[Three-dimensional finite element analysis of lumbar disc herniation under different body positions]

Objective: To campare biomechanical effects of different postural compression techniques on three-dimensional model of lumbar disc herniation (LDH) by finite element analysis.

Methods: Lumbar CT image of a 48-year-old female patient with LDH (heighted 163 cm, weighted 53 kg) was collected. Mimics 20.0, Geomagic Studio, Solidwords and other software were used to establish three-dimensional finite element model of LDH on L_4,5 segments. Compression techniques under horizontal position, 30° forward bending and 10° backward extension were simulated respectively. After applying the pressure, the effects of compression techniques under different positions on stress, strain and displacement of various tissues of intervertebral disc and nerve root were observed.

Results: L4, 5 segment finite element model was successfully established, and the model was validated. When compression manipulation was performed on the horizontal position, 30° flexion and 10° extension, the annular stress were 0.732, 5.929, 1.286 MPa, the nucleus pulposus stress were 0.190, 1.527, 0.295 MPa, and the annular strain were 0.097, 0.922 and 0.424, the strain sizes of nucleus pulposus were 0.153, 1.222 and 0.282, respectively. The overall displacement distance of intervertebral disc on Y direction were -3.707, -18.990, -4.171 mm, and displacement distance of nerve root on Y direction were +7.836, +5.341, +3.859 mm, respectively. The relative displacement distances of nerve root and intervertebral disc on Y direction were 11.543, 24.331 and 8.030 mm, respectively.

Conclusion: Compression manipulation could make herniated intervertebral disc produce contraction and retraction trend, by increasing the distance between herniated intervertebral disc and nerve root, to reduce symptoms of nerve compression, to achieve purpose of treatment for patients with LDH, in which the compression manipulation is more effective when the forward flexion is 30°.