Positioning Measurement And Finite Element Analysis Of Orbito-Facial Structures:from Establishments To Clinical Applications

ObjectivesOrbito-facial structures were to be located and measured in a three-dimensional(3D)coordinate system established in this study.Finite element models were to be built for bony orbit and intra-orbital tissues.Impact dynamic experiments were to be conducted to study the mechanisms and influence factors of orbito-facial blunt injuries.Clinical researches on orbito-facial injuries were to be done.Materials and methods1)Computer programs were written to build a standard orbital three-dimensional coordinate system on the basis of thin computed tomographic(CT)images.2)Normal intra-orbital structures were located and measured in this coordinate system.3)Finite element models were built for bony orbit and intra-orbital tissues.4)Impact dynamic experiments were performed with the finite element models to imitate the mechanisms of orbital blowout fracture and open globe injury.5)The causes,outcomes and influence factors of open globe injury were retrospectively investigated.6)For the cases of orbital blowout fractures,displacements of orbital walls and late displacement of the eyeball were measured in the three-dimensional coordinate system.Results1)The establishment method of the orbital three-dimensional coordinate system had high reproducibility.2)The normal locations and measurements of orbito-facial structures were determined in the coordinate system.Normal intra-orbital structures were bilaterally symmetric and had sexual dimorphism.Some morphological variables were correlated.3)Finite element models of bony orbit and intra-orbital tissues were established.Volume and detailed CT value of these models were determined.4)Low speed blunt impact could cause orbital blowout fracture,whereas high speed blunt impact could cause open globe injury.Thin and vulnerable regions in orbital walls could protect the eyeball from rupture in certain cases of blunt trauma.Orbital wall implant of rigid material could not provide this protection.5)Major causes,outcomes and influence factors of open globe injury were found out.Classification and regression tree(CART)could predict final visual outcome.6)In the cases of orbital blowout fractures,late displacement of the eyeball was correlated with the displacements of orbital walls.The fracture sites were located mostly posterior to the center of the unaffected eyeball.The same extent of orbital wall displacement caused more displacement of the eyeball in females than in males.Conclusions1)Orbito-facial structures could be located and measured in the standard orbital three-dimensional coordinate system established in this study.2)Normal orbito-facial structures were bilaterally symmetric and had sexual dimorphism.3)Finite element models could be used to study the morphological and material properties of orbito-facial structures.4)Impact dynamic experiments could imitate the mechanisms of orbital blowout fracture and open globe injury,and analyze the impact conditions and influence factors.5)Retrospective investigation of open globe injury,along with finite element analysis,could help to develop strategies for the prevention of ocular injuries.6)The positioning measurement method established in the coordinate system could predict displacement of the eyeball late after orbital blowout fracture.