Relationship Between Mandibular Anatomy and the Occurrence of a Bad Split Upon Sagittal Split Osteotomy

Purpose: A bad split is a troublesome complication of the sagittal split osteotomy (SSO). The aim of this study was to evaluate the relation between the occurrence of a bad split and mandibular anatomy in SSO using cone-beam computed tomography. Materials and Methods: The authors designed a cohort retrospective study. Forty-eight patients (96 SSO sites) were studied. The buccolingual thickness of the retromandibular area (BLR), the buccolingual thickness of the ramus at the level of the lingula (BLTR), the height of the mandible from the alveolar crest to the inferior border of the mandible, (ACIB), the distance between the sigmoid notch and the inferior border of the mandible (SIBM), and the anteroposterior width of the ramus (APWR) were measured. The independent t test was applied to compare anatomic measurements between the group with and the group without bad splits. The receiver operating characteristic (ROC) test was used to find a cutoff point in anatomic size for various parts of the mandible related to the occurrence of bad splits. Results: The mean SIBM was 47.05 +/- 6.33 mm in group 1 (with bad splits) versus 40.66 +/- 2.44 mm in group 2 (without bad splits; P = .01). The mean BLTR was 5.74 +/- 1.11 mm in group 1 versus 3.19 +/- 0.55 mm in group 2 (P = .04). The mean BLR was 14.98 +/- 2.78 mm in group 1 versus 11.21 +/- 1.29 mm in group 2 (P = .001). No statistically significant difference was found for APWR and ACIB between the 2 groups. The ROC test showed cutoff points of 10.17 mm for BLR, 36.69 mm for SIBM, and 4.06 mm for BLTR. Conclusion: This study showed that certain mandibular anatomic differences can increase the risk of a bad split during SSO surgery. (C) 2014 American Association of Oral and Maxillofacial Surgeons