Risk factors for breakage of biodegradable plate systems after bilateral sagittal split mandibular setback surgery

The aim of this retrospective study was to evaluate the risk factors associated with breakage of biodegradable plate systems after bilateral sagittal split mandibular setback. We studied 169 Japanese adults (62 men, 107 women; age range 16-53 years) with deformities of the jaw diagnosed as mandibular prognathism. All patients were treated by bilateral sagittal split osteotomy (BSSO) with 2 biodegradable fixation plates and screws at the anterior mandibular ramus. We collected the following data from the medical records and radiological findings: sex; age; degree of setback; presence of asymmetry; presence of open bite; operation; design of the plate; operating time; and blood loss. Multiple logistic regression analysis was used to find the factors that were independently associated with the dependent variable: breakage of the biodegradable plate system. In 10 of the 169 patients (6%) the biodegradable plate system for the BSSO broke. Factors that influenced whether or not the biodegradable plate system fractured were if they were asymmetrical (odds ratio (OR) 5.35; P=0.02) and had an open bite (OR 5.20; P=0.02). Asymmetry or open bite was significantly associated with breaks in the biodegradable plate system. Biodegradable plates should be used only when loading is minimal.