Dento-facial Changes following a Combination of Le Fort I with Horseshoe Osteotomy and a Bilateral Sagittal Split Ramus Osteotomy for Mandibular Prognathism

Abstract

This study compared dento-facial changes after two-jaw surgery with or without horseshoe osteotomy of the maxilla in mandibular protrusion patients with open bite or long face. Twenty adult patients who underwent orthognathic surgery to correct mandible protrusion were enrolled in this study. The subjects were divided into two groups based on surgical method: 10 who underwent bilateral sagittal split ramus osteotomy for the mandible and combination osteotomy by Le Fort I and horseshoe for the maxilla (HS-TJ group), and 10 who underwent bilateral sagittal split ramus osteotomy for the mandible and Le Fort I osteotomy for the maxilla (TJ group). Lateral cephalograms were used to analyze dento-facial changes at five stages (T0: first visit, T1: before surgery, T2: within 3 months after surgery, T3: beginning of retention, T4: more than 2 years after surgery). Statistical analysis was performed using two-way layout analysis of variance with Tukey correction. We considered p<0.05 to represent statistical significance.
The following results were obtained:
1. At T0, no significant difference in dento-facial patterns was observed between the two groups.
2. From T1 to T2, SNA angle, SNB angle and ANB angle were improved in both groups after surgery. Significant differences were observed in SNA, SNB, ANB and occlusal plane angle. However, significant differences were observed in mandibular plane angle only in the HS-TJ group. In the HS-TJ group significant differences were observed in all linear measurement items except the horizontal distance of U1. In the TJ group, significant differences were observed in all linear measurement items except the vertical distance of U1.
3. From T2 to T3 and from T3 to T4, no significant differences were observed between the two groups in respect of changes in all measurement items.
4. In two-way layout analysis of variance, a significant difference in ANS-Me was observed between the two groups in respect of the method of orthognathic surgery.
In the HS-TJ group, superior repositioning of the maxillary molar without anterior movement of the maxillary incisor, clockwise rotation of the occlusal plane and decrease in the lower facial height were observed. The postoperative stability of the HS-TJ group was found to be satisfactory. It is suggested that a combination osteotomy by Le Fort I and horseshoe for the maxilla is a useful technique for treating mandibular protrusion patients with open bite or long face.