Abstract
Maxime Champy advised the use of two miniplates for parasymphysis fractures because of the high torsional forces in the anterior region of the mandible. According to him there is no need for intraoperative or postoperative intermaxillary fixation, but most surgeons use arch bars for intraoperative or postoperative intermaxillary fixation. This study evaluated the role of the lower arch bar as a tension band eliminating the need for an upper miniplate (tension band plate) in cases of parasymphysis fractures. 3 groups underwent treatment. In the first group, two titanium miniplates were placed across the fracture site along with Erich’s arch bar for 6 weeks. In the second group, two titanium miniplates were used for osteosynthesis without Erich’s arch bar. In the third group, one titanium miniplate was placed along with Erich’s arch bar for 6 weeks. The results of third group were statistically non-significant compared with those of the first and second groups.
The introduction of bone plates as the implants for osteosynthesis has changed this facet of oral and maxillofacial surgery. The concept of bone plating has changed over time, with the introduction of various modifications. Sequentially, bone plates such as compression plates, dynamic compression plates, eccentric dynamic compression plates, miniplates and microplates have been introduced; but miniplates are the ones most commonly used.
In the early 1970s, Champy et al. determined ‘the ideal line of osteosynthesis’ in the mandible, where they suggested that miniplate fixation is most stable. According to Champy, tensile forces exist at the superior border of the mandible and compressive forces at its inferior border. Tensile forces exist at the superior border of the mandible due to continuous functions of the stomatognathic system which causes distraction at the site. The distraction of the alveolar border at this site must be prevented to achieve uniform compression across the length of fracture. This brought about the need for tension bands, which can be in the form of a small miniplate at the superior border or in the form of various arch bars at the alveolar segment. In the mandible, a line drawn at the base of the alveolar process corresponds to the line of tension and monocortical plates and screws can be fixed along this line. 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. The principle of osteosynthesis, according to Champy, is to re-establish the mechanical qualities of the mandible. 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 surgeons use arch bars either for intra-operative or postoperative inter-maxillary fixation. The lower arch bar placed for intra-operative or postoperative inter-maxillary fixation itself acts as a tension band and the 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 patient, will reduce the incidence of infection, will reduce the incidence of mental nerve injury and will reduce injury to the roots of the anterior teeth and reduce wound dehiscence.
In this study, three different modalities for treating isolated displaced mandibular parasymphysis fractures are compared. The objectives of the study were 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 fragments.
Materials and methods
This study was undertaken in the authors’ department of oral and maxillofacial surgery, with permission from the ethical committee. 30 patients reporting to the department with a history of trauma having isolated displaced parasymphysis fractures were included in the study. The patients were randomly assigned to 3 equal groups. Preoperative variables were almost similar in all the three groups.
Patients with an isolated parasymphysis fracture with occlusal discrepancy and without any signs or symptoms of mental nerve injury were included in the study. Patients were excluded from the study if they had: edentulous mandible; parasymphysis fractures associated with other mandibular or facial bone fractures; no indication for or unwilling to undergo open reduction with internal fixation; or severely comminuted and infected fractures.
In the first group, two titanium miniplates were placed across the fracture site along with lower Erich’s arch bar for 6 weeks ( Fig. 1 ). In the second group, two titanium miniplates were used for osteosynthesis without Erich’s arch bar ( Fig. 2 ). In the third group, one titanium miniplate was placed along with the lower Erich’s arch bar for 6 weeks ( Fig. 3 ). In all 3 groups, 2.5 mm plates were used and the screws used for fixation were 8 mm long and of the monocortical type.
After ruling out head injury and cervical spine injury in the patients and ensuring their complete stabilization, surgery was undertaken. All routine investigations were carried out preoperatively. Preoperatively, an orthopantomogram (OPG) was taken for all the patients for radiographic interpretation of the fracture site.
