Strain distribution during separation of the pterygomaxillary suture by osteotomes. Comparison between Obwegeser's osteotome and swan's neck osteotome.

In the Le Fort I type osteotomy, separation of the pterygomaxillary suture is a dangerous manoeuvre which must be carried out during the surgical procedure. To determine the osteotome best suited for safe separation of the pterygomaxillary suture, we measured the strain distribution over the surrounding bone structures during the osteotomy, employing two types of osteotomes. In both the Obwegeser osteotome group and swan's neck osteotome group, a large strain was measured at the medial pterygoid plate on the side of osteotome application. The intensity of the strain at the medial pterygoid plate was higher in the Obwegeser osteotome group than in the swan's neck group. With the Obwegeser osteotome which is routinely and commonly used in orthognathic surgery, safe separation of the suture cannot be accomplished unless the blade is correctly applied to the suture and superoposterior compression of the pterygoid process is avoided.