As simultaneous mobilization of the maxilla and mandible has enhanced the success rates for correction of various dentofacial deformities in recent years, Le Fort I osteotomy is now routinely performed in many clinics. However, complications of life-threatening hemorrhage have been reported to be associated with Le Fort I osteotomy. It was stressed that hemorrhage is primarily related to damage of the internal maxillary artery.
The purpose of this investigation was to elucidate which osteotome (swan's neck osteo tome, modified swan's neck osteotome, Obwegeser osteotome, Kawamoto osteotome) is the safest to use to perform disjunction between the pterygoid plate and the maxillary tuberosity, and to determine the impact force required to effect this disjunction. Using human air-dried skulls, the impact force and dynamic strain of the disjunction of the pterygomaxillary suture were measured.
The following results were obtained:
1) The relationship between the absolute values of the impact force and dynamic strain were linear with all osteotomes.
2) The impact force was minimum with the Kawamoto osteotome.
3) The rate of normal disjunction was highest when the swan's neck osteotome was employed. With the Kawamoto osteotome normal disjunction was obtained at a high frequency at the first disjunction.
4) The disjunction lines running obliquely upwards on the pterygoid plate were observed most frequently in both the first and last disjunction series.
5) Using the swan's neck osteotome, we found large dynamic strains on the horizontal plate of the palatine in the first disjunction series and on the central part of the medial pterygoid plate in the last disjunction series.
6) Employing the modified swan's neck osteotome, we measured large dynamic strains on the central part of the lateral pterygoid plate and on the upper and central parts of the medial pterygoid plate.
7) With the Obwegeser osteotome, large dynamic strains were measured on the upper and central parts of the lateral and medial pterygoid plates.
8) With the Kawamoto osteotome, large dynamic strains were detected on the upper part of the medial pterygoid plate.
The results suggest the swan's neck or Kawamoto osteotome to be preferable for performing disjunction ebtween the pterygoid plate and the maxillary tuberosity. However, when empolying the Kawamoto osteotome in the last disjunction, it was necessary to firmly hold the movable maxilla.