Relapse tendency after BSSO surgery differs between 2D and 3D measurements: A validation study

Bilateral sagittal split ramus osteotomy (BSSO) surgery is used to correct various dento-skeletal deformities. Clinical outcomes are critically dependent on accurate and proper positioning of skeletal units created by BSSO. Monitoring skeletal changes postoperatively is a major part of follow-up. Between January 2015 and December 2015, 24 patients underwent BSSO surgery without any other segmental osteotomy (mean age, 29.9 ± 14.2 [range, 17-67] years; 18 females). Cephalometric X-rays and cone-beam computed tomography scans were performed 6 weeks and 12 months postoperatively. We compared the position displacement at three mandibular points at both postoperative time points using 2- and 3-dimensional analysis separately and examined the relationship between these methods. Horizontally in at least in 14/24 patients, the difference between 2-dimensional and 3-dimensional measurements was >1 mm. Vertically in at least in 16/24 patients, the difference between 2-dimensional and 3-dimensional measurements was >1 mm. A scatter plot with orthogonal regression indicated the relationships between the 2-dimensional measurement and the corresponding 3-dimensional measurement in the horizontal and vertical directions. Skeletal relapse with 2-dimensional-measurements differed significantly from the 3-dimensional measurements. There was no evidence of a relationship between the two types of measurements regarding the direction and the location of the landmarks.