[New experimental insights into the mechanism of blow-out fractures]

Model impact tests on 3-dimensional PMMA eye models with a swing type impact tester (Dynstat) were performed. There are three kinds of impact tests; the impact to the eyeball alone, the impact to the eyeball and infraorbital margin, and the impact to the isolated infraorbital margin. All impact tests of eye models were recorded by high speed camera with 3,000 pictures per second. Analysis of impact tests showed, that the primary factor of blow-out fractures was deformation of the eyeball by kinetic energy of impact. Transmission of impact force by deformed eyeball to orbital walls is causing blow-out fractures on the weakest areas of the orbit without fracturing the orbital rim. Against the present accepted theories of "hydraulic force" und "buckling force" this is a new theory for pathomechanism of blow-out fractures. Our experimental results support the clinical investigations on treated patients.