Estimating postoperative skull defect volume from CT images using the ABC method

Objectives: Surgeons often perform decompressive craniectomy to alleviate a medically-refractory increase of intracranial pressure. The frequency of this type of surgery is on the rise. The goal of this study is to develop a simple formula for clinicians to estimate the volume of the skull defect, based on postoperative computed tomography (CT) studies. Methods: We collected thirty sets of postoperative CT images from patients undergoing craniectomy. We measured the skull defect volume by computer-assisted volumetric analysis (V_m) and our own ABC technique (V_abc). We then compared the volumes measured by these two methods. Results: The V_m ranged from 3.2 to 76.4 mL, with a mean of 38.9 mL. The V_abc ranged from 3.8 to 71.5 mL, with a mean of 38.5 mL. The absolute differences between V _abc and V_m ranged from 0.05 to 17.5 mL (mean: 3.8 ± 4.2). There was no statistically significant difference between V_abc and V_m (p = 0.961). The correlation coefficient between V _abc and V_m was 0.969. In linear regression analysis, the slope was 1.00086 and the intercept was -0.0035 mL (r² = 0.939). The residual was 5.7 mL. Conclusion: We confirmed that the ABC technique is a simple and accurate method for estimating skull defect volume, and we recommend routine application of this formula for all decompressive craniectomies.