Effect of neurosurgical residency programs on neurosurgical patient outcomes in a single health care system: a cohort study

BACKGROUND: The evidence on the benefits and drawbacks of involving neurosurgical residents in the care of patients who undergo neurosurgical procedures is heterogeneous. We assessed the effect of neurosurgical residency programs on the outcomes of such patients in a large single-payer public health care system. METHODS: Ten population-based cohorts of adult patients in Ontario who received neurosurgical care from 2013 to 2017 were identified on the basis of procedural codes, and the cohorts were followed in administrative health data sources. Patient outcomes by the status of the treating hospital (with or without a neurosurgical residency program) within each cohort were compared with models adjusted for a priori confounders and with adjusted multilevel models (MLMs) to also account for hospital-level factors. RESULTS: A total of 46 608 neurosurgical procedures were included. Operative time was 8%-30% longer in hospitals with neurosurgical residency programs in 9 out of 10 cohorts. Thirty-day mortality was lower in hospitals with neurosurgical residency programs for aneurysm repair (odds ratio [OR] 0.30, 95% confidence interval [CI] 0.20-0.44), cerebrospinal fluid shunting (OR 0.52, 95% CI 0.34-0.79), intracerebral hemorrhage evacuation (OR 0.66, 95% CI 0.52-0.84), and posterior lumbar decompression (OR 0.32, 95% CI 0.15-0.65) in adjusted models. The mortality rates remained significantly different only for aneurysm repair (OR 0.19, 95% CI 0.05-0.69) and cerebrospinal shunting (OR 0.42, 95% CI 0.21-0.85) in MLMs. Length of stay was mostly shorter in hospitals with neurosurgical residents, but this finding did not persist in MLMs. Thirty-day reoperation rates did not differ between hospital types in MLMs. For 30-day readmission rates, only extracerebral hematoma decompression was significant in MLMs (OR 1.41, 95% CI 1.07-1.87). CONCLUSION: Hospitals with neurosurgical residents had longer operative times with similar to better outcomes. Most, but not all, of the differences between hospitals with and without residency programs were explained by hospital-level variables rather than direct effects of residents.