Cause of early skeletal relapse after mandibular setback.

The present study was undertaken to examine the factors that might be responsible for the skeletal relapse occurring during the period of intermaxillary fixation after mandibular setback osteotomy. Fifteen patients, treated for absolute mandibular prognathism by modified sagittal split ramus osteotomy and fixation by skeletal suspension wiring, were evaluated cephalometrically by reference to the degree of postsurgical superior shift of the gonial region of the distal segment as a parameter of relapse since such a shift was evident despite the use of wiring. It was found that the degree of inadvertent anteroposterior rotation of the proximal segment at surgery, rather than the extent and pattern of surgical repositioning of the distal segment, was significantly correlated with the degree of shift. This result emphasizes the justification of preserving the proximal segment in its exact original anatomic site, in addition to the use of skeletal fixation, to ensure predictable stability after mandibular setback osteotomy.