Preoperative and Postoperative CT Scan Assessment of Pterygomaxillary Junction in Patients Undergoing Le Fort I Osteotomy: Comparison of Pterygomaxillary Dysjunction Technique and Trimble Technique—A Pilot Study

Abstract

Purpose To determine the rate of complications and occurrence of pterygoid plate fractures comparing two techniques of Le Fort I osteotomy i.e., Classic Pterygomaxillary Dysjunction technique and Trimble technique and to know whether the dimensions of pterygomaxillary junction [determined preoperatively by computed tomography (CT) scan] have any influence on pterygomaxillary separation achieved during surgery. Materials and methods The study group consisted of eight South Indian patients with maxillary excess. A total of 16 sides were examined by CT. Preoperative CT was analyzed for all the patients. The thickness and width of the pterygomaxillary junction and the distance of the greater palatine canal from the pterygomaxillary junction was noted. Pterygomaxillary dysjunction was achieved by two techniques, the classic pterygomaxillary dysjunction technique (Group I) and Trimble technique (Group II). Patients were selected randomly and equally for both the techniques. Dysjunction was analyzed by postoperative CT. Results The average thickness of the pterygomaxillary junction on 16 sides was 4.5 ± 1.2 mm. Untoward pterygoid plate fractures occurred in Group I in 3 sides out of 8. InTrimble technique (Group II), no pterygoid plate fractures were noted. The average width of the pterygomaxillary junction was 7.8 ± 1.5 mm, distance of the greater palatine canal from pterygomaxillary junction was 7.4 ± 1.6 mm and the length of fusion of pterygomaxillary junction was 8.0 ± 1.9 mm. Discussion The Le Fort I osteotomy has become a standard procedure for correcting various dentofacial deformities. In an attempt to make Le Fort I osteotomy safer and avoid the problems associated with sectioning with an osteotome between the maxillary tuberosity and the pterygoid plates, Trimble suggested sectioning across the posterior aspect of the maxillary tuberosity itself. In our study, comparison between the classic pterygomaxillary dysjunction technique and the Trimble technique was made by using postoperative CT scan. It was found that unfavorable pterygoid plate fractures occurred only in dysjunction group and not in Trimble technique group. Preoperative CT scan assessment was done for all the patients to determine the dimension of the pterygomaxillary region. Preoperative CT scan proved to be helpful in not only determining the dimensions of the pterygomaxillary region but we also found out that thickness of the pterygomaxillary junction was an important parameter which may influence the separation at the pterygomaxillary region. Conclusion No untoward fractures of the pterygoid plates were seen in Trimble technique (Group II) which makes it a safer technique than classic dysjunction technique. It was noted that pterygoid plate fractures occurred in patients in whom the thickness of the pterygomaxillary junction was \3.6 mm (preoperatively). Therefore, preoperative evaluation is important, on the basis of which we can decide upon the technique to be selected for safer and acceptable separation of pterygomaxillary region.

The pterygomaxillary junction: An imaging study for surgical information of LeFort I osteotomy

“…Consistent with our results, several other researchers have found a negative correlation between the thickness of the pterygoid junction and the occurrence of the pterygoid plate fracture 5 , 21 , 22 . They hypothesized that when the pterygomaxillary junction is thin, the force from the osteotome may be easily dissipated leading to unwanted pterygoid plate fracture.…”

“…In an attempt to avoid these complications, some authors perform the osteotomy through the maxillary tuberosity, as described by Trimble 35 . They asserted that it reduced unfavorable fractures of the pterygoid plates 36 compared to traditional disjunction, and also increases the safety margin to the structures of the sphenopalatine fossa, reducing the incidence of hemorrhages 21 , 35 . One drawback is that the method can only be performed if the wisdom teeth are removed.…”

Three-dimensional descriptive study of the pterygomaxillary region related to pterygoid implants: A retrospective study

“…The width of the pterygomaxillary joint has been previously studied in articles related to surgical techniques such as Le Fort I osteotomies 27,28 . However, we have not been able to find research focused on implantology that evaluates this characteristic.…”

“…As for the angulation of the pterygoid implants with respect to the Frankfort plane, there is no consensus. Different authors defend their placement with an approximate angle of 45° 13,15,35 while in more recent studies their placement is defended at an angle of 70° 27–35 . In a study developed by Rodríguez et al .…”

Three-dimensional finite element model to predict patterns of pterygomaxillary dysjunction during Le Fort I osteotomy

“…Therefore, Dadwal et al suggested that the 'Trimble technique' be applied, in which a vertical cut is made on the tuberosity in the third molar region, avoiding unfavourable pterygoid process fracture during LFI. 36 The present authors believe that, when cutting the pterygomaxillary junction, all the stress produced by the separation force is concentrated on the pterygoid process, leading to pterygoid process fracture. Therefore, in order to prevent pterygoid process fracture, the cut in the lateral wall of the maxilla should be limited to the middle point between the distal plane of the second molar and the pterygomaxillary junction.…”