Morphologic basis for the intraoral vertical ramus osteotomy: Anatomic and radiographic localization of the mandibular foramen

Purpose: The study goals were to provide anatomic and radiographic parameters that permit the performance of an intraoral vertical ramus osteotomy (RaO) without violation of the mandibular foramen (Frn) and to evaluate the usefulness of the LeVasseur-Merrill retractor (Walter Lorenz Surgical, Jacksonville, FL) developed for IVRO. Materials and Methods: Two hundred eighty dry adult human mandibular rami were measured, directly and via panoramic radiography, to obtain the horizontal and vertical positions of the Fm in the mandibular ramus. Measurements of the dry mandible were also compared with the radiographs to estimate Fm location. Results: The Fm is located approximately at the posterior third of the ramus, in both the vertical and horizontal directions. The Fm was located within 7 mm of the posterior edge of the mandible in only 3.3% of the rami. Radiographic distortion of the total length of the ramus was an average of only 0.9%. The LeVasseur-Merrill. retractor was effective in 98.9% of the analyzed rami. Conclusions: Estimation of the Fm position during surgery on the posterior edge of the ramus is useful. Measurement of the ramus width, performed with preoperative panoramic radiography, effectively locates the Fm. The LeVasseur-Merrill retractor, when correctly positioned, was an effective toot in determining the appropriate thickness of the WRO proximal fragment. (C) 2002 American Association of Oral and Maxillofacial Surgeons.