Tension forces in relation to LeFort III osteotomies.

Complications associated with LeFort III osteotomies have led to modifications of the procedure. Attempts to decrease morbidity include performing incomplete osteotomies or eliminating pterygomaxillary dysjunction. The purpose of this study was to determine the amount of tension required for separation of the midface from the pterygoid plates and to observe the fracture patterns. An Instron machine (Instron Corporation, Canton, MA) was used to measure the tension forces in 16 cadaver skulls divided into five groups. The groups varied as to whether the osteotomies were complete and whether pterygomaxillary separation was performed. Specimens with incomplete osteotomies and without pterygomaxillary separation required greater tension forces for separation and exhibited a high percentage (47%) of unfavorable fractures. Because high amounts of tension are required leading to unpredictable separations, we recommend complete osteotomies with pterygomaxillary dysjunction when performing LeFort III osteotomies.