Table 1.
Characteristics of the TKA (ICD-9 code 8154) patients from the 2013 NRD.
| Risk factors | Before propensity matching |
After propensity matching |
||||||
|---|---|---|---|---|---|---|---|---|
| Medicaid, N = 8372 | Other insurance, n = 268,261 | P Value | Standardized difference | Medicaid, n = 8372 | Other insurance, n = 8372 | P valuea | Standardized differenceb | |
| Age, years (mean ± SD) | 56.7 ± 9.4 | 66.7 ± 9.7 | <.0001 | 1.055 | 56.7 ± 9.4 | 56.5 ± 9.6 | <.001 | 0.014 |
| Female sex | 6072 (72.5%) | 165,227 (61.6%) | <.0001 | 0.234 | 6071 (72.5%) | 6129 (73.2%) | .004 | 0.016 |
| Severity of illness (major/extreme loss vs other) | 549 (6.6%) | 13,685 (5.1%) | <.0001 | 0.062 | 547 (6.5%) | 477 (5.7%) | <.001 | 0.035 |
| Discharged to skilled facility | 2118 (25.3%) | 75,028 (28.0%) | <.0001 | 0.061 | 2118 (25.3%) | 2142 (25.6%) | .261 | 0.007 |
| Smoking | 2711 (32.4%) | 59,997 (22.4%) | <.0001 | 0.226 | 2710 (32.4%) | 2664 (31.8%) | .038 | 0.012 |
| Comorbidities | ||||||||
| AIDS | 9 (0.1%) | 46 (0.0%) | <.0001 | 0.036 | 9 (0.1%) | 4 (0.0%) | .166 | 0.021 |
| Alcohol abuse | 201 (2.4%) | 2490 (0.9%) | <.0001 | 0.115 | 201 (2.4%) | 148 (1.8%) | <.001 | 0.044 |
| Deficiency anemia | 1049 (12.5%) | 29,855 (11.1%) | <.0001 | 0.043 | 1048 (12.5%) | 1055 (12.6%) | .730 | 0.003 |
| Rheumatoid arthritis | 458 (5.5%) | 11,102 (4.1%) | <.0001 | 0.062 | 457 (5.5%) | 414 (4.9%) | .008 | 0.023 |
| Chronic blood loss anemia | 92 (1.1%) | 3227 (1.2%) | .388 | 0.010 | 92 (1.1%) | 90 (1.1%) | .821 | 0.002 |
| Congestive heart failure | 203 (2.4%) | 6289 (2.3%) | .635 | 0.005 | 203 (2.4%) | 170 (2.0%) | .019 | 0.027 |
| Chronic pulmonary disease | 2100 (25.1%) | 38,992 (14.5%) | <.0001 | 0.267 | 2100 (25.1%) | 2056 (24.6%) | .055 | 0.012 |
| Coagulopathy | 163 (1.9%) | 5493 (2.0%) | .520 | 0.007 | 163 (1.9%) | 134 (1.6%) | .025 | 0.026 |
| Depression | 1676 (20.0%) | 34,767 (13.0%) | <.0001 | 0.191 | 1675 (20.0%) | 1658 (19.8%) | .416 | 0.005 |
| Diabetes | 2179 (26.0%) | 57,641 (21.5%) | <.0001 | 0.107 | 2179 (26.0%) | 2152 (25.7%) | .222 | 0.007 |
| Peripheral vascular disorders | 101 (1.2%) | 6613 (2.5%) | <.0001 | 0.094 | 101 (1.2%) | 67 (0.8%) | <.001 | 0.041 |
| Drug abuse | 257 (3.1%) | 1437 (0.5%) | <.0001 | 0.191 | 256 (3.1%) | 194 (2.3%) | <.001 | 0.046 |
| Weight loss | 47 (0.6%) | 1130 (0.4%) | .053 | 0.020 | 47 (0.6%) | 42 (0.5%) | .553 | 0.008 |
| Infection | 118 (1.4%) | 1977 (0.7%) | <.0001 | 0.065 | 118 (1.4%) | 114 (1.4%) | .728 | 0.004 |
a
McNemar's test (a chi-square test for paired proportions). The difference in paired proportions is small for all covariates but statistically significant for several covariates because of the large sample size.
b
A standardized difference less than 0.10 suggests negligible difference in the mean or prevalence of a covariate between the 2 insurance groups.