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

ObjectivesSurgeons 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.MethodsWe collected thirty sets of postoperative CT images from patients undergoing craniectomy. We measured the skull defect volume by computer-assisted volumetric analysis (Vm) and our own ABC technique (Vabc). We then compared the volumes measured by these two methods.ResultsThe Vm ranged from 3.2 to 76.4 mL, with a mean of 38.9 mL. The Vabc ranged from 3.8 to 71.5 mL, with a mean of 38.5 mL. The absolute differences between Vabc and Vm ranged from 0.05 to 17.5 mL (mean: 3.8 ± 4.2). There was no statistically significant difference between Vabc and Vm (p = 0.961). The correlation coefficient between Vabc and Vm 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.ConclusionWe 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.