How does bone thickness affect the split pattern of sagittal ramus osteotomy?

This study examined the influence of bone thickness on the split pattern of sagittal ramus osteotomy at 62 sites using Dolphin 3D software. Four measurements of thickness were obtained from the preoperative computed tomography scans: measurement A was made 1.5mm above the lingula, using the coronal and sagittal planes; measurement B was made at the same height as measurement A and 1mm from the anterior border of the ramus; measurement C was obtained 5mm distal to the last molar and 5mm below the upper border of the mandible; measurement D was made in the area between the first and second molars, 6mm above the mandibular border. Three-dimensional postoperative images were used to classify the split pattern into types, based on the classification of Plooij et al. The data were analyzed using the Kruskal-Wallis test, followed by Dunn post-hoc test. Thirty-five sagittal splits were type I, one was type II, 19 were type III, and seven were type IV. Type I presented the greatest thickness, whereas type IV presented the lowest. There was a statistically significant difference in thickness only for measurement A, when types I and IV were compared. The results indicate that thinner mandibular rami are more prone to bad splits.