Anatomical And Biomechanical Study Of The Axillary Middle Approach For The Treatment Of T2-T5 Vertebral Lesions

Objective: To evaluate whether the reconstruction of upper thoracic vertebrae via axillary midline transthorac ic approach can achieve the requirements of biomechanical stability by biomechanical analysis of three-dimens ional motion stability and load-bearing strength of upper thorac ic vertebrae in lateral and anterior internal fixation models.Methods: The C7-T6 spine and bilateral rib cage joint specimens were obtained from 12 human cadaveric bodies,and the three-dimens ional motion stability test of the complete upper thoracic vertebrae model was performed and recorded as a complete vertebral body group.Subsequently,the specimens were randomly divided into two groups,and the traditional front plate internal fixation(front internal fixation group)and the axillary line into the thoracic cavity side plate internal fixation models(lateral internal fixation group)were established,respectively,with six specimens in each group.Three-dimens ional motion test,vertical pressure test and vertical pressure failure test were performed.This study was approved by the Ethics Committee of Second Affiliated Hospital of Guangxi Medical University(approval No.2017(KY-0080)).Results:(1)The load of left vertebral body group under left/right flexion,flexion/posterior extens ion and left/right rotational motion was smaller than that of lateral internal fixation group and anterior internal fixation group(P < 0.01).The load in the front internal fixation group under left/right rotational motion was smaller than that in the lateral internal fixation group(P < 0.05).There was no significant difference between the left/right flexion and the flexion/rear extens ion between the anterior internal fixation group and the lateral internal fixation group(P > 0.05).(2)When the load reached 600 N,the vertebral body sinking displacement of the front internal fixation group was smaller than in the lateral internal fixation group [(1.39±0.20),(2.15±0.17)mm,P < 0.01].(3)There was no significant difference in the maximum intens ity load between the anterior internal fixation group and the lateral internal fixation group[(1839.70±122.45)N,(1798.65±120.21)N,P=0.571].(4)The maximum extraction strength of the internal fixation device in the lateral internal fixation group was(700.83 ± 92.98)N,and the maximum extraction strength of the front internal fixation group was(552.13 ± 103.07)N.The extraction strength of the titanium plate screws of the internal fixation group was 21.2% higher than that of the traditional front internal fixation group,and the difference was statistically significant(P <0.05).Conclusion: The lateral steel plate internal fixation through the axillary midline thoracic approach is stable in terms of three-dimensional motion,vertical load strength,and the pull-out strength of the external fixation device.This approach can be used to treat T2-T5 vertebral les ions and can be used to reconstruct the spine.The need for thoracic spine biomechanical stability.