| [Background]The lumbar fusion is one of the most common operation methods to treat degenerative lumbar disease and lumbar instability,and its purpose is to get segmental stability through fusion.Cragg was the first to propose the concept of axial lumbosacral interbody fusion(AxiaLIF),and proved the feasibility and safety of the operation.Compared with the traditional anterior or posterior intervertebral fusion surgery,the AxiaLIF via the pre-sacral space to complete the surgery,don't stripping the tissue and muscle,and don't break the articular process,annulus and ligaments,and minimize the damage to the structure of spine,so there are some biomechanics advantage in theory.The biomechanics study of AxiaLIF confirmed that it can provide reliable stability for fixed section.But the control of rotation is worse in all activities,and Supplemented with posterior pedicle or articular screw could obtain better stability.About the clinical application,the domestic and foreign researchers have successively completed thousands of cases of AxiaLIF,unanimously affirmed its clinical characteristics of minimally invasive,safe and effective.But at the same time,it is generally believed that combined with the posterior fixation can obtain better fusion effect,which not only increasing the complexity of the operation,extending the operation time,increasing the damage of the patients,but also increasing the risk of surgery and the incidence of complications.To this end,we envision to fix two axial screws in the anterior and middle column of the L5 and SI vertebral bodies respectively,which could increase the stability between the two vertebral bodies,and also could avoid the additional damage by the posterior pedicle or articular screws.[Objective]To discuss the feasibility of bi-axial lumbosacral interbody fusion,and provide theory support for the improvement of the operation.[Methods]Fifteen fresh adult lumbosacral specimen were selected,and immediately measure the relevant anatomical data about the Bi-axiaLIF.And fifty adult lumbosacral CT were selected,measured the same data based an the three-dimensional reconstruction technique to verify its security and to provide data guidance for the design of screws.Three surgical finite element models were established respectively:? the traditional AxiaLIF combined with double articular screws fixation;the AxiaLIF that fixed the middle column combined with double articular screws fixation;?the bi-axial lumbosacral interbody fusion.Under the flexion,extension,right bending,left rotating to simulate different activities,and Analyzing the biomechanical characteristics of the three kinds of operation models and the normal model.[Results]The sagittal diameter and transverse diameter of L5/S1 intervertebral disc were 32.1±2.25mm and 43.5±2.84mm respectively;the sagittal diameter and transverse diameter of nucleus were 22.5±1.31mm and 32.3±2.10mm respectively.In the specimen and imaging anatomy study,the maximum distance from the sacrum to the line,which simulated the operation approach of the anterior column fusion screw,was 16.93±3.02mm and 17.06±5.80mm respectively.In the finite element analysis,compared with the two group of single axial fusion combined with articular screws fixation,there are no difference about the stability in the Bi-axiaLIF model under the flexion,extension,lateral bending and rotation.And the von Mises press of the screws,the bone and the L4/5 intervertebral disc in the Bi-axiaLIF model show a less stress concentration,which could effectively reduce the risk of screw fracture,loosening,vertebral subsiding and the degeneration of the adjacent segment.[Conclusion]The pathway of the Bi-axiaLIF has a certain security,and the method also has good biomechanical properties. |
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