Intraoral vertical ramus osteotomy (IVRO) is used widely to correct mandibular prognathism. However, several disadvantages of this procedure have been reported, such as condylar luxation and bony interference at the osteotomy site. The aim of this study was to survey the incidence of complications (condylar luxation and bony interference) based on the shape of the osteotomy line. One hundred and eighty-five rami in 118 patients with jaw deformities, which were treated with IVRO, were examined retrospectively. The shape of the osteotomy line and the postoperative complications were examined on panoramic radiographs. Osteotomy lines were classified into three types: vertical, C-shaped, and oblique. Of the 185 osteotomy sites, 98 were vertical, 37 C-shaped, and 50 oblique. Condylar luxation was found in six rami (3.2%); four had undergone vertical osteotomy and two had undergone C-shaped osteotomy. Bony interference occurred in seven rami (3.8%), all with vertical type osteotomy lines. Most complications occurred in the vertical type cases and no complications were found in oblique type cases. Condylar luxation was found mainly in unilateral IVRO cases and bony interference was found in bilateral IVRO cases. These results suggest that the oblique type of osteotomy line has the advantage of avoiding complications.
Intraoral vertical ramus osteotomy (IVRO) is one of the popular surgical methods to correct mandibular prognathism. It is also called transoral ramus osteotomy, and is a preferred technique for treating patients with symptomatic temporomandibular joint (TMJ) disorders. IVRO improves the disc–condyle relationship in patients with mandibular deformities, providing good postoperative stability and patient satisfaction. IVRO can be used either bilaterally or unilaterally with a sagittal split ramus osteotomy (SSRO) on the contralateral side to correct mandibular asymmetry. IVRO is sometimes the preferred surgical method to SSRO for the correction of mandibular prognathism.
IVRO has several advantages over SSRO. IVRO is a technically simple procedure that does not require internal fixation. It reduces the surgical time and bleeding, and is less likely to cause facial or inferior alveolar nerve injury. However, IVRO has some disadvantages compared with SSRO. The most common complication is condylar displacement or luxation from the glenoid fossa. The extent of medial pterygoid muscle stripping is considered to be a causal factor of this complication. Another major complication is bony interference between the proximal and distal segments. These complications have been considered to be related to the lack of internal fixation and inadequate setback. The shape of the osteotomy line may be a causal factor of these complications, but no study has been conducted to determine the association between the shape of the osteotomy line and the incidence of complications after IVRO. The aim of this study was to survey the incidence of complications after bilateral or unilateral IVRO, focusing on the shape of the osteotomy line.
Materials and methods
Patients and surgical treatments
The present study was a non-randomized retrospective study of all patients treated with IVRO in the University of Tokyo Hospital from August 2001 to December 2013. One hundred and eighteen Japanese patients (54 male, 64 female) were examined. All patients who underwent IVRO were candidates for this study. IVRO was performed bilaterally (67 cases) or unilaterally (51 cases) in 185 rami, either with (82 cases) or without (36 cases) maxillary advancement. The features of the jaw deformities were mandibular prognathism with/without maxillary retrusion and/or facial asymmetry. The age of the patients at the time of orthognathic surgery ranged from 15 to 54 years (mean 23.8 years, median 21.0 years).
IVRO procedures were basically performed according to Bell’s technique. In the study institution, IVRO is usually used in patients with less than 5 mm of setback. The medial pterygoid muscle was not generally stripped, but was minimally stripped occasionally. In the case of unilateral IVRO, an SSRO was performed on the contralateral ramus. Although rigid fixation using miniplates or monocortical screws was performed in the SSRO procedure, the mandibular segments were left unfixed with IVRO. Maxillomandibular fixation was placed at 1–5 days after surgery using wires or elastics. All patients received pre- and postoperative orthodontic treatment. In cases of condylar luxation, reduction of the condyle to the proper position was performed with additional surgery. In cases of bony interference, the causal part of bone near the osteotomy line was removed surgically in all cases except one.
Osteotomy line classification and presence of complications
The shape of the osteotomy line and the presence of complications after IVRO were determined on panoramic radiographs taken 3–5 days after surgery. The shape of the osteotomy line was classified into three types: type 1, vertical (the ramus was sectioned vertically from the mandibular notch to the antegonial notch); type 2, C-shaped (the ramus was sectioned with curvature to avoid the mandibular foramen); and type 3, oblique (the ramus was sectioned obliquely from mandibular notch to mandibular angle) ( Fig. 1 ).
The presence of condylar luxation and bony interference were examined as complications ( Fig. 2 ). Three experienced oral surgeons identified and recorded the osteotomy types and complications; in the case of disagreement between examiners, the final decision was made by consensus.
Differences in the results among the three osteotomy shape types and between bilateral and unilateral IVRO were examined using Fisher’s exact test. Differences were considered significant at P < 0.05.
Of the 185 rami examined, 98 had a vertical type osteotomy (53.0%), 37 had a C-shaped type (20.0%), and 50 had an oblique type (27.0%) ( Fig. 3 ). Complications (condylar luxation or bony interference) were found in 13 rami (7.0%). The association between the shape of the osteotomy line and the incidence rate of complications is shown in Fig. 4 . Eleven rami treated with vertical type osteotomies (11.2% of vertical types) and two treated with C-shaped osteotomies (5.4% of C-shaped type) showed complications. No complications were found in rami treated with oblique type osteotomies. However, a statistically significant difference was not found between the vertical and the C-shaped types ( P = 0.513).