Reduction and Fixation of Mandibular Condylar Fractures With Neck Screw:

Does lag screw fixation of condylar fractures result in adequate stability? A finite element analysis

The great incidence and controversies related to the diagnosis, treatment, surgical accesses, and type of osteosynthesis materials confer an outstanding role to condylar fractures among facial fractures. Plate configurations, with diverse formats and sizes, may be used to surgically resolve condylar fractures. With the purpose of improving the advantages and minimizing the disadvantages of fixation techniques, the neck screw was developed aiming at the needed stabilization to render a correct fixation through a system of dynamic compression. This is achieved by increasing the contact between the fractured bone stumps, as well as assisting at the time of fracture reduction. The present paper aims at comparing the fixation and stability of mandibular condylar fractures using the neck screw and an overlaid "L"-shaped-4-hole-2 mm plate on the one hand, with a system in which the neck screw and the "L"-shaped plate form a single structure, having been joined by a welded point, on the other hand. The results with the neck screw are satisfactory, and, thus, it is an alternative for the reduction and fixation of fractures of the mandibular condyle, whether or not a plate is joined to the structure, provided it is correctly prescribed and with adequate surgical sequence and technique.

In-vitro comparison of mechanical resistance between two straight plates and a Y-plate for fixation of mandibular condyle fractures

OBJECTIVE

To compare the mechanical resistance of conventional plates with a modified Y-plate in mandibular condyle fracture.

MATERIALS AND METHODS

40 synthetic hemi-mandibular polyurethane replicates were used. Two groups of fixing materials were included: 20 mandibles fixed with 40 straight plates with four roles each (2.0 mm system) and 20 mandibles fixed with 20 Y-shaped plates (2.0 mm system and 1.5 mm thickness). The samples were submitted to linear loading in the following directions: 10 mandibles from each group from lateral to medial and 10 mandibles from each group from anterior to posterior. A universal loading machine, Instron Universal 4411, was used to performed the tests, and the resistance of each fixed mandible was assessed at displacements of 1 mm, 3 mm, and 5 mm. The t-test for independent samples was performed. The p value was set at <0.05.

RESULTS

The worst mechanical resistance was found in the Y-plates loaded from anterior to posterior. The best mechanical resistance was in two straight hole plates loaded from lateral to medial. The Y-plates and two straight hole plates showed similar resistance when a lateral to medial load was applied.

CONCLUSION

There was no difference between the plates when lateral to medial loading was tested.

Comparison of Neck Screw and Conventional Fixation Techniques in Mandibular Condyle Fractures Using 3-Dimensional Finite Element Analysis

PURPOSE

To compare the mechanical stress on the mandibular condyle after the reduction and fixation of mandibular condylar fractures using the neck screw and 2 other conventional techniques according to 3-dimensional finite element analysis.

MATERIALS AND METHODS

A 3-dimensional finite element model of a mandible was created and graphically simulated on a computer screen. The model was fixed with 3 different techniques: a 2.0-mm plate with 4 screws, 2 plates (1 1.5-mm plate and 1 2.0-mm plate) with 4 screws, and a neck screw. Loads were applied that simulated muscular action, with restrictions of the upper movements of the mandible, differentiation of the cortical and medullary bone, and the virtual "folds" of the plates and screws so that they could adjust to the condylar surface. Afterward, the data were exported for graphic visualization of the results and quantitative analysis was performed.

RESULTS

The 2-plate technique exhibited better stability in regard to displacement of fractures, deformity of the synthesis materials, and minimum and maximum tension values. The results with the neck screw were satisfactory and were similar to those found when a miniplate was used.

CONCLUSION

Although the study shows that 2 isolated plates yielded better results compared with the other groups using other fixation systems and methods, the neck screw could be an option for condylar fracture reduction.