Surgeons identified as high-volume index adopters of robotic bariatric surgery were associated with lower robotic adoption among peer surgeons. The pattern was consistent with a crowding-out hypothesis, but the retrospective observational study cannot show that the high-volume surgeons caused colleagues to adopt less often.
Among 106 peer surgeons, 50, or 47.2%, adopted robotics. The median time to adoption was 1,730 days, with the middle half of adoption times ranging from 652 to 2,543 days.
What the researchers compared
The analysis drew on adults who underwent primary laparoscopic or robotic bariatric surgery in the Michigan Bariatric Surgery Collaborative between 2006 and 2025. The statewide quality improvement registry included 87,068 procedures performed by 121 surgeons at 41 hospitals.
For the peer-surgeon analysis, researchers defined peers as non-index surgeons at sites with robotic programs and assigned them to their earliest robotic site. They examined four index-adopter characteristics: high surgical volume, low complication rate, a fast learning curve and a composite quality indicator.
The primary outcome was whether a peer surgeon adopted robotic surgery. The main analysis used multivariable logistic regression, followed by sensitivity analyses using propensity-score matching, inverse-probability weighting and causal-forest methods.
The signal was consistent, with limits
High-volume index adopters were associated with lower peer adoption, with an adjusted odds ratio of 0.30. The 95% confidence interval ran from 0.09 to 0.84, and the reported P value was .03. An odds ratio compares estimated odds between groups, so a value below 1 points to lower estimated adoption odds in the high-volume group. The confidence interval shows that the size of the association remained uncertain.
The pattern also appeared in additional checks. An inverse-probability-weighting analysis, which reweights observations according to their estimated probability of receiving the exposure, produced an odds ratio of 0.37 with P = .04. A causal-forest analysis reported an average-treatment-effect estimate of -0.26 with P = .02. The direction of the high-volume finding was consistent across all seven analytical approaches, although statistical significance was reported in three. Confidence intervals for the inverse-weighting and causal-forest estimates were not supplied in the reviewed material.
A hypothesis, not a verdict
The authors interpret the link between high-volume index-adopter performance and lower peer adoption as consistent with crowding out. They suggest that the spread of robotic technology may require attention to equitable access to robotic resources, rather than relying on peer influence from high-performing early adopters.
The data do not identify the mechanism behind the association. Institutional resource constraints, limited robotic operating time or another factor could be involved, but the study did not establish which explanation fits the pattern.
Because this was retrospective registry evidence, it supports an association rather than a causal effect. The findings may not apply outside the participating statewide quality collaborative, adult bariatric surgery or the study period, and they do not show that changing an index adopter’s volume or reallocating robotic resources would increase peer adoption.
Data access and disclosures
The MBSC data were not publicly available because of data-governance agreements, although researchers could contact the MBSC Coordinating Center about collaborative access. The study was supported by a research agreement with the Michigan Bariatric Surgery Collaborative, whose support came from Blue Cross and Blue Shield of Michigan and Blue Care Network. The authors state that the funders had no role in the study or publication decisions.
The competing-interest statement reported honoraria from Blue Cross Blue Shield of Michigan for Oliver Varban and Arthur Carlin, and salary support from the organization for Jonathan Finks and Nabeel Obeid. The relationships concerned leadership and participation in the Michigan Bariatric Surgery Collaborative.
Paper data and sources
Original title: Association of Index Adopter Characteristics With Peer Surgeon Adoption of Robotic Bariatric Surgery.
Authors: Jayson Marwaha, Matthew Bucala, Akram Irshaid et al.
Journal/Repository: Obesity surgery
Status: Peer-reviewed
First online: 2026-08-21
DOI: 10.1007/s11695-026-08905-w
Original paper · Full text