Thirty-day Outcomes for Posterior Fossa Decompression in Adults with Chiari Type I Malformation: A Frailty-driven Perspective from the US National Surgical Quality Improvement Program

Introduction: When indicated, symptomatic Chiari 1 malformation (CM) patients may undergo suboccipital decompression surgery. Although this procedure is typically well-tolerated, pre-operative risk assessment and patient selection are critical. The objectives of the present study were twofold: 1) describe 30-day outcomes after suboccipital decompression (SOD) for CM with attention to preoperative frailty and 2) design a predictive model for the primary endpoint of non-home discharge disposition (NHD).

Methods: Patient cases (N=1015) were selected from the 2011-2020 American College of Surgeons – National Surgical Quality Improvement Program (NSQIP) database using diagnostic and procedural codes. Descriptive statistics were used to analyze total cohort baseline demographics, preoperative comorbidities, and postoperative outcomes. Univariate crosstabulation was used to compare baseline demographics and preoperative characteristics across the NHD and non-NHD subgroups. Receiver operator characteristic (ROC) curve analysis was used to assess the discriminative ability of the Risk Analysis Index (RAI) on NHD.

Results: The study cohort had a median age of 36 years and consisted of 80.6% female patients. The most common preoperative comorbidities were smoker status (24.4%), hypertension (19.2%), and diabetes mellitus (4.7%). The primary outcome, non-home discharge (NHD), occurred in 4.6% of the cohort cases (N=47). The most common other postoperative complications included superficial SSI (1.4%), organ space SSI (1.5%), Clavien-Dindo grade IV (CDIV; "life threatening") (1.5%), return to operating room (5.8%), unplanned readmission (9.3%), unplanned reoperation (5.3%), and reoperation for CSF leak (1.1%). ROC curve analysis demonstrated that RAI predicted NHD with significant discriminatory accuracy among adult Chiari I surgery patients (C-statistic: 0.731, 95% CI 0.648-0.814).

Conclusion : This decade-long analysis of a multi-center surgical registry provides nationally representative, modern, rates of 30-day outcomes after suboccipital decompression (SOD) for adult CM. Preoperative frailty assessment with the RAI may help identify higher-risk surgical candidates and may be used to reliably predict non-home discharge disposition.