Finite Element Analysis On Stress Distribution Change Of The Degenerative Lumbar Disc

Objectives: Analysis the stress distribution change of the degenerative disc under5different physiological loadings.Methods：A three-dimensional finite element model of the normal human lumbarspine was developed. Three spinal segments (L3–S1) were used to investigate andmodified to simulate a mildly and moderately degenerated disc at the L4–L5lumbarlevel. The3D finite element models were imported into Ansys and analyzed.500Npressure was loaded on the upper surface of L3,10Nm moments was loaded to simulatelumbar axial compression, anteflexion, extension, lateral bending and rotation.Measuring the stress distributions of the degenerative disc and the normal one andanalysis the change.Results: Under the axial compression the healthy disc stress is concentrated nearthe pedicle, and the largest compressive force of the partition is29.649N. Under thebending loading the disc stress is concentrated in the bending side and the largestcompressive force of the partition is59.514N. The stress gradually reduced to thecontralateral, and the tensile force is32.686N. After the disc degenerated, the stressdistribution has changed. The force on the nucleus pulposus reduced from45.17~55.308N to5.471~8.046N and at the same time the force on the fibrous ringincreased. The force on the inner layer increased from80.379N~95.923N to98.898N~120.557N, the middle layer force increased from107.160N~140.983N to118.549N~156.827N and the outer layer force increased from160.872N~204.867N to169.302N~216.298N.Conclusions: After the disc degenerated, the stress distribution has changed.Though the total stress is almost the same, the stress on the nucleus pulposussignificantly reduced and the stress on the fibrous ring increased relatively, especiallyon the inner and the middle ones. The stress distribution of disc is uneven and the fibrous ring is easier to be damaged. This study will help clinicians understand theinitiation and progression of the degenerative disc disease and will assist to guide thetreatment of the disease.