Abstract:

Objective　To establish an effective L3~5 three-dimensional finite element model, and study the biomechanical attributes of the anatomical nano-hydroxyapatite / polyamide 66 cage in XLIF/OLIF operation.　Methods　We established the model of normal lumbar spine( L3~5) in order to simulate the XLIF/OLIF operation process by assembling a new anatomic cage and a bullet- liked cage, and the assignment model was imported into software to obtain the final finite element model. Pre-load with axial compression of 400 N and 8 Nm torque was imposed on the model, which caused motion of flexion, extension, bending and rotation of the model. the maximum stress, stress distribution of the two kinds of cage and the ROM of the L4~L5 were analyzed.　Results　Under 6 different operating conditions, the maximum stress of the bullet-liked cage was 134.83, 79.17, 71.31, 114.96, 76.85, 78.77 MPa, and the maximum stress of the anatomic cage was 56.91, 61.78, 35.82, 52.28, 31.76, and 32.45 MPa, respectively. The stress distribution of anatomic cage was smaller and more dispersed than that of the bullet-liked cage. The ROM of L4~L5 in the two groups was significantly less than that of the normal persons，and the ROM of L4~L5 in anatomic cage group was less than that of the bullet-liked cage group.　Conclusions 　The application of the new anatomic nano-hydroxyapatite / polyamide 66 cage in minimally invasive XLIF/OLIF operation can reduce the maximum stress, circumvent the stress concentration and reduce the activity of vertebral body, proving that it has better mechanical properties.

Key words: Anatomic cage, Nano-hydroxyapatite/polyamide 66, XLIF/OLIF, Finite element