Biomechanics of Cage for Stand-alone Oblique Lumbar Interbody Fusion

To analyze the biomechanical properties of stand-alone oblique lumbar interbody fusion (SA OLIF) cage using finite element analysis.

Established the L3-5 finite element model to study the SA OLIF from the stability and the stress of the cage.

SA OLIF is less invasive, but whether SA OLIF is stable and increases the risk of cage subsidence remains controversial.

The L3-5 CT image data of a healthy adult male volunteer was selected. First, calculate the range of motion (ROM) of L4-5 under flexion, extension, left bending, right bending, left rotation, and right rotation.Then, the L4-5 intervertebral discs were excised, and the cage was implanted to establish a SA OLIF model. On this basis, bilateral pedicle screw (BPS) fixation was added to establish the BPS model. Analyze the ROM of L4-5 and the maximum stress of cage under all motion patterns.

The ROM of L4-5 segments in the validation model was basically consistent with previous reports. The range of activity of BPS in each working condition was significantly lower than that of Normal and SA. Compared with BPS, Normal and SA increase by 925.9%, 1034.6%, 1107.4%, , and 1146.2% in flexion and extension, respectively. SA had higher range of activity than normal in flexion and extension, but lower in left bending, right bending, left rotation, and right rotation. The maximum stress of SA cage was greater than that of BPS under all working conditions, and increased by 363.2% and 1899.4% in flexion and extension, respectively, compared with BPS.

SA OLIF is relatively poor in maintaining the stability of the fusion segment, and there is a higher risk of cage subsidence in the later stage.