Characteristics of patients whose surgeries had the least amount of overlap (bottom 40% of patients with overlapping surgeries) and the most amount of overlap (top 10% of patients with overlapping surgeries).
| Variable | Least Overlap (N = 520) | Most Overlap (N = 131) | P Value |
| Age (y), mean (range) | 60.30 (24–88) | 63.90 (26–87) | 0.001 |
| Gender, n (%) | 0.96 | ||
| Male | 225 (43.3%) | 57 (43.5%) | |
| Female | 295 (56.7%) | 74 (56.5%) | |
| Race, n (%) Asian | 6 (1.2%) | 1 (0.8%) | 0.55 |
| Black | 55 (10.6%) | 12 (9.2%) | |
| White | 441 (84.8%) | 117 (89.3%) | |
| Hispanic | 4 (0.8%) | 0 (0%) | |
| Unknown | 10 (1.9%) | 0 (0%) | |
| Other | 2 (0.4%) | 1 (0.8%) | |
| East Indian | 2 (0.4%) | 0 (0%) | |
| Insurance, n (%) | 0.017 | ||
| Commercial | 20 (3.8%) | 2 (1.5%) | |
| Medicare | 213 (41.0%) | 73 (55.7%) | |
| Medicaid | 26 (5.0%) | 4 (3.1%) | |
| Managed care | 192 (36.9%) | 33 (25.2%) | |
| Blue cross | 69 (13.3%) | 19 (14.5%) | |
| Tobacco use within past 12 mo, n (%) | 0.08 | ||
| Yes | 81 (15.6%) | 11 (8.4%) | |
| No | 437 (84.0%) | 120 (91.6%) | |
| Unknown | 2 (0.4%) | 0 (0%) | |
| Fasting blood glucose (mg/dL), mean (range) | 133.95 (60–303) | 127.84 (79–209) | 0.32 |
| Surgeries before index operation (count), mean (range) | |||
| Ever | 0.58 (0–12) | 0.61 (0–14) | 0.39 |
| 90 d Prior | 0.07 (0–5) | 0.02 (0–1) | 0.13 |
| Direct cost of operative supplies and implants ($), mean (range) | 10,254 (116–50,894) | 6696 (342–27,592) | <0.001 |
| Length of hospital stay (h), mean (range) | 104.64 (24–1070) | 96.59 (26–563) | 0.006 |
| Length of follow-up (mo), mean (range) | 43.62 (0.5–83.11) | 38.24 (0.7–80.74) | 0.018 |
| Non-neurosurgical operations 30 d after index operation (count), mean (range) | 0.07 (0–3) | 0.09 (0–2) | 0.31 |
Note: Statistically significant (P < 0.05) values are bolded.