Hospital consolidation into health systems has mixed effects on surgical quality, potentially related to degree of surgical centralization at high-volume (hub) sites. We developed a novel measure of centralization and evaluated a hub and spoke framework. Surgical centralization within health systems was measured using hospital surgical volumes (American Hospital Association) and health system data (Agency for Healthcare Research and Quality). Hub and spoke hospitals were compared using mixed effects logistic regression and system characteristics associated with surgical centralization were identified using a linear model. Within 382 health systems containing 3022 hospitals, system hubs perform 63% of cases (IQR 40-84%). Hubs are larger, in metropolitan and urban areas, and more often academically affiliated. Degree of surgical centralization varies ten-fold. Larger, multistate, and investor-owned systems are less centralized. Adjusting for these factors, there is less centralization among teaching systems (p ​< ​0.001). A hub-spoke framework applies to most health systems but centralization varies significantly. Future studies of health system surgical care should assess the contributions of surgical centralization and teaching status on differential quality.