Open reduction and internal fixation of acute mandibular fractures in adults

An In Vitro Evaluation of a Novel Design Z Plate for Fixation of Mandibular Symphysis and Parasymphysis Fractures-A Finite Element Analysis

Aim

Surgical management of mandibular symphysis and parasymphysis fractures has evolved from rigid fixation to semi-rigid fixation with miniplate osteosynthesis. Various miniplate systems have been developed in recent years including three-dimensional miniplate, microplates and bioresorbable plate, and their advantages and disadvantages have been compared and studied. To overcome the shortcomings of 3D plating system such as difficulty in adaptation and fixation in fractures involving the mental nerve, a novel Z plate has been designed by our institute.

Material and Methodology

An in vitro study was performed to evaluate the biomechanical behaviour of the newly designed Z plate with 3D plate and two-miniplate system using finite element analysis.

Results

Our study showed total structural deformation of 0.17 mm and 0.31 mm of newly designed Z plate after canine loading and molar loading, respectively. The equivalent von Mises force for plate after canine loading had shown the following results-Z plate showed values of 121.3 MPa and 58.40 MPa after molar loading.

Conclusion

Our study concluded that the Z plate produces lowest stresses, lesser total structural deformation, superior stability and support in comparison with the 3D plate and two-miniplate system.

A clinical prospective randomized comparative study on ostyeosynthesis of mandibular anterior fractures following open reduction using lag screws and miniplates

Introduction

The aim of the present study was to compare fixation of mandibular anterior fractures following open reduction using lag screws or miniplates.

Materials and Methods

This prospective study was conducted on 20 patients diagnosed with cases of displaced mandibular anterior fractures treated with open reduction and internal fixation. The patients were then randomly allocated to either of two groups - Group A: two 2.5 mm stainless steel lag screws were placed in 10 patients. Group B: two 2.5 mm miniplates were placed in 10 patients for the fixation of fractures. Subsequent follow-up was done on the 1^st day, 1^st, 4^th, and 36^th week postoperatively. During every follow-up, patient was assessed clinically for infection, malocclusion, loosening of plate/screw, malunion/nonunion, and masticatory efficiency. Radiographs (orthopantogram) were taken preoperative, 1^st, 4^th, and 36^th postoperative week to compare the osteosynthesis between the two groups. Pain was objectively measured using a visual analog scale. The data collected was subjected to unpaired t-test and paired t-test for statistical analysis.

Result

It was found that lag screw placement was rapid in comparison of miniplate placement. 3rd month postoperative assessment revealed Lag screw group to have better biting efficiency, and better bone healing which was statistically significant when compared with miniplate group.

Conculsion

Our study suggests that lag screw osteosynthesis can be advocated as a valid treatment modality in the management of mandibular symphysis and parasymphysis fractures.

The biophysics of mandibular fractures: an evolution toward understanding

BACKGROUND

Predicting outcomes based on a variety of fixation techniques remains problematic in the treatment of mandible fractures. There is inherent difficulty in comparing the hundreds of published articles on the subject because of the large number of variables, including injury patterns, assessment techniques, treatment approach, device selection and application, and definition of outcome.

METHODS

The authors review the behavior of the human mandible. Behavior of the intact mandible, multiple fracture scenarios, and small and large (single and multiple) plating applications are reviewed.

RESULTS

Several misconceptions in the literature are clarified. Factors that will resolve the dichotomy between clinical results and current biomechanical theories are presented such that a more logical biomechanical model may be used to approach fixation of the mandibular fracture being treated.

CONCLUSIONS

Current mandibular biomechanics theory must be expanded to reflect the complex nature of the system and to more accurately describe conditions that exist in the physical world. Otherwise, further analysis in advancements in outcome and treatment will be relegated to chance.

Evaluation of osteotomy fixation changing the number, the extension and the location of the plates

We used a two-dimensional model that simulated a fractured human mandible to study the extent of load resistance of different plates. We studied 49 bovine ribs in seven groups using varying number (1 or 2), lengths of plates (4 or 6-holes), and location (near the lower or upper border). The number and location of plates had a greater effect on resistance to load than length of plates. The best mean resistance values were achieved by a combination of two parallel plates secured near the lower and upper borders, followed by single plates secured near the upper border. The lowest values were with single plates secured close to the lower border.

A three-dimensional numerical simulation of mandible fracture reduction with screwed miniplates

A three-dimensional finite element model of a fractured human mandible treated with plating technique was developed to simulate and to study the biomechanical loads and the stress field distribution. Biomechanical properties of bone have been thoroughly investigated experimentally. In this work, using the finite element method, complete clinical conditions (after surgical reduction, post-operatory period, complete healing period) were simulated. The mandible fracture was located in the symphysis region and one or two titanium miniplates, fixed with monocortical screws, were evaluated. The behaviour of a reduced human mandible with screwed miniplates, as well as its complete healing, is investigated and described.

Combination of microplate and miniplate for osteosynthesis of mandibular fractures: an experimental study

Because of the limited space available in the mandible, especially in the mental foramen and apical region, miniature osteosynthesis material is desirable. Recently, metal deposition in the direct neighbourhood of osteosynthesis plates made of titanium or even in peripheral organs have been reported in the literature with increasing frequency. The size and amount of osteosynthesis material used should therefore be kept to a minimum. In an experimental study on 60 models, we examined load-carrying stability and in a second series, torsional strength of two-piece plastic models connected by either a single miniplate, two miniplates, or a titanium microplate plus a miniplate. In our test arrangement, the average loading capacity of the combination miniplate/miniplate was 470 N: that of the combination microplate/miniplate was only 267 N. The test group with the single miniplate had an average loading capacity of only 225 N. Masticatory loads on the plates exceeding 200 N occur only 3 months after osteosynthesis. At that time the fracture has largely consolidated. The torsional strength of the microplate/miniplate combination was similar to that of the miniplate/miniplate combination (1,000 Nmm resulting in a width of the gap measuring 0.8 mm and 0.5 mm, respectively). The single miniplate was considerably less stable (0.8 mm gap width as early as with 300 Nmm). According to Champy, rotational forces in the anterior region of the mandible amount to approximately 1,000 Nmm and need to be withstood by the osteosynthesis material. Our results suggest that treatment of fractures in the interforaminal region with a combination of microplate and miniplate will be stable enough for early mobilization.