Ｌｅ　Ｆｏｒｔ　Ｉ型骨切り術のためのＣＴによる下行口蓋動脈の走行位置の解剖学的検討

The Le Fort I osteotomy is a common surgical procedure for the treatment of dentofacial deformities. Because this procedure includes osteotomy of the medial and lateral maxillary sinus wall, pterygomaxillary dysjunction and down-fracturing of the maxilla, it has significant risk of severe hemorrhaging from the descending palatine artery lying in the greater palatine canal.<BR>We investigated the position of the greater palatine canal to provide a clinical safety guideline that minimizes injury to the descending palatine artery during Le Fort I osteotomy in Japanese patients.<BR>Seventy-two Japanese patients with dentofacial deformities, 33 males and 39 females ranging from 16 to 42 years old (mean age 25.5 years old) were examined with computed tomography (CT) scans. The axial images 3 mm above the nasal floor were used for this analysis.<BR>Anatomical position of the greater palatine canal was localized by three measurements, anterior, posterior and lateral distance. The anterior distance was defined by the distance from the piriform rim to the greater palatine canal and the posterior distance from the pterygomaxillary fissure to the greater palatine canal. The lateral distance was defined as the distance from the lateral margin of the pterygomaxillary fissure to the lateral sinus wall.<BR>The average of the anterior distance was 36.67mm (range 32.69 to 42.66mm). There was a significant difference in the anterior distance between sexes. Based on the minimum anterior distance in this study, the safety guideline for Japanese patients for osteotomy of the medial sinus wall was assumed to be 30mm in Le Fort I osteotomy.<BR>The average of the posterior distance was 1.89mm (range 0 to 4.69mm). There was a negative significant correlation between age and posterior distance (γ=-0.23). Fifteen patients showed a distance of less than 1mm. It was assumed that these patients had a higher risk of injury to the descending palatine artery due to the narrow space between an osteotome and the greater palatine canal.<BR>The average of the lateral distance was 8.09mm (range 3.75 to 13.59mm). Fourteen patients showed a lateral distance of more than 10mm. The lateral distance is considered to be the length of bony contact between the posterior maxilla and the pterygoid plate that should be separated by an osteotome. The long bony contact increases the difficulty in pterygomaxillary dysjunction and the risk of untoward fracture leading to injury of the artery.