Background: Calvarial bone flap (CBF) loss is a common complication following craniotomy and subsequent skull reconstruction can be challenging. Defining predictors of CBF failure not only improves patient outcomes but reduces the need for complex reconstruction often requiring plastic surgery consultation. As CBF failure can occur many years following craniotomy, this study aimed to determine risk factors of CBF loss using long-term follow-up. Materials and Methods: This retrospective study included patients who underwent craniotomy with CBF reinsertion between 2003 and 2013 at a tertiary academic institution. Patients were included if demographics, comorbidities, and long-term outcomes were available. Multivariable logistic regression modeled the odds of CBF failure, defined as permanent removal for bone flap-related issues. The median follow-up was 6.9 years (interquartile range: 1.8-10.8 y). Results: There were 222 patients who met inclusion criteria and underwent craniotomy with CBF reinsertion, primarily for tumor resection or intracranial pressure relief. CBF failure occurred in 76 (34.2%) patients. Up to 4 CBF reinsertions were performed in both failure and nonfailure groups. The risks of CBF loss increased with each additional CBF elevation by 17-fold (P < 0.001), male sex by 3-fold (P = 0.005), and tumor etiology by 3-fold (P = 0.033) (C-index = 0.942). Conclusions: Each CBF reinsertion dramatically increases the risk of CBF loss. This finding may optimize patient selection and surgical planning. Early multidisciplinary discussions between plastic surgeons and neurosurgeons may avoid multiple CBF elevations and prevent the adverse sequela of high-risk calvarial reconstruction efforts.

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