Finite Element Analysis In The Effect Of Nucleus Pulposus Removal On Lumbar Biomechanical Characteristics

1. ObjectiveTo explore the effects exerted by the removal of nucleus pulposus in the treatment of the lumbar disc hernia on lumbar biomechanical characteristics by means of three-dimensional finite element model analysis.2. MethodsAdopting new effective CAD methods to accurately create the L4/5 segment's finite element model, respectively simulating the normal disc, the degenerated disc, the denucleated disc short after operation as well as the postoperative disc in a long run. Furthermore, to test the biomechanical index of the 4 models under the circumstances of 5 loads, ie. compression, flexion, extension, anterior shear and posterior shear.3. ResultUnder the above mentioned 5 loads, the stiffness of the degeneratedmodel has enhanced, compared with the normal one; The stiffness of the denucleated one has degraded; the stiffness of the postoperative one in a long run has an extremely rise and even surpass that of the preoperative one due to the fact that the scar tissue has filled in the intradisc cavity. The backward bulge of the degenerated model, compared with that of the normal one, will obviously lower, and the backward bulge of the denucleated model will rise again to a certain extent, while the inward bulge will occur to its inner annulus fibrous.4. ConclusionThe removal of nucleus pulposus will instabilize lumbar motion segments. Stuffing in the postoperative intradisc cavity will actually help to restore the ever lost stabilization caused by the operation's damage. Viscoelastic change will occur to the degenerated disc, reducing the backward bulge of the disc, and inward bulge will aslo occur to the denucleated disc so as to make the disc probably degrade furthermore.