Experimental evaluation of three osteosynthesis devices used for stabilizing condylar fractures of the mandible.
BACKGROUND
The purpose of the study is to evaluate experimentally the quality of the primary stability achieved in treating low subcondylar fractures by means of three different osteosynthesis devices.


METHODS
The devices, a standard four-hole plate, an axial lag screw and a three-dimensional rectangular plate were tested on fresh isolated human mandibles. Testing was done on a test bench by reproducing static biting exercises between the first molars on the side of the fracture. The quality of the osteosynthesis was assessed by measuring the macroscopic amount of fragment displacement and on the device's ability to diffuse the mechanical strain within the fractured area by photoelastic stress analysis.


RESULTS
The straight plates provided the worst restoration. This was explained by the unfavourable position of the plate along compression lines. The axial lag screws allowed average stability. This was due to the difficulty of intra-medullary positioning of the screw, and by the compression of the fracture line. Rectangular plates allowed good stability associated with rather good restitution of the strains. These good results were assigned to the shape of the plate, one of its arms approximating the tensile strain lines.


CONCLUSIONS
Positioning and shape of the osteosynthesis device are of prime importance for condylar fracture stabilization. None of the three tested devices was optimal but the three-dimensional plate was the best. There is a need to develop the geometry of new plates.
Department of Maxillofacial Surgery, University Hospital of Strasbourg, France. Christophe.Meyer@chru-strasbourg.fr
Christophe
C
Meyer
Leila
L
Serhir
Philippe
P
Boutemi
D001732:Bite Force; D001860:Bone Plates; D001863:Bone Screws; D003799:Dental Stress Analysis; D004867:Equipment Design; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D007572:Jaw Fractures / Q000601:surgery*; D008335:Mandibular Condyle / Q000293:injuries* / Q000601:surgery; D013314:Stress, Mechanical