Volume Concentrates Reliably at Receiving Centres; the Skill-Mix and Quality Consequences Are Still Inferred

Question: How has regionalization of surgical services in Canada and other high-income countries affected the volume and skill mix of surgeons at receiving centres, and what unintended consequences for care quality have been documented?

Answer

Across these papers, the only consistently documented effect of regionalization is a large increase in case volume at receiving centres; the effect on surgeon skill mix is inferred rather than measured, and the inference generally runs toward dilution rather than upgrading. The clearest Canadian evidence comes from a single-institution analysis of Cancer Care Ontario's lung cancer surgery regionalization, which attributes a rise in thoracic transfusion to an influx of less-skilled thoracic surgeons and the closure of thoracic units at smaller hospitals rather than to case-mix change [2]. Documented unintended consequences are predominantly access-side — travel burden, EMS diversion, and rural patients not receiving intervention at all — while quality effects at receiving centres themselves are contested and rest on weak designs. Taken together, the retrieved literature supports the concentration-of-volume claim but does not support confident claims about the skill mix that concentration produces, because no study in this set measures surgeon-level volumes or credentials before and after a regionalization event.

Volume concentration at receiving centres is the best-documented and largest effect

Regionalization has redistributed case volume toward large urban teaching centres at scale: aortic dissection management at urban-teaching hospitals rose from 72% to 92% of United States hospitalizations between 2000 and 2021 [6]. At the receiving institution in the Ontario thoracic example, the opening of a new cancer care centre coincided with a significant increase in average transfusions among thoracic surgeons while control specialties showed no parallel change, consistent with a step-up in absorbed volume [2]. Concentration also operates by reorganizing referral pathways rather than by closing sites: consolidation of revision arthroplasty into specialist centres is described as mandating the formation of regional revision networks with standardized referral data from originating centres [8]. The receiving-centre workload question is therefore not whether volume rises but whether it rises faster than local capacity can accommodate.

The skill-mix change at receiving centres is inferred from outcomes, and the inference is dilution

The strongest available statement about skill mix is the argument that increased transfusions at The Ottawa Hospital were driven by less-skilled thoracic surgeons arriving with regionalization and by the closure of thoracic units at smaller hospitals [2]. The mirror-image scenario is quantified for Mohs micrographic surgery in the United States: residency/practice-trained surgeons constituted 45.3% of the 2024 workforce, supplied 52.1% of nonmetropolitan volume, and were the only Mohs surgeons in 223 counties, while simulated exclusion of this group would push 15.6 million more people beyond 60 minutes' drive and require roughly 21 years of fellowship pipeline to replace rural capacity [11]. That paper also shows the receiving-centre absorption limit: displaced volume of 353,736 Medicare cases per year would require surviving surgeons to raise volume 45.5%, and even with every survivor taking 20% more cases, 211,848 cases per year would have no slot [11]. Where regionalization takes the form of high-volume low-complexity hubs, the skill mix is deliberately narrowed to what those sites can support, since hubs and ambulatory surgery centres often lack higher-level care such as intensive care and are suited only to less comorbid patients [14].

Throughput gains at concentrated sites are real but conditional on how separation is implemented

Causal estimates from the staggered rollout of NHS England's surgical hub programme show hub adoption increased cost-weighted elective output per salary-weighted physician input by 14.5% and reduced average waiting times by 10 days (7.6%) [15]. Those gains are not generic to regionalization: standalone hubs on elective-only sites achieved larger productivity gains than integrated hubs inside acute hospital sites, and operating multiple hubs yielded gains more than double the overall average while a single hub showed no statistically significant effect [15]. Baseline surgical capacity is highly variable to begin with — median annual operating time across 14 specialties was 451 hours and 414 cases, with a tenfold range from cardiothoracic surgery to podiatry — so the headroom available for redistributed volume differs sharply by specialty and site [9].

The documented unintended consequences are access-side and fall on rural and remote patients

Centralization is characterized as delaying access and increasing carbon emissions, with cataract patients travelling a median 55.45 km and decentralization modelled to cut travel emissions by 34–40% [1]. In Ontario, 15.4% of long-term care residents need hospital destination decisions because their nearest emergency department lacks orthopaedic services, facing a median 2.7 km to that department versus 36.0 km to the nearest orthopaedic centre, and selective transfer protocols increase travel for false-positive patients with the greatest negative consequences concentrated in the 1.3% living more than 100 km from an orthopaedic centre [13]. The rural effect extends to treatment itself: since 2016, urban-teaching hospitals intervened on aortic dissections far more often than rural counterparts (21% versus 6%) [6]. Analogous dynamics appear outside surgery, where faster-trained emergency physicians in Ontario became more geographically concentrated around urban academic centres between 2015 and 2024, and relying on less extensively trained providers to plug staffing gaps may not improve equitable access [4].

