Balancing flexibility and robustness in operating room scheduling: the impact of resource constraints under uncertainty

Operating Room (OR) management is a critical factor in hospital efficiency, yet it remains highly sensitive to daily uncertainties such as surgical duration variability, emergency arrivals, and last-minute cancellations. This paper addresses the gap between theoretical optimisation and operational reality by proposing a robust rolling horizon framework applied to a high-volume hospital. We adopt a bi-objective perspective balancing operational performance with schedule stability by minimizing system nervousness. Our approach investigates the impact of structural constraints, specifically room clustering and limited surgeon parallelism, on schedule robustness. We compare five algorithmic strategies, ranging from highly flexible unconstrained models to cautious approaches combining strict spatial boundaries (restricting each surgeon to specific ORs) with proactive temporal buffers (inserting protective time slacks during surgeon changeovers). Validated through trace-driven simulations using real-world data, our results demonstrate a counterintuitive finding: structural restrictions, while often perceived as inefficiencies in deterministic settings, are a fundamental requirement for maintaining operational stability under uncertainty. Furthermore, we provide a set of specialised reactive operators capable of repairing schedules in real time, offering a practical decision-support tool for complex OR environments.