Bilateral sagittal split osteotomy versus distraction osteogenesis for mandibular advancements

The aim of this thesis was to compare the treatment modality of distraction osteogenesis (DO) with the gold standard for mandibular advancement surgery. In fact we compare distraction osteogenesis with the standard of care, which is a conventional bilateral sagittal split osteotomy as described by Trauner and Obwegeser in 1957 and later modified by Dalpont/Hunsuck. The hypothesis is that DO does not provide significant advantages over BSSO in advancements of the mandible. The primary outcome will focus on neurosensory disturbances of the inferior alveolar nerve and skeletal stability. Other patient factors such as infections, pain scores, will also be evaluated. Finally the costs of both treatment modalities will also be taken into account. In the first part of this thesis the results are described of a retrospective of a retrospective cohort study. Patients in these studies were operated between 2001 and 2004 in the Isala Clinics, in Zwolle, The Netherlands. In chapter 2 and 3 objective and subjective neurosensory disturbances of the inferior alveolar nerve will be presented. In chapters 4 and 5 short- and long-term skeletal stability will be discussed. Because in these first studies patients were not randomly assigned to either treatment some confounders of outcome were found.
To avoid selection bias and to balance known and unknown prognostic factors we decided to perform a randomized clinical trial (RCT). The results of this RCT are presented in three parts, first neurosensory disturbances are addressed in chapter 6, followed by skeletal stability in chapter 7, and finally patient discomfort, operating times, blood loss, costs and postoperative infections are evaluated in chapter 8.