Oral prophylaxis was carried out before the commencement of surgery. Erich’s arch bars were placed in the upper and lower arches one day prior to surgery in all patients for intra-operative inter-maxillary fixation. After obtaining consent from the patients and their relatives for the surgery, the operation was carried out under general anaesthesia for open reduction and internal fixation. Naso-endotracheal intubation was used in all cases. Scrupulous disinfection of the oral cavity was carried out with chlorhexidine in all cases. In all the groups, an intra-oral incision was made in the lower vestibule, 4–5 mm below the level of attached gingival, in the alveolar mucosa. After exposing the fracture site by careful periosteal elevation, loose ragged tissue, foreign bodies, debris, and loose bony fragments were removed. Reductions of the fractured segments were made and temporary inter-maxillary fixation was done in that reduced position.
The fractured segments in the first group were fixed using two titanium miniplates of 2.5 mm diameter with 2.5 mm × 8 mm monocortical titanium screws. The upper plate was a 3 hole plate, fixed so that one hole lay on each side of the fracture line. The lower plate was a 5 hole plate with 2 holes on each side of the fracture line. These two plates were placed according to the ideal osteosynthesis lines given by Champy to prevent torsion movements. First, the inferior plate was placed and later another 3 hole sub-apical plate was placed 4–5 mm above the inferior plate. After plate fixation, the operated area was irrigated with 5% betadine mixed with normal saline. Suturing was done in two layers. The arch bars were removed after 6 weeks.
In the second group, two miniplates were placed in the same manner as in the first group. Arch bars were placed only for intra-operative inter-maxillary fixation and, on the first postoperative day, the arch bars were removed in this group of patients.
In the third group, a single 2.5 mm titanium miniplate was placed at the inferior border in the same manner as in the first group. A second sub-apical plate was not used in this group. A lower Erich’s arch bar was used as a tension band which was removed after 6 weeks.
Patients in all three groups were hospitalized for 5 days and were given intravenous antibiotics. All patients were followed up for 6 months and were assessed clinically and radiographically by taking OPGs at each follow-up visit. Assessment was made on the immediate postoperative day, after 15 days, then at 1 month, 3 month and 6 month interval. Following criteria were included in the study: any occlusal discrepancy; any sign of infection or wound dehiscence at the operated site; any symptom or sign of anaesthesia or paraesthesia; exposure of the implant; intra-operative time taken for the procedure; improper reduction of fractured segments; inferior border malalignment; and loosening or fracture of osteosynthesis implants. Clinically, mental nerve injury was checked by using static light touch, two point discrimination, brush directional discrimination and pin pressure methods.
Data were analysed and statistical analysis was applied using the graph pad prism version 5 ( χ 2 trend test). The three groups were compared on the basis of qualitative data. Seven clinical and radiographic parameters, which included occlusal discrepancy, evidence of infection, signs of anaesthesia or paraesthesia, evidence of exposure of implant, improper reduction of fractured segments, inferior border discrepancy and loosening of screws were analysed at intervals of 0 day, 15 days, 1 month, 3 months and 6 months. Intra-operative time was compared on the basis of quantitative data using an ANOVA test ( Tables 1–8 ).
| Time period | Group I | Group II | Group III |
|---|---|---|---|
| Immediate postoperative period | – | – | – |
| 15 days | – | – | – |
| 1 month | – | – | – |
| 3 months | – | – | 1 |
| 6 months | – | – | 1 |
| Statistical analysis | χ 2 = 4.29 p value = 0.11 ( p > 0.05) Not significant |
||
| Time period | Group I | Group II | Group III |
|---|---|---|---|
| Immediate postoperative period | – | 1 | 1 |
| 15 days | – | 1 | 1 |
| 1 month | – | 1 | 1 |
| 3 months | – | 1 | 1 |
| 6 months | – | 1 | 1 |
| Statistical analysis | χ 2 = 0.71 p value = 0.58 ( p > 0.05) Not significant |
||
| Time period | Group I | Group II | Group III |
|---|---|---|---|
| Immediate postoperative period | – | 1 | 1 |
| 15 days | – | 1 | 1 |
| 1 month | – | 1 | 1 |
| 3 months | – | 1 | 1 |
| 6 months | – | 1 | 1 |
| Statistical analysis | χ 2 = 0.71 p value = 0.58 ( p > 0.05) Not significant |
||
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