[The position and course of mandibular canal through mandibular ramus in patients with prognathism].
PUEPOSE: To investigate the position and course of mandibular canal through mandibular ramus in patients with prognathism using computed tomography, and to relate the findings to sagittal split ramus osteotomy, and also to describe the anatomical variability of mandibular canal in order to reduce injuries to the inferior alveolar nerve.


METHODS
The mandibles of 45 patients with skeletal Class III prognathism undergoing sagittal split ramus osteotomy were examined by spiral computed tomography. The region from a plane containing the lowest point of mandibular foramen(base plane 0) to 25 mm below it was measured with 5 mm distance every plane. The following parameters were measured: total thickness of mandible through the center of mandibular canal, thickness of buccal and lingular cortical plate, and narrowest portion of bone marrow space between the outer mandibular canal and both the buccal and lingular cortex. All measurements were analyzed with SPSS 13.0 software package.


RESULTS
The thickness of mandible increased from the mandibular formen to mandibular body, there was no statistical difference among the sites with regards to the inner diameter of mandibular canal (F=1.044,P=0.391). The width of bone marrow space at the buccal side was significantly different between 3,4 plane and 0 plane,and the measured widths on the lingual side were significantly increased. The width of the buccal side bone marrow space at each site could be classified into three types, the separate type was most prevalent in this study(n=391 of 456,85.5%), contact and fusion type were 12.71% and 1.54% respectively. There was no significant difference between the left and right side.


CONCLUSIONS
On average, the mandibular canal is situated more lingually at all sites, and the width of bone marrow space at the buccal side is more narrow at 15-20mm below the mandibular foramen. When the width of marrow space at buccal side is absent, especially the fusion type, it is suggested to select an other procedure rather than sagittal split ramus osteotomy.
Ma
Jia
J
School of Stomatology, China Medical University, Shenyang, China.
Lu
Li
L
Song
Cong-Xiao
CX
D001853:Bone Marrow; D006801:Humans; D008334:Mandible / Q000033:anatomy & histology*; D008340:Mandibular Nerve; D059229:Osteotomy, Sagittal Split Ramus; D011378:Prognathism; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed