Segmenting the mandible in an orthognathic procedure to reposition the tooth-bearing part is generally known as a bilateral sagittal split osteotomy (BSSO). Historically, different ways of splitting the mandible have been advocated. The Trauner and Obwegeser technique (1955), the Dal Pont modification (1961), and the Hunsuck modification (1968) are the best documented. Various approaches, splitting techniques, and instruments have been advocated to reduce complications over the years since Hugo Obwegeser reported the operation in 1955. Despite these improvements, the procedure remains technically challenging in some cases. Intraoperative complications include nerve injury, bleeding, and mechanical problems, such as irregular split patterns. An unfavourable and unanticipated pattern of the mandibular osteotomy fracture is generally referred to as a ‘bad split’. Incidences of 0.2% up to 14.6% per split site have been reported.

Bad splits may cause mechanical instability, a disturbance in bony union, and lead to bone sequestration with subsequent infection. In addition, it has been proposed that temporomandibular joint (TMJ) dysfunction and inferior alveolar nerve damage may arise due to excessive intraoperative manipulation in an attempt to reposition the fractured segments, and that subsequent difficulty in positioning the condyle in the glenoid fossa may increase the risk of relapse. In order to reduce the risk of postoperative functional deficits, fractured split segments are best fixated and reconsolidated. However, few restorative techniques to manage the situation have been described.

The aim of this article is to review unfavourable split pattern types reported in the literature, and to present appropriate salvage procedures to manage the different types of undesired fracture.