Quality signals at receiving centres are ambiguous and vulnerable to measurement artefact

Within a single regional network, high-volume aortic centres achieved 3-year survival of 81.5% versus 66.7% at low-volume centres despite no significant difference in preoperative characteristics, with high-volume status independently associated with survival after adjustment [7] — evidence that concentration can help, but also that low-volume sites persist inside networks rather than disappearing. Measured case complexity at receiving centres is itself manipulable: structured surgeon chart review across a four-hospital academic system raised surgical case mix index from 2.68 to 2.97 with unchanged length of stay and an estimated $3,912 revenue increase per patient, showing that apparent complexity gains can reflect documentation rather than patient mix [5]. Against the dilution hypothesis, a nationwide Japanese survey found no regional disparity between urban and regional training sites in number of experienced surgeries, publications, off-the-job training, or satisfaction with training, with regional residents reporting higher income [3].

Conflicts and gaps

The central conflict is direct: the Ottawa analysis attributes a quality deterioration at a receiving centre to an influx of less-skilled surgeons [2], while the volume–outcome literature shows concentration at high-volume centres is associated with better survival [7]. These are reconcilable — volume may rise while average operator skill within the merged service falls — but the Ottawa study cannot test this, because it uses aggregate data scraped from a prior publication, estimates effects on log mean transfusions with other specialties as controls, and cannot separate surgeon composition from case-mix or blood-management practice change [2]. The broader evidence base is missing precisely the outcomes that matter here: a scoping review of rural hospital closures and mergers found knowledge gaps in financial, workforce, and utilization outcomes, reported that little is known about impacts on neighbouring hospitals and communities, and found no studies examining merger impacts on patients [10]. No retrieved paper measures surgeon-level case volume or credentialing at receiving centres before and after a regionalization event, and no Canadian study links regionalization to patient outcomes beyond the single-hospital transfusion analysis. Access findings are modelled rather than observed — emission reductions are projections from a k-means site-optimization model [1], and travel consequences are geospatial simulations rather than measured care delays [13]. Peripheral workforce supply is also not a fixed constraint: Canadian tax-deferral policy allowing physician incorporation reduced physician supply by 6.8% over the long run, with especially large declines among older physicians and high-earning surgical specialists, which alters any projection of how much volume receiving centres can absorb [12].

What would change the answer

The decisive study is a surgeon-identified, population-level difference-in-differences analysis around staggered regionalization events — for example Ontario's Cancer Care Ontario thoracic and hepatopancreatobiliary consolidations — measuring each receiving-centre surgeon's annual case volume, case mix, subspecialty credentialing, and risk-adjusted transfusion, reoperation, and margin outcomes, with sending-site surgeons tracked as they relocate or exit. Registry outcomes linked to surgeon identifiers, rather than hospital-level aggregate means, would resolve whether the Ottawa transfusion signal is compositional or practice-driven [2]. Applying the staggered-rollout design used for NHS surgical hubs to Canadian regionalization would separate implementation design (standalone versus integrated, single versus multiple receiving sites) from the effect of concentration itself [15]. Extending drive-time accessibility models to patient-level outcomes — travel time linked to stage at surgery, time-to-treatment, and postoperative mortality [13] [1] — would test whether access loss translates into measurable harm rather than inconvenience. Finally, prospective capacity simulations calibrated to observed operative hours [9] and to observed per-surgeon displacement limits [11] would establish, before implementation rather than after, at what point a receiving centre's skill mix becomes thin enough to erode the volume–outcome benefit it was built to capture.

References

[1] Hyman, G. Y., Reddy, R., Wurdeman, T., Crew, R. P., Shrime, M. G.. "Barriers to surgical care delivery are harming our planet: a case for decentralized provider services". medRxiv. 2026-07-02T00:00:00.000Z. URL: https://doi.org/10.64898/2026.06.30.26354345

[2] Smith, J., Smith, B., Pittman, T.. "The Effect of Regionalization of Thoracic Surgery on Blood Transfusion at the Ottawa Hospital". medRxiv. 2026-10-19T00:00:00.000Z. URL: https://doi.org/10.64898/2026.10.15.26365639

[3] Watanabe, G., Watanabe, J., Hayashi, S., Konishi, T., Poudel, S., Kiyasu, Y., Fukumoto, M., Korai, T., Nomura, S., Yamamoto, N., Nakajima, M., Hosoya, K., Saito, M.. "Regional disparity in surgical residency training and work environment between urban and regional hospitals: an additional perspective from a nationwide survey for surgical residents". medRxiv. 2024-12-11T00:00:00.000Z. URL: https://doi.org/10.1101/2024.12.11.24318834

[4] Kanter-Eivin, D., Armstrong, C., Esleben, A., Sweeny, G., Dowling, M., El Galad, A., Strobel, S.. "Do Faster-Trained Physicians Fill the Gaps? Geographic Concentration of Emergency Medicine physicians with different postgraduate training in Ontario Canada". medRxiv. 2025-04-30T00:00:00.000Z. URL: https://doi.org/10.1101/2025.04.29.25326528

