Biomechanical evaluation of Le Fort I maxillary fracture plating techniques.

PURPOSE

This study used a biomechanical model to examine fundamental questions about rigid plate fixation treatment for maxillary Le Fort I fractures. Specifically, we sought to elucidate the principal strain patterns generated in miniplates and bite force transducers secondary to all masticatory forces, as well as the amount of permanent deformations incurred due to these loading forces.

MATERIALS AND METHODS

Forty polyurethane synthetic maxillary and mandibular replicas were used to simulate the mandible and maxilla. Ten replicas were controls (group A). The other 30 were divided into 3 groups (10 each), according to the fixation techniques of 3, 2, and 1 miniplates each side (groups B-D), that were osteotomized in the Le Fort I fracture line on the maxilla. Different forces of masseter medial pterygoid, temporalis, and lateral pterygoid muscles were loaded onto the replicas to simulate different functional conditions (anterior incisor, premolar, and molar clenching). Rosette strain gauges were attached at predefined points on the plates and the bite force transducer to compare the stability and bite force of the different fixation methods for maxillary Le Fort I fractures.

RESULTS

Statistically significant differences were found for the deformation of the plates among fixation techniques. The order of stability for each technique was: group B greater than group C greater than group D. In regard to bite force, no difference was found between those found with group A and group B (P > .05), whereas the bite forces of groups C and D were less than those of group A (P < .05).

CONCLUSIONS

The fixation of 3 miniplates on each side provides sufficient stability and restores the bite force to the level of the intact maxilla. "The ideal fixation" with 2 miniplates on each side restores 90% of the bite force, and there were more deformations of the miniplates with the "ideal fixation" compared to those found with group B. Group D fixation produced the worst effects for the treatment of maxillary Le Fort I fractures with a weak bite force and insufficient stability.