Effects Of Lumbar Rotated And Localized Manipulation On Inner Stress And Displacement Of Degenerative Lumbar Disc

Objective: 1. To explore effects of lumbar rotated and localized manipulation on inner stress and displacement of degenerative lumbar intervertebral disc. 2. To explore the mechanism, rationality and security of Lumbar rotated and localized manipulation. 3. To compare the effects of Lumbar rotated and localized manipulation between normal and degenerative lumbar disc and between normal and degenerative motion unit of lumbar.Method:1. Model establishing: one intact fresh young man cadaveric atlas was scanned with CT with 1mm interval through its lumbar vertebrae. Then, the jpg-format data of CT were inputted into computer and were utilized to establish the three-dimensional FEM by using software Mimics. Then the FEM was modified by Freeform system. The FEM was definite as followed: fiber, capsule and ligament only carry the strain; Annulus fibrous of intervertebral disc was viewed as compound structure which was composed of homocentric fiber intercrossing 120° and embedded in the matrix. Trabecular bone and lumbar intervertebral disc were delinked as muti-bore elasticity material. Parameter of every material mechanics was definited such as elastic modulus and poisson's ratio, et al. 2.Decomposing and loading condition of manipulation: lumbar rotated and Localized manipulation made lumbar move in three directions: lateral bending, flexion, rotation, Respective definite as rotating around coordinate axis: Z, X, Y. Max-angle of bending and rotation was selected and according to the levels of flexion angle, manipulation was ranked three levels: A, B, C. During manipulation, pressure from half of superior body, rotating force from manipulation practicer and pushing force from thumb on the spinousprocess acted on the lumbar vertebrae together: The weight of the half of body above was 30kg and its pressure was 300N; the rotated movement was 15Nm; the pushing movement measured was 3Nm. The sudden rotating time of manipulation was 0.25 second. The explicit loading condition as follow (rotating toward right and unit of L4-L5 were selected as subject):1. Z bending 6°2. X flexion C-level: 9° B-level: 6° A-level: 3°3. Y clockwise rotation 2°4. Y pressure 300N5. Bottom of L5 was fixed6. Clockwise movement of 15Nm was load on the top of L47. Movement toward left-anterior of 3Nm was load on the spinous process.8. Sudden time: 0.25 second Analyze: using software Ansys 7.0 Result:1. Characteristic of stress, displacement and distortion of lumbar disc in C-level. Three of them increase gradually to max during the manipulation. The end-stress distribution: The end-stress descends from right-anterior-lateral side, which stress was max and manifest pressure mainly, to left-posterior-lateral side, which stress was min and manifests strain up and down in form of arc. The bigger main-stress was pressure and strain toward posterior-inner in the right-posterior-lateral region. The end displacement of lumbar intervertebral disc, which direction was same to the stress, descends from right-anterior-lateral side to left-posterior-lateral side in form of layer. The right-posterior region's displacement was more than the left posterior's in the same level, which was same to the end-distortion. The main distortion was compression and expansion.2. Comparison of stress and displacement in three levels. Comparing three levels, the same stress and displacement: the max-stress descends from right-anterior-lateral side in form of arc; the end displacement of lumbar interveterbral disc descends from right-anterior-lateral side which displacement was max to left-posterior-lateral side in form of layer. The different stress and displacement: with the increase of flexion angle, the pressure in nucleus pulpous and the scope of the distribution around the disc and stress on right-posterior-lateral side and mid-posterior region increase. On the contrary, stress on left-posterior-lateral side decreases. The displacement of two posterior-lateralside was nearly same under A and B levels, but the displacement of the rotation side was more than the opposite side's result from the protrusion distortion, especially in C level.3. Comparison of characteristic of stress and displacement of degenerated and normal lumbar disc in C-level. The result of degenerated disc was much different from the normal disc's when stimulating the manipulation: to normal disc, the stress surround the nucleus pulpous from little to much. The max stress distributes on anterior side and the posterior side, the former was mainly pressure and the latter strain. The stress on rotated side was smaller than opposite side. To degenerated disc, the stress distribution in form of arc descends from anterior-lateral side of rotation which stress was max to opposite angle which stress was min. In addition, there was a max stress region in posterior-lateral side of rotation too. Taking displacement into account, the max displacement of normal disc was on anterior region which distortion was dominated by compression, followed by expansion at the same time, and posterior-lateral region of opposite rotation side. There was same rotated displacement on two posterior-lateral sides, which protrusion toward back was not obvious. Differently, the max displacement of degenerate disc was on the anterior-lateral region of rotated side which distortion was mainly compress. The min displacement of degenerated disc distributes on the posterior-lateral region of opposite rotated side. Two posterior-lateral sides' displacement was different because the strain of left was smaller than the right's.4. Characteristic of stress and displacement of lumbar unit in C-level. Accompanying by manipulation, the displacement and stress of the lumbar unit ascend gradually. The end max-stress distributes in isthmus, pedicle of vertebral, super articular facet; the end max-stress of lumbar disc distributes in the anterior-lateral side and the stress of the right-posterior-lateral side was more than the opposite side's. The max-displacement was on the top of the super articular facet; the displacement of the left articular facet was much more than the right articular facet, which was same to the intervertebral foramen. The right-anterior-lateral disc protrudes toward posterior-inner.5. Comparison of characteristic of stress and displacement of degenerated and motion of unit of normal lumbar spine in three levels. To normal motion unit of lumbar spine, the earliest change of stress occurs on endplates, then extends toward all interveterbral body gradually, at last the max stress concentrate on superior of L5 endplates, inferior endplates of L4 and disc. There isn't nearly any stress on the spinal posterior structure. Interveterbral foramens of two sides become bigger, which the rightwas little more than the left, because of the displacement of articular facet. There was not obvious displacement and protrusion toward posterior and just little compress and expansion on disc.Conclusion:1. The