Tension forces in relation to LeFort III osteotomies

Complications associated with LeFort III osteotomies have led to modificati ons of the procedure. Attempts to decrease morbidity include performing inc omplete osteotomies or eliminating pterygomaxillary dysjunction. The purpos e of this study was to determine the amount of tension required for separat ion of the midface from the pterygoid plates and to observe the fracture pa tterns. An Instron machine (Instron Corporation, Canton, MA) was used to me asure the tension forces in 16 cadaver skulls divided into five groups. The groups varied as to whether the osteotomies were complete and whether pter ygomaxillary separation was performed. Specimens with incomplete osteotomie s and without pterygomaxillary separation required greater tension forces f or separation and exhibited a high percentage (47%) of unfavorable fracture s. Because high amounts of tension are required leading to unpredictable se parations, we recommend complete osteotomies with pterygomaxillary dysjunct ion when performing LeFort III osteotomies.