Biomechanical Comparison Of Different Supplementary Fixation Methods For Lateral Lumbar Interbody Fusion

BackgroundWith the continuous advancement of medical technology,extreme lateral interbody fusion(XLIF)has been recognized and applied by more and more spinal surgeons,and is widely used in the treatment of lumbar degenerative diseases such as lumbar spinal stenosis,discogenic low back pain,and degenerative scoliosis.The XLIF procedure does not destroy the important mechanically stable structure of the spine,nor does it enter the peritoneal cavity.Meanwhile,it has the advantages of small trauma,less intraoperative bleeding,short surgical time,low risk of infection,large fusion area and fast postoperative recovery.Although the XLIF Stand-alone fixation has been shown to provide some postoperative lumbar stability,most scholars believe that XLIF needs other supplemented fixation devices to provide sufficient stability to fix the segment,improve bone fusion rate and reduce the incidence of postoperative complications.To improve the postoperative stability of XLIF while simultaneously reducing surgical trauma,a new XLIF supplemental internal fixation method is proposed,namely "unilateral reverse facet screw".Thus,through biomechanical experimental methods,we plan to compare the differences in lumbar spine biomechanical stability of the three fixation methods of XLIF,including Stand-alone,lateral cage with unilateral reverse facet screw and lateral cage with unilateral pedicle screws,and then explore the effectiveness and reliability of XLIF combined with unilateral reverse facet screw,so as to provide a test basis for future clinical application.Methods12 fresh cadaver lumbar spine specimens were made into models of the following four states in turn:Intact(INT),XLIF Stand-alone,XLIF plus unilateral reverse facet screw(XLIF+URFS),XLIF plus unilateral pedicle screws(XLIF+UPS).And we measured in different states of each specimen the range of motion(ROM)of the L4/5 segments in 6 motion directions,including flexion,extension,left bend,right bend,left rotation and right rotation,finally made the screw axial pull-out force test.The ROM,maximum pull-out force and stiffness of each specimen were recorded for statistical comparative analysis.Results(1)In the direction of flexion,extension,left bend,right bend,left rotation and right rotation,the ROM of the L4/5 segments of the XLIF Stand-alone group,the XLIF+URFS group and the XLIF+UPS group were significantly lower than those of the INT group.(2)In the above 6 directions of motion,the ROM of the XLIF+URFS group and the XLIF+UPS group was significantly lower than those of the XLIF Stand-alone group.(3)In the direction of flexion-extension and left and right bending,the ROM of the XLIF+URFS group was significantly lower than that of the XLIF+UPS group;in the right rotation direction,it was significantly higher than that of the XLIF+UPS group;but in the left rotation direction,there was no statistical difference between the two groups.(4)In the axial pull-out force experiment,the maximum pull-out force and stiffness of the pedicle screws were higher than those of the reverse facet screws,and there was a statistical difference.ConclusionXLIF+URFS can effectively enhance the lumbar spine mechanical stability of The Stand-alone procedure.Compared with XLIF+UPS,although the stability of XLIF+URFS is relatively weaker in the direction of flexion-extension and lateral bending,the stability of XLIF+URFS is better in the direction of axial rotation.Besides,it has the advantages of less trauma,short operation time,no need to change position and increase surgical incision,which can be used as a new XLIF Stand-alone supplementary fixation method,which has certain clinical application value.