Influence of operative time window and surgeon fatigue on the risk of unplanned reoperation after lumbar spine surgery

Objective To investigate the influence of operative time window and surgeon fatigue on the risk of unplanned reoperation within 30 days after lumbar spine surgery. Methods A single-center retrospective cohort study was performed. A total of 630 patients undergoing primary lumbar spine surgery between January 2022 and December 2024 were enrolled. According to the operation start time recorded by the Anesthesia Information Management System (AIMS), operations were divided into routine time window (08:00–18:59) and evening time window (19:00–23:59). Surgeon fatigue was defined as surgeons having been on duty for ≥ 8 h overnight, or having completed ≥ 5 operations on the same day starting from the 5th case. Patients were stratified into four groups based on operative time window and surgeon fatigue status: routine time window + non-fatigue group (392 cases), routine time window + fatigue group (81 cases), evening time window + non-fatigue group (94 cases), and evening time window + fatigue group (63 cases). Clinical and perioperative data were collected. Operative duration, intraoperative blood loss and the rate of unplanned reoperation were compared among groups. Multivariate logistic regression was used to identify independent risk factors, and the interaction effect between operative time window and surgeon fatigue was tested. Results In the non-fatigue state of surgeons, operative duration and blood loss slightly increased in evening operations compared with routine-time operations, without statistically significant differences ( P > 0.05). Under fatigue conditions, operative duration and blood loss were significantly higher than those in the corresponding non-fatigue groups regardless of daytime or evening surgery ( P < 0.05). The evening + fatigue group exhibited the longest operative duration and maximum blood loss, which were significantly higher than the other three groups ( P < 0.05). Overall, 15 patients (2.38%) underwent unplanned reoperation. The main causes included malposition of internal fixation in 7 cases (46.67%), nerve injury in 3 cases (20.00%), poor wound healing / surgical site infection in 3 cases (20.00%), and postoperative hematoma in 2 cases (13.33%). Using the routine + non-fatigue group as the reference, pairwise comparison demonstrated that the risk of reoperation was significantly elevated in the evening + fatigue group ( P < 0.05). Although higher reoperation risks were observed in the routine + fatigue group and evening + non-fatigue group, the differences were not statistically significant ( P = 0.15). Multivariate logistic regression revealed that surgeon fatigue (OR = 3.63, 95%CI 1.61–8.18, P = 0.002) and evening surgery (OR = 2.13, 95%CI 1.39–4.08, P = 0.037) were independent risk factors for unplanned reoperation. Interaction analysis indicated that evening surgery significantly amplified risks under fatigue status (adjusted OR = 1.82, P = 0.04), with a synergistic effect between the two factors ( P = 0.02). Conclusion Surgeon fatigue is the primary factor contributing to the elevated risk of unplanned reoperation after lumbar spine surgery. Although evening surgery acts as an independent risk factor, its major clinical implication lies in the notable synergistic effect with surgeon fatigue, which increases the risk of reoperation. Reasonable surgical scheduling to avoid evening operations performed by fatigued surgeons may reduce reoperation rates and improve surgical safety.