[Mechanism of the formation of orbital floor fractures. Holographic interferometry studies].

To date, it has not been possible to answer the question of whether in the classic blow-out fracture the orbital floor is fractured by hydraulic force exerted by the orbital contents or by force transmission within the bony structures of the skull. The aim of our investigation was therefore to reveal the nature of orbital deformation mediated solely by the bone. In holographic interferometry the holographic image of the unstrained object is superimposed on the image of the same object after deformation. The resulting image of the object contains a pattern of interference lines representing the extent of the deformation. This image can be visualized on a TV screen after digital processing of a picture registered by a video camera. This method was used to analyze the deformation of the bony orbit by contact force applied to several points along the orbital rim (each application consisting of 1 N) and by strain distributed evenly upon the orbital rim of the human skull. In all cases maximal deformation occurred in the medial part of the orbital floor no matter where the stress was applied. This finding coincides with the fact that the majority of clinically diagnosed fractures are found in this area. In conclusion, force transmission within the bone is considered as being one determining factor for occurrence of orbital floor fractures.