[5] Kamine, T. H., Townsend, J., Fakhry, S. M., Jabbour, N., Kelly, E.. "Increase in Surgical Case Mix Index Across a Multi-Hospital System with Structured Limited Surgeon Chart Review". medRxiv. 2026-10-14T00:00:00.000Z. URL: https://doi.org/10.64898/2026.10.13.26365430

[6] Conroy, P. D., Tolaymat, B., Schubert, A., Tjaden, B., Minakata, K., Batista, P., Schermerhorn, M. L., Lombardi, J. V.. "Impact of Centralized Care at Aortic Centers on Aortic Dissection Outcomes: A 20-Year Analysis of U.S. Hospitals". medRxiv. 2025-05-16T00:00:00.000Z. URL: https://doi.org/10.1101/2025.05.14.25327652

[7] Meknat, A., Pettit, A. N., Cho, P., Hollingsworth, N., Taylor, W., Halbreiner, M. S.. "Type A Aortic Dissection Repair at High Versus Low Volume Centers". medRxiv. 2025-05-05T00:00:00.000Z. URL: https://doi.org/10.1101/2025.05.02.25326910

[8] Shelton, J., Dorman, S.. "Minimum required data for decision at a revision MDT in an arthroplasty network: a structured protocol for a systematic review of the literature and consensus statement using a two round Delphi process.". medRxiv. 2025-10-15T00:00:00.000Z. URL: https://doi.org/10.1101/2025.10.14.25337994

[9] Andrade, N. S.. "How Much Time Do Surgeons Spend Operating?". medRxiv. 2025-02-18T00:00:00.000Z. URL: https://doi.org/10.1101/2025.02.15.25321677

[10] Coates, A., Probst, J., Sarwal, K., Riaz, S., Grudniewicz, A.. "The Impact of Rural Hospital Closures and Mergers on Health System Ecologies: A Scoping Review". medRxiv. 2025-02-02T00:00:00.000Z. URL: https://doi.org/10.1101/2025.01.31.25321470

[11] Jeon, H., Logue, M. E., Murakawa, G., Yu, K. K.. "Access Consequences of Restricting Mohs Micrographic Surgery to Fellowship-Trained Surgeons: A National Workforce, Board-Certification, and Drive-Time Simulation Study". medRxiv. 2026-09-14T00:00:00.000Z. URL: https://doi.org/10.64898/2026.09.12.26362922

[12] Strobel, S., Kanter-Eivin, D., Son, H., Steiner, A.. "The Effects of Allowing Professional Incorporation on Physician Labour Supply". medRxiv. 2025-08-18T00:00:00.000Z. URL: https://doi.org/10.1101/2025.03.14.25323936

[13] Yee, N. J., Chen, T., Huang, Y. Q., Whyne, C., Halai, M.. "Trade-offs in emergency transport protocols for access to hip fracture management: a geospatial analysis of selective versus standard transfer in Ontario long-term care". medRxiv. 2026-04-14T00:00:00.000Z. URL: https://doi.org/10.64898/2026.04.12.26350713

[14] Woodward, C., Green, J., Reed, M., Beard, D., Williams, P.. "Risk stratification in hip and knee replacement using Artificial Intelligence: a dual centre study to support the utility of high-volume low-complexity hubs and ambulatory surgery centres.". medRxiv. 2024-12-06T00:00:00.000Z. URL: https://doi.org/10.1101/2024.11.29.24317637

[15] Zecharias Anteneh, Adriana Castelli, Peter Sivey, Andrew Street, Jinglin Wen, Joy Adamson. "High Volume Low Complexity Surgical Hubs in England: Can They Improve Physician Productivity?". arxiv. 2026-09-10T00:00:00.000Z. URL: https://arxiv.org/abs/2609.1038

How this survey was made

This survey answers one question: “How has regionalization of surgical services in Canada and other high-income countries affected the volume and skill mix of surgeons at receiving centres, and what unintended consequences for care quality have been documented?”

We keep our own collection of recent preprints and refresh it every day from bioRxiv, medRxiv, arXiv, PsyArXiv, SocArXiv and ChemRxiv. For each survey, we search that collection for recent work and keep the strongest matches: papers that use the same terms as the question, and papers on the same topic in different words.

The text was written from the titles and abstracts of those papers; the full texts were not read. Statements that draw on a particular paper are marked with a number in brackets. The reference list just above is the 15 papers whose work this text draws on, chosen from the 72 papers those searches returned; the rest of the shortlist is not printed. It is not a complete review of everything published on the question.

Treat this as a starting point and a reading list, not a peer-reviewed review. The searches behind this survey ran on October 22, 2026 and covered work from the previous two years.