Volumetric Analysis of Unilateral Alveolar Bone Defect Using Modified Subtraction in Older Chinese Patients

A large number of older patients (≥13 y old) with alveolar clefts missed the optimal alveolar bone grafting time period in China. This study aimed to determine the accuracy and repeatability of modified computer-aided engineering subtraction for volumetric measurement of these patients. In addition, the study aimed to determine whether the volume of defect is correlated with cleft type (cleft lip and alveolus, cleft lip and palate), cleft location, age, and sex. Preoperative computed tomography data from 100 patients of unilateral alveolar cleft patients without secondary alveolar bone grafting were measured using 2 methods. The maxillary resin model around the alveolar cleft was printed using the 3-dimensional (D) printing method, and the volume of the defect was measured using the drainage method. In the modified subtraction method, Mimics software was used to simulate fracture filling by layer drawing, and the defect volume was determined by subtracting the preoperative fracture template from the filled 3D skull template. The mean time taken to calculate an alveolar cleft defect volume by modified subtraction method was 3.2 minutes. The average defect volume measured using the 3D printing and modified subtraction methods were 1.58±0.41 and 1.55±0.42 cm 3 , respectively. Findings suggest that cleft location and age do not affect the defect volume of older patients with alveolar cleft, unlike cleft type and sex. The modified computer-aided subtraction method provides good accuracy, consistency, and reproducibility in measuring alveolar ridge defect volume. Moreover, this method is more efficient and cost-effective than the 3D-printed model method.