To Örebro University

INTRODUCTION: Chronic subdural hematoma (cSDH) frequently recurs. Numerous studies have investigated the influence of various factors on the likelihood of recurrence, yet the potential influence of individual surgeon identity beyond general experience level remains unclear. RESEARCH QUESTION: To evaluate whether surgeon-specific differences contribute to recurrence rates whilst accounting for standardized technique and known patient-/procedure-related factors.

MATERIALS AND METHODS: Retrospective analysis of burr hole evacuation for cSDH or hygroma at a single tertiary center. Standardized surgical technique involved two burr holes with subdural lavage and drainage placement. Primary outcome was symptomatic recurrence necessitating redo surgery. Surgeon-specific variability in recurrence was assessed via three statistical methods: risk-standardized observed-to-expected (O/E) ratios, logistic generalized estimating equations (GEE), and hierarchical Bayesian logistic modeling, adjusted for covariates.

RESULTS: Among 116 patients (age = 78.0 years, 75.0 % = male, 26.7 % = bilateral procedures), symptomatic recurrence occurred in 15 cases (12.9 %). Risk-standardized-O/E recurrence ratios varied from 0.00 to 1.65, with wide confidence intervals indicating uncertainty, but all within expected ranges (median O/E = 1.11, IQR = 0.60-1.45). GEE analysis demonstrated significant surgeon-specific clustering (ICC = 0.61, large effect), indicating between-surgeon differences could explain more than half of the remaining variance in recurrence. Bayesian hierarchical modeling showed moderate surgeon-specific clustering with an ICC = 0.14, indicating that between-surgeon differences accounted for approximately 14 % of total variance in recurrence.

DISCUSSION AND CONCLUSIONS: Our study demonstrates modest yet measurable surgeon-specific differences in recurrence rates following standardized burr-hole evacuation for cSDH. These findings support further investigation into surgeon-specific variability, particularly for more complex procedures, to identify actionable technical differences and optimize surgical outcomes universally.