Baseline characteristics of included patients by study group.
| Characteristic | Conventional (n = 24) | BESS (n = 22) | Total (N = 46) | P |
| Age, y, mean ± SD | 60.2 ± 12.8 | 63.0 ± 10.2 | 61.5 ± 11.6 | 0.405 |
| Sex, man, n (%) | 15 (62.5) | 12 (54.5) | 27 (58.7) | 0.804 |
| BMI, mean ± SD | 25.3 ± 3.5 | 25.6 ± 2.8 | 25.5 ± 3.1 | 0.765 |
| Diagnosis, n (%) | 0.725 | |||
| HIVD | 13 (54.2) | 14 (63.6) | 27 (58.7) | |
| Stenosis | 11 (45.8) | 8 (36.4) | 19 (41.3) | |
| Operation level, n (%) | 0.156 | |||
| L2–L3 | 0 (0.0) | 1 (4.5) | 1 (2.2) | |
| L3–L4 | 4 (16.7) | 1 (4.5) | 5 (10.9) | |
| L4–L5 | 18 (75.0) | 14 (63.6) | 32 (69.6) | |
| L5–S1 | 2 (8.3) | 6 (27.3) | 8 (17.4) | |
| Drainage, cc, mean ± SD | 38.8 ± 31.5 | 53.2 ± 24.4 | 45.5 ± 29.0 | 0.096 |
| Drain removal date, d, n (%) | 0.569 | |||
| 0 | 1 (4.2) | 0 (0.0) | 1 (2.2) | |
| 1 | 5 (20.8) | 6 (28.6) | 11 (24.4) | |
| 2 | 16 (66.7) | 15 (71.4) | 31 (68.9) | |
| 3 | 1 (4.2) | 0 (0.0) | 1 (2.2) | |
| 4 | 1 (4.2) | 0 (0.0) | 1 (2.2) | |
| Drain removal date, mean ± SD | 1.8 ± 0.8 | 1.7 ± 0.5 | 1.8 ± 0.6 | 0.525 |
| Neurological deficit, n (%) | 1 (4.2) | 0 (0.0) | 1 (2.2) | >0.99 |
| Comorbidity, n (%) | ||||
| Hypertension | 8 (33.3) | 8 (38.1) | 16 (35.6) | 0.983 |
| Diabetes mellitus | 2 (8.3) | 1 (4.8) | 3 (6.7) | >0.99 |
| ODI | ||||
| Preoperative | 0.19 ± 0.10 | 0.23 ± 0.09 | 0.21 ± 0.10 | 0.174 |
| Postoperative 3 mo | 0.07 ± 0.06 | 0.05 ± 0.04 | 0.06 ± 0.05 | 0.324 |
| Postoperative 6 mo | 0.05 ± 0.08 | 0.05 ± 0.07 | 0.05 ± 0.07 | 0.955 |
| Postoperative 12 mo | 0.03 ± 0.07 | 0.02 ± 0.05 | 0.02 ± 0.06 | 0.711 |
| Back pain VAS | ||||
| Preoperative | 4.88 ± 2.61 | 4.24 ± 2.45 | 4.58 ± 2.53 | 0.405 |
| Postoperative 3 mo | 1.78 ± 1.17 | 1.52 ± 1.29 | 1.66 ± 1.22 | 0.488 |
| Postoperative 6 mo | 1.35 ± 1.70 | 1.38 ± 1.56 | 1.36 ± 1.62 | 0.947 |
| Postoperative 12 mo | 0.61 ± 1.53 | 0.33 ± 0.80 | 0.48 ± 1.23 | 0.454 |
| Leg pain VAS | ||||
| Preoperative | 6.17 ± 2.30 | 6.36 ± 2.34 | 6.26 ± 2.29 | 0.775 |
| Postoperative 3 mo | 1.50 ± 1.29 | 1.32 ± 0.99 | 1.41 ± 1.15 | 0.597 |
| Postoperative 6 mo | 1.00 ± 1.22 | 1.45 ± 1.99 | 1.22 ± 1.63 | 0.362 |
| Postoperative 12 mo | 0.79 ± 1.93 | 0.32 ± 0.65 | 0.57 ± 1.47 | 0.267 |
Abbreviations: BESS, biportal endoscopic spine surgery; BMI, body mass index; HIVD, herniated intervertebral disc; ODI, Oswestry Disability Index; VAS, visual analog scale.