P69. ten-year institutional experience to predict calvarial bone flap loss using long-term outcomes

PURPOSE: Calvarial bone flap (CBF) loss is a common post-craniotomy complication associated with significant morbidities. Risk factors for CBF failure have not been well-defined. As CBF failure can occur many years following craniotomy, this study aims to determine risk factors of CBF loss using long-term follow-up data. METHODS: This retrospective study included patients who underwent craniotomy with CBF reinsertion between 2003-2013 at a tertiary academic institution. Patients were included if demographics, risk factors, and long-term outcomes were available. Multivariable logistic regression modeled the odds of CBF failure, defined as permanent removal. Median follow-up was 2.8 years (IQR 0.5-7.9). RESULTS: There were 222 patients who underwent craniotomy with CBF reinsertion, primarily for tumor resection or pressure relief. CBF failure occurred in 76 (34.2%) patients. Up to four CBF reinsertions were performed in both the failure and non-failure groups. The risks of CBF loss increased by each additional CBF elevation by 20-fold (p<0.001), each decade of age by 30% (p=0.043), and male sex by 3-fold (p=0.013) (C-index=0.93). CONCLUSION: This is the first study to definitively assess CBF loss using long-term follow-up in a contemporary cohort. Our regression model demonstrates that each CBF reinsertion dramatically increases risk of CBF loss. These results suggest that early multidisciplinary collaboration between plastic and neurological surgeons can improve patient selection and avoid the adverse sequela of high-risk calvarial reconstruction efforts.