Table 2.
Summary of pre-operative OKS, post-operative factors, and demographic confounding factors, in the pain free and chronic pain groups from the NJR-HES dataset.
| Parameter | Whole cohort |
No chronic pain |
Chronic pain |
|---|---|---|---|
| (n = 258,386) | (n = 214,684) | (n = 43,702) | |
| Preoperative OKS | 9.22 points (SD 4.64) | 9.76 points (SD 4.58) | 6.59 points (SD 4.02) |
| 0 to 4 | 42,331 (16.51%) | 27,411 (12.87%) | 14,920 (34.40%) |
| 5 to 7 | 56,918 (22.21%) | 44,483 (20.89%) | 12,435 (28.67%) |
| 8 to 9 | 40,513 (15.81%) | 34,197 (16.06%) | 6316 (14.56%) |
| 10 to 12 | 54,570 (21.29%) | 48,667 (22.85%) | 5903 (13.61%) |
| 13 to 28 | 61,990 (24.18%) | 58,198 (27.33%) | 3792 (8.74%) |
| Missing | 2064 (0.80%) | ||
|
Demographics | |||
| Age | |||
| <50 | 3398 (1.32%) | 2214 (1.03%) | 1184 (2.71%) |
| 50–59 | 26,977 (10.44%) | 19,792 (9.22%) | 7185 (16.44%) |
| 60–69 | 88,496 (34.25%) | 72,782 (33.90%) | 15,714 (35.96%) |
| 70–79 | 101,536 (39.30%) | 86,926 (40.49%) | 14,610 (33.43%) |
| 80–84 | 27,099 (10.49%) | 23,549 (10.97%) | 3550 (8.12%) |
| 85+ | 10,880 (4.21%) | 9421 (4.39%) | 1459 (3.34%) |
| Missing | 0 (0.00%) | ||
| Sex | |||
| Female | 146,510 (56.70%) | 120,758 (56.25%) | 25,752 (58.93%) |
| Male | 111,876 (43.30%) | 93,926 (43.75%) | 17,950 (41.07%) |
| Missing | 0 (0.00%) | ||
| BMI | |||
| Underweight | 231 (0.12%) | 194 (0.12%) | 37 (0.12%) |
| Normal | 17,000 (8.96%) | 14,948 (9.42%) | 2052 (6.58%) |
| Overweight | 64,509 (33.99%) | 56,098 (35.37%) | 8411 (26.99%) |
| Obese class 1 (30–34.9) | 62,736 (33.06%) | 52,243 (32.94%) | 10,493 (33.67%) |
| Obese class II (35–39.9) | 32,018 (16.87%) | 25,279 (15.94%) | 6739 (21.62%) |
| Obese class 3 (40+) | 13,289 (7.00%) | 9856 (6.21%) | 3433 (11.02%) |
| Missing | 68,603 (26.55%) | ||
| ASA grade | |||
| P1 - Fit and healthy | 23,717 (9.18%) | 20,534 (9.56%) | 3183 (7.28%) |
| P2 - Mild disease not incapacitating | 194,989 (75.46%) | 163,452 (76.14%) | 31,537 (72.16%) |
| P3 - Incapacitating systemic disease | 39,061 (15.12%) | 30,238 (14.08%) | 8823 (20.19%) |
| P4 – P5 - Life threatening disease/Expected to die within 24 h s | 619 (0.24%) | 460 (0.21%) | 159 (0.36%) |
| Missing | 0 (0.00%) | ||
| Index of Multiple Deprivation (IMD) quintiles | |||
| Most deprived | 34,653 (13.55%) | 25,171 (11.85%) | 9482 (21.89%) |
| 2 | 45,298 (17.71%) | 36,011 (16.95%) | 9287 (21.44%) |
| 3 | 57,301 (22.40%) | 48,094 (22.64%) | 9207 (21.26%) |
| 4 | 61,262 (23.95%) | 52,813 (24.86%) | 8449 (19.51%) |
| Least deprived | 57,251 (22.38%) | 50,360 (23.70%) | 6891 (15.91%) |
| Missing | 2621 (1.01%) | ||
| 3 month complications | |||
| Blood transfusion | 90 (0.03%) | 77 (0.04%) | 13 (0.03%) |
| Acute renal failure | 632 (0.24%) | 477 (0.22%) | 155 (0.35%) |
| Neurovascular injury | 22 (0.01%) | 17 (0.01%) | 5 (0.01%) |
| Mechanical complication of prosthesis | 1050 (0.41%) | 658 (0.31%) | 392 (0.90%) |
| Fracture | 37 (0.01%) | 27 (0.01%) | 10 (0.02%) |
| Surgical site infection | 1268 (0.49%) | 901 (0.42%) | 367 (0.84%) |
| Wound disruption | 646 (0.25%) | 475 (0.22%) | 171 (0.39%) |
| Urinary tract infection | 873 (0.34%) | 639 (0.30%) | 234 (0.54%) |
| DVT/PE | 786 (0.30%) | 602 (0.28%) | 184 (0.42%) |
| Acute MI | 271 (0.10%) | 229 (0.11%) | 42 (0.10%) |
| Respiratory tract infection | 1003 (0.39%) | 763 (0.36%) | 240 (0.55%) |
| Stroke | 180 (0.07%) | 144 (0.07%) | 36 (0.08%) |
| 3 month readmissions | 32,930 (12.74%) | 24,877 (11.59%) | 8053 (18.43%) |
| 3 month reoperations | 3848 (1.49%) | 2718 (1.27%) | 1130 (2.59%) |
| 3 month revision | 835 (0.32%) | 528 (100.00%) | 307 (0.70%) |
| Surgical complication 1 or greater | 1224 (0.47%) | 972 (0.45%) | 252 (0.58%) |
| Length of stay (continuous) | 4.58 days (SD 3.27) | 4.45 days (SD 3.19) | 5.19 days (SD 3.57) |
| <2 days | 3831 (1.48%) | 3226 (1.50%) | 605 (1.38%) |
| 2–4 days | 97,795 (37.85%) | 84,510 (39.37%) | 13,285 (30.40%) |
| 4–6 days | 99,385 (38.47%) | 82,978 (38.65%) | 16,407 (37.54%) |
| 6 plus days | 57,362 (22.20%) | 43,958 (20.48%) | 13,404 (30.67%) |
| Missing | 13 (0.01%) | ||