TABLE 1.
Comparisons between SSI and non‐SSI group in terms of demographics, patient, injury surgery variables and the biomarkers measured at admission
| Variable | Non‐SSI group (n = 876) | SSI group (n = 24) | P value |
|---|---|---|---|
| Sex (male) | 812 (92.7) | 23 (95.8) | .558 |
| Age (years) | 41.9 ± 11.2 | 41.5 ± 8.7 | .863 |
| ≤45 | 518 (59.1) | 15 (62.5) | .740 |
| BMI (kg/m2) | 25.1 ± 3.5 | 26.8 ± 3.6 | .023 |
| ≥26.4 (vs <26.4) | 273 (31.2) | 15 (62.5) | .001 |
| ≥28.0 (vs <28.0) | 150 (17.1) | 8 (33.3) | .039 |
| Occupation | .857 | ||
| Office work | 109 (12.4) | 2 (7.7) | |
| Labouring | 448 (51.3) | 15 (62.5) | |
| Retirement | 67 (7.6) | 2 (7.7) | |
| Manual work | 150 (17.2) | 3 (12.5) | |
| Others | 102 (11.7) | 4 (15.4) | |
| Attainment of education (years) | .570 | ||
| Illiteracy | 57 (6.5) | 2 (8.3) | |
| <6 | 227 (25.9) | 9 (37.5) | |
| 6‐11.9 | 482 (55.0) | 11 (45.8) | |
| ≥12 | 110 (12.6) | 2 (8.3) | |
| Current smoking | 135 (15.4) | 8 (33.3) | .018 |
| Current drinking | 278 (31.7) | 9 (37.5) | .550 |
| Hypertension | 76 (8.7) | 3 (12.5) | .514 |
| Diabetes mellitus | 42 (4.8) | 2 (8.3) | .754 |
| Heart or cardiovascular disease | 23 (2.4) | 1 (4.2) | 1.000 |
| History of any surgery | 32 (3.7) | 2 (8.3) | .235 |
| Injury mechanism (high‐impact trauma) | 625 (71.3) | 21 (87.5) | .107 |
| Fracture types (Sanders grades) | .953 | ||
| II | 445 (50.8) | 14 (56.5) | |
| III | 288 (32.9) | 7 (30.4) | |
| IV | 143 (16.3) | 3 (13.0) | |
| Time from injury to operation (day) | 8.0 ± 4.6 | 8.0 ± 4.9 | .990 |
| <7 | 352 (40.2) | 10 (41.7) | .413 |
| 7‐10 | 337 (38.5) | 6 (25.0) | |
| 11‐14 | 128 (14.6) | 5 (20.8) | |
| >14 | 59 (6.7) | 3 (12.5) | |
| Length of hospital stay | 16.1 ± 8.5 | 24.1 ± 24.6 | .001 |
| Operative time | 126.7 ± 70.8 | 134.2 ± 79.2 | .610 |
| Intraoperative blood loss | 167.9 ± 186.9 | 172.6 ± 113.9 | .905 |
| Incision level | .023 | ||
| I | 845 (96.5) | 21 (87.5) | |
| II | 31 (3.5) | 3 (12.5) | |
| ASA grade | .089 | ||
| I | 153 (17.5) | 1 (4.2) | |
| II or greater | 723 (82.5) | 23 (95.8) | |
| Anaesthesia mode | .848 | ||
| Regional (epidural/spinal) | 679 (77.5) | 19 (79.2) | |
| General | 197 (22.5) | 5 (20.8) | |
| Surgical approach | .371 | ||
| Tarsal sinus approach | 256 (29.2) | 5 (20.8) | |
| Extended lateral approach | 620 (70.8) | 19 (79.2) | |
| Bone‐grafting | .454 | ||
| Yes | 72 (8.2) | 3 (12.5) | |
| No | 804 (91.8) | 21 (87.5) | |
| Drainage use | 353 (40.3) | 7 (29.2) | .272 |
| Allogeneic blood transfusion | 69 (7.9) | 4 (16.7) | .120 |
| TP (g/L) | 65.0 ± 6.1 | 67.8 ± 5.7 | .024 |
| <60 g/L | 165 (18.8) | 1 (4.2) | .068 |
| Albumin (g/L) | 41.2 ± 5.1 | 44.4 ± 2.9 | .002 |
| <35 g/L | 95 (10.8) | 0 | .171 |
| HCRP (mg/L) | 30 ± 33.6 | 26.2 ± 44.8 | .603 |
| >8 mg/L | 604 (68.9) | 13 (54.2) | .124 |
| LDH (U/L) | 235.7 ± 117.7 | 223.2 ± 53.3 | .605 |
| >250 U/L | 292 (33.3) | 10 (41.7) | .394 |
| Sodium concentration (mmol/L) | 139.0 ± 3.2 | 139.9 ± 2.5 | .167 |
| <135 mmol/L | 202 (23.1) | 1 (4.2) | .029 |
| FBG (mmol/L) | 5.8 ± 1.5 | 5.6 ± 1.2 | .663 |
| ≥6.1 mmol/L | 192 (21.9) | 6 (25.0) | .719 |
| WBC (×109/L) | 8.9 ± 2.6 | 10.1 ± 3.3 | .036 |
| >10 × 109/L | 331 (37.8) | 14 (58.3) | .041 |
| Neutrophil (109/L) | 6.5 ± 2.4 | 7.8 ± 3.3 | .011 |
| >6.3 × 109/L | 413 (47.1) | 15 (62.5) | .137 |
| Lymphocyte (×109/L) | 1.6 ± 0.6 | 1.5 ± 0.5 | .444 |
| <1.1 × 109/L | 162 (18.5) | 6 (25.0) | .420 |
| platelet (×109/L) | 228.3 ± 79.7 | 229.1 ± 62.3 | .960 |
| >300 × 109/L | 124 (14.2) | 5 (20.8) | .357 |
| NLR | 4.8 ± 3.1 | 6.0 ± 3.8 | .044 |
| <6.4 | 696 (79.5) | 14 (58.3) | .012 |
| ≥6.4 | 180 (20.5) | 10 (41.7) | |
| PLR | 160.5 ± 83.9 | 162.1 ± 48.2 | .927 |
| <150 | 518 (59.1) | 10 (41.7) | .086 |
| ≥150 | 358 (40.9) | 14 (58.3) | |
| RBC (×1012/L) | 4.2 ± 0.6 | 4.5 ± 0.5 | .089 |
| <Lower limit | 168 (19.2) | 2 (8.3) | .181 |
| Haemoglobin (g/L) | 134.5 ± 17.3 | 138.5 ± 14.4 | .256 |
| <Lower limit | 117 (13.4) | 2 (8.3) | .474 |
| HCT (percentage) | 39.7 ± 5.3 | 40.9 ± 4.1 | .280 |
| <Lower limit | 120 (13.7) | 4 (2.7) | .677 |
Note: Data presentation, mean ± SD (standard deviation) or number (percentage); BMI, body mass index; ASA, American Society of Anesthesiologists; TP, total protein; HCRP, hyper‐sensitive C‐reaction protein; HDH, lactate dehydrogenase; WBC, white blood cell; FBG, fasting blood glucose; NLR, neutrophil/lymphocyte ratio; PLR, platelet/lymphocyte ratio; RBC, red blood cell, reference range: female, 3.5 to 5.0 × 1012/L; male, 4.0 to 5.5 × 1012/L. Haemoglobin, reference range: Female, 110 to 150 g/L; male, 120 to 160 g/L. HCT, haematocrit, reference range: female, 35% to 45%; male, 40% to 50%.