Biomechanical Evaluation of Stand-Alone Oblique Lateral Lumbar Interbody Fusion Under 3 Different Bone Mineral Density Conditions: A Finite Element Analysis

Abstract

To evaluate the biomechanical stability of stand-alone (SA) oblique lateral interbody fusion (OLIF) under different bone mineral density conditions. The finite element model of L2-L5 was reconstructed and verified via computed tomography scan images (M0). The L4-L5 segment of SA OLIF was created based on the validation model. By changing bone mineral density, SA OLIF was established in the normal bone mineral density group (M1), osteopenia group (M2), and osteoporosis group (M3). A 500 N vertical axial preload was imposed on the superior surface of L2, and a 10 N-m moment was applied on the L2 superior surface along the radial direction to simulate 6 different physiological motions: flexion, extension, left and right lateral bending, left and right rotation. Compared with M0, the range of motion of the fusion segment was significantly reduced, and the maximum stress of the upper and lower end plates was significantly increased in all motion modes. Compared with M1, the maximum relative increases of range of motion, cephalic end-plate stress and tail end-plate stress of M2 in the L4-L5 segment were 39.1%, 9.9%, and 10.7%, and the maximum increases of the above parameters in M3 were 100%, 28.9%, and 31.6%. The maximum stress of the tail end plate of the M3 model during flexion was 54.617 MPa, which was very close to the yield stress of the lamellar bone (60 MPa). With the increase of the degree of osteoporosis, the maximum stress on the upper and lower end plates of the fusion segment increased significantly, thus increasing the potential risk of implant subsidence. SA OLIF could not provide sufficient stability for patients with osteoporosis.