| Objective: Made AO A3.3 type burst fracture of L1,and use biomechanical method to evaluate different between whether implant in fracture vertebra or non-fracture one,and determine which method is the best and provide proof for clinical treatment for AO A3.3 type burst fracture.Methods: 3 dimensional motion test for spine: put 6 set of fresh pig thoracolumbar vertebrae packed by plastic membrane in the temperature of-20℃,in this temperature vertebrae will stay fresh and bring no effect on bone and ligament,and no change in biomechanical feature,and when the experiment is ready withdrawal the vertebrae and remain in room temperature for 12-18 hours,and inspect the surrounding muscle,fat tissue,connective tissue and remove those tissue while left ligaments,then use UHMWPE material process the vertebra of T13,L3 and also treat L1,made them experiment sample.Every sample were grouped into intact group(group A),LI complete burst fracture(AO A3.3 type)group(group B),short segment fixation group without fixation in fracture body(group C),short segment fixation group with fixation in fracture body in single side(group D),short segment fixation group with fixation in fracture body in double sides(group E),fixation in single fracture level(group F)altogether 6 groups.Every group performed 3 dimensional motion tests for each from 6 different directions,and each time gave 10 Nm effect force,the 6 motion direction were flexion in forward,extension,flexion in left and right,rotation from left and right.The whole process were monitored and measured by British software Imetrum,and collected data sorted out the records and analyzed then concluded the range of motion of the spine,which are the range of motion(ROM)between T14 and L2,as to evaluate the stability and ROM of the fixation.Toughness test: add another new set of sample(group A),withdraw 5sets of sample from 6 sets respectively as group B,C,D,E,F then use electronic multiple purpose test machine WDW3100 for compression test and calculated their toughness.Screw withdrawal force test: made mode of 4 sets of sample and group as C,D,E,F four groups,use electronic multiple purpose test machine WDW3100 for screw withdrawal force test,calculated screw withdrawal force.Results:(1)Spine three dimensional motion test:(1)compare group A and B,T14/L2 with obviously increased range of motion in three dimensional motion test,indicate burst fracture of L1 decrease in stability compare with the normal ones,so there is significant statistical different(P<0.05).(2)in group B by different fixation system(group C,D,E,F)obvious range of motion are decreased that showed the stability of group B are improved significant in statistical results in group B after fixation P<0.05).(3)compare group C and F,segments T14/L2 except no obvious(P<0.05)in range of motion in extension,there were obvious decrease in flexion forward,flexion left,flexion right,rotation left and rotation right compare between group C and F(P<0.05).suggested the stability in group C are higher in that in group F and with significant statistical different(P<0.05).(4)compare group D and C,there was obvious decrease(P<0.05)in three dimensional range of motion in segment T14/L2,indicated group D with higher stability than group C with significant statistical different(P<0.05).(5)compare between group E and group C,there was obvious decrease(P<0.05)in three dimensional range of motion in segment T14/L2,suggested group E with higher stability than group C with significant statistical different(P<0.05).(6)compare between group E and group D,there was no obvious change(P>0.05)in three dimensional range of motion in segment T14/L2,suggested no different between group D group and E no significant statistical different(P>0.05).(2)compression toughness test: Due to the nature of compression toughness test was destructive,and the samples of this experiment were limited,so there were not enough samples for statistical criteria,and only one test performed in each group.All group except group B with strong toughness.Group F tougher than C,group D tougher than C and F.group E tougher than A and was the toughest out of all groups.Screw withdrawal force test: Due to the nature of compression toughness test was destructive,and the samples of this experiment were limited,so there were not enough samples for statistical criteria,each set of sample performed screw withdrawal force test out of 4 sets of group,group F with the lowest withdrawal force,withdrawal force in group C higher than that of F.withdrawal force in Group D higher than that of C.out of all groups group E with the strongest withdrawal force.Conclusion: experiments in biomechanics show that: ① short segment fixation with single side implantation of fracture vertebra(group D)with no different to short segment fixation with double sides’ implantation of fracture vertebra(group E)and gave the optimal stability.② Short segment fixation with double sides’ implantation of fracture vertebra(group E)gave the strongest compression toughness.③ Short segment fixation with double sides’ implantation of fracture vertebra(group E)gave the strongest withdrawal force.Conclusion were made that for AO A3.3 type burst fracture in thoracolumbar vertebra the best implantation is short segment fixation with double sides’ implantation of fracture vertebra. |
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