Biomechanical Evaluation Of Oblique Lateral Interbody Fusion

Objective:To investigate and compare the biomechanical stability of oblique lateral interbody fusion without or with various supplemental internal fixation methods by biomechanical experiments of calf cadaver specimens,which provided reference and biomechanical basis for the application of this technique in China.Methods:Seven fresh calf lumbar spine specimens were collected and four models were prepared according to the following groups: intact group(INT),OLIF Stand-alone group(Stand-alone),OLIF plus unilateral pedicle screw group(OLIF+UPS),OLIF plus bilateral pedicle screws(OLIF+BPS).Nondestructive flexibility tests in six directions of flexion,extension,lateral bending and axial rotation were performed in sequence using the spine multi-degree of freedom biomechanical testing machine.Load of 7.5 Nm maximum were applied with a compressive preload of 300 N.In each loading direction,3 preconditioning cycles were applied to eliminate the creep effect.The displacement sensor automatically collects the L3–4 angular range of motion(ROM)during the third loading.ROM and stiffness were recorded and compared.Results:In this study,the INT,OLIF Stand-alone,OLIF+UPS and OLIF+BPS models of calf lumbar cadaver specimens was successfully constructed in vitro,and compared the L3/4 motion segment stability and stiffness.Compared with the INT group,the ROM of the Stand-alone group and the OLIF+UPS group decreased during flexionextension and lateral bending,and the stiffness increased(P<0.05).There was no significant difference in ROM and stiffness during axial rotation(P>0.05).Compared with the INT group,the ROM of the Stand-alone group decreased by 61%,36%,53%,and 55% during the flexion,extension,right and left bending,respectively.Compared with the INT group,the ROM of the OLIF+UPS group decreased by 65%,46%,64%,63% during the flexion,extension,right and left bending,respectively.Compared with the INT group,the ROM of the OLIF+BPS group decreased in all directions(P<0.05).OLIF+BPS group reduced ROM by 71% in flexion,51% in extension,71% in right bending,70% in left bending,26% in right rotation,and 16% in left rotation relative to intact specimens.The OLIF+UPS group provided a decrease in ROM and increase stiffness compared with that of the Stand-alone group during flexion and lateral bending(P<0.05).Compared with the Stand-alone group,the OLIF+BPS group ROM decreased during flexion and extension,lateral bending,and right side rotation(P<0.05),and the stiffness increased during flexion,lateral bending,and right rotation.Compared with the OLIF+UPS group,the OLIF+BPS group ROM decreased in the extension,lateral bend and right side rotation,and the stiffness increased(P<0.05).Conclusions : The OLIF Stand-alone procedure provides acceptable immediate stability,especially in flexion-extension and lateral bending.Adding UPS to the OLIF Stand-alone to further reduce the stiffness and ROM during the flexion and lateral bending motion.Although Stand-alone and OLIF+UPS provide satisfactory stability in flexion-extension and lateral bending motions,neither of these procedures can effectively limit rotation motion.OLIF+BPS can significantly reduce ROM during all directions of motion relative to intact specimens,and increase the stiffness of the motion segment during flexion-extension and lateral bending.In the comparison of the three surgical procedures,OLIF+BPS is the most rigid and the greatest stability among the constructs.