DIFFERENT TREATMENT MODALITIES FOR PARASYMPHYSIS FRACTURES- A COMPARATIVE EVALUATION

The incidence of mandibular fracture in day to day Oral and Maxillofacial practice is quite high. Among various types of mandibular fractures, incidence of parasymphysis fracture is about 13%. The management of mandibular fractures has undergone various changes right from 17th century BC till today. These techniques has ranged from closed reduction with maxillomandibular fixation (MMF), to open reduction with wire osteosynthesis or rigid internal fixation or miniplate fixation. The introduction of bone plates as the implants for osteosynthesis has changed the facet of oral and maxillofacial surgery. The concept of bone plating has changed over time, with the introduction of various modifications. Bone plates such as microplates, miniplates, reconstruction plate, compression plates, dynamic compression plates, eccentric dynamic compression plates, have been introduced, but miniplates are the ones most commonly used.1,2 In 1970 Champy et al determined the ideal line of osteosynthesis in the mandible, where they suggested that miniplate fixation is most stable6. According to Champy, tensile forces exist at the superior border of the mandible and compressive forces at its inferior border. In the parasymphysis region, another line is drawn near the lower border to neutralize the tension forces; as torsional forces in the parasymphysis region are high 7-8. The principle of osteosynthesis, according to Champy, is to re-establish the mechanical qualities of the mandible 9. Champy advised the use of two miniplates in the anterior region, one at the inferior border and the second 5 mm above the lower plate. This Champy’s principle is still followed, but the need for two miniplates in the parasymphysis region is questioned, when a lower arch bar is also placed simultaneously for intra or postoperative maxillo-mandibular fixation. Though Champy did not use arch bars for intra-operative inter-maxillary fixation, most surgeon use arch bars either for intra-operative or post-operative inter-maxillary fixation itself acts as a tension band and sub-apical plate (tension band plate) can be eliminated. Since a single miniplate is used instead of two plates it will be economical for the patients, reduce the incidence of mental nerve injury and will reduce injury to the roots of the anterior teeth and reduce wound dehiscence. 10,11 In this study, three different modalities for treating isolated displaced mandibular parasymphysis fracture are compared. The objectives of the study is to compare three different treatment modalities clinically and radiographically by assessing, discrepancy in the occlusion, anaesthesia or paraesthesia due to mental nerve injury, evidence of infection at the operated site, exposure of osteosynthesis implants, intra-operative time taken for the procedure, lower border malalignment, loosening of screws or plates, and improper reduction of fracture fragment. 12 This study was designed with an aim of to compare the stability and efficacy of different treatment modalities for parasymphysis fracture. Patients were randomly divided into 3 equal groups of 10 patients each. Group I patients underwent two mini plates placed across the fracture site along with Erich’s arch bar for six weeks. In Group II patients underwent two mini plates placed across the fracture site without Erich’s arch bar. In Group III patients underwent single mini plate placed across the fracture site along with Erich’s arch bar for six weeks.The resulting osteosynthesis were compared for eight parameters and complications in either of the procedures were noted. The age of patients were ranged from 18 to 65 years. There were 25 (83 %) males and 5 (17%) female patients. The procedures were done either under local anaesthesia with sedation or under general anaesthesia. Patients were kept on regular follow up on immediate post-operative period, 15th day, Ist month, 3rd month and 6th month post-operatively and evaluated for the treatment results and complications. The following conclusions could be drawn from the study: 1) Young adult males were most commonly affected with parasymphysis fracture.(83%) 2) Difference in incidence of loosening of screws/plates among the groups were not found significant. 3) Difference in incidence of inferior border malalignment among the groups were not found significant. 4) Difference in incidence of improper reduction of fractured segments among the groups were not found significant. 5) Incidence of signs of paraesthesia, at immediate post-operative period were found in 3 patient of Group I, 2 patient of Group II and none patient of Group III, but difference in incidence of signs of paraesthesia among the groups were not found significant. 6) Difference in incidence of occlusal discrepancy among the groups were not found significant. 7) Difference in incidence of exposure of implant among the groups were not found significant. 8) Difference in incidence of infection/ wound dehiscence among the groups were not found significant, however the infection was reported to be higher in Group I. 9) Difference in duration of surgery between Group I & Group II was not found to be statistically significant while difference between Group I & Group III and between Group II & Group Group III was found to be statistically significant. Order of duration of surgery was- Group III < Group II ? Group I. The outcome of the present study suggested that isolated parasymphysis fractures can be managed by using a single miniplate along with an Erich arch bar for 6 weeks, which will act as a tension band. This reduces the intra-operative time. It is economical for the patient as one miniplate is used instead of two. The use of single miniplate causes minimum injury to the mental nerve in the case of a fracture line running close to the mental foramen. It can be concluded that though miniplates are best placed following Champy’s principle, isolated parasymphysis fractures can be managed by putting a single miniplate at the inferior border and utilizing the arch bar as a tension band for 6 weeks. The small sample size and limited follow up could be considered as the limitations of this study. It is recommended to have a multicentre study with large number of patients and correlation among these studies to authenticate our claims.