Biomechanical Evaluation And Analysis Between Thoraclumbar Fractures After Anterior Or Posterior Internal Fixation By Means Of Finite Element Method

【Objective】To elvate and compare the biomechanical staility among normalthoroclumbar vertra, thoraclumbar fracture after anterior or posterior interior fixation.To analysize the cause of secondary kyphosis after operation of thoraclumbarfracture with internal fixation device.【Methods】A 30-year old healthy man's thoraclumbar vertra is scaned by CT, madea segment and unit division to every level. Then, put the datum into computer, tobuilt a 3-D finite element model and combine internal device finite element modelinto the anterior or middle-column fracture model which is compiled by computerwith SUPPER-SAP software; load the model with normal body weight fromdifferent directions, namely vertical , anteflexion, retroflexion, side flexion, axialrotation. Calculate the model and obtain datum.Analysize the datum with statistics.【Result】(1)Under the anterior column thoraclumbar fracture conditions: thestability of anterior fixation(AF) is better than that of posterior fixation(PF) invertical, left side flexion, axial rotation, violence(P<0.01),AF is similar to PF inanteflexion(P>0.01), left side flexion. (2) Under the middle column thoraclumbarfracture conditions: the stability of PF is better than that of AF in vertical,retroflexion, left, right side flexion, violence(P<0.01), PF is similar to AF in axialrotation(P>0.01), PF is less than AF in anteflexion(P<0.01). (3) Under theanterior-middle column thoraclumbar fracture conditions: the stability of AF is betterthan that of PF in vertical, anteflexion ,left side flexion, axial rotation,violence(P<0.01), AF is less than PF in retroflexion, right side flexion (P<0.01). (4)Under all thoraclumbar fracture conditions: the stability of normal vertra is betterthan that of AF and PF in all direction(P<0.01).【Conclusion】(1) Biomechanical stability after all internal fixation operation is lessthan that of normal thoraculmbar spine.It can lead to the secondary kyphosis afteroperation of thoraclumbar fracture with internal fixation device. (2) The selection ofinternal fixation system according to biomechanical opinion:　Ⅰ　The anteriorfixation is slected under the anterior column thoraclumbar fracture conditions;　Ⅱ　The posterior internal fixation device is selected the middle column thoraclumbarfracture conditions;　ⅢThe anterior fixation is slected under all thoraclumbarfracture conditions.