Stabilisation of sagittal split advancement osteotomies with miniplates: a prospective, multicentre study with two-year follow-up. Part II. Radiographic parameters.

This prospective study implied a two-year follow-up on a group of patients that underwent a Bilateral Sagittal Split Osteotomy (BSSO) for advancement (n=222) of the mandible that were treated in seven institutions following the same treatment protocol. The aim of Part II of this study was to correlate the clinical findings on stability and relapse as reported in Part I (clinical parameters) of this series of articles with the cephalometric findings. The mean skeletal relapse at pogonion of the whole group after two years was 0.9 mm. The clinically stable group, however, had only 0.4 mm relapse, whereas the clinical relapse group showed a mean relapse of 3.3 mm. The findings underline a relationship between the amount of advancement and relapse. The tendency for both, horizontal and vertical movement is the same, i.e., the larger the surgery effect, the larger the relapse. The angle post plane/mandibular plane showed the highest explained variance 9%. Patients with a high mandibular plane angle may be more prone to relapse. The explained variance of all considered prognostic factors together, however, is small (13%). The findings of this study express that patients with a clinical stable occlusion after a BSSO advancement, stabilised with miniplates, have a minimal to no skeletal relapse as measured on the cephalometric radiograms. The clinically non-stable group, however, appeared to have considerable skeletal relapse.