | Medium | High | Low | Medium | High | |
| Mean age, yr | 67.6 | 68.1 | 66.0† | 69.0 | 67.8 | 65.5† |
| Comorbidity > 0, % | 19.4 | 16.6 | 17.1 | 19.2 | 17.4 | 16.3 |
| Comorbidity > 2, % | 7.3 | 5.0 | 5.0 | 5.1 | 5.8 | 4.6 |
| Males, % | 41.2 | 42.2 | 42.0 | 42.0 | 43.6 | 40.6 |
| No osteoarthritis, % | 10.4 | 7.0 | 7.5 | 7.0 | 6.6 | 8.6 |
| Discharged home, % | 36.3 | 43.0 | 33.5† | 45.4 | 41.3 | 31.8† |
| Mean hospital stay, d | 13.6 | 12.3 | 11.0† | 12.8 | 11.6 | 11.4† |
| Died during index hospitalization, % | 0.3 | 0.4 | 0.3 | 0.4 | 0.3 | 0.4 |
| Died within 3 mo, % | 1.0 | 0.7 | 0.7 | 0.6 | 0.7 | 0.8 |
| Died within 1 yr, % | 2.4 | 2.0 | 1.4 | 2.1 | 1.8 | 1.4 |
| Infection within 3 yr, % | 2.8 | 2.2 | 1.6 | 2.5 | 1.8 | 1.8 |
| Infection within 1 yr, % | 1.4 | 1.1 | 0.8 | 1.1 | 1.1 | 0.8 |
| Revision within 3 yr, % | 3.5 | 1.9 | 2.2 | 1.5 | 2.0 | 2.5 |
| Revision within 1 yr, % | 1.4 | 1.1 | 1.2 | 0.6 | 1.2 | 1.4† |
| Complications during index hospitalization, % | 6.9 | 8.7 | 9.0 | 6.8 | 9.2 | 8.9 |
| Deep vein thrombosis within 3 mo, % | 3.5 | 3.5 | 3.3 | 2.3 | 3.0 | 3.9‡ |
| Urinary tract infection during index hospitalization, % | 2.4 | 3.0 | 2.7 | 4.4 | 3.2 | 1.9† |
↵* Statistical comparisons were made by the Kruskal–Wallis one-way analysis of variance or the Pearson χ2 test, depending on whether the variable of interest represented a continuous quantity (comparison of mean values across groups) or a dichotomous variable (comparison of the percentage of positive cases across groups).
↵† p ≤ 0.01
↵‡ 0.01 < p < 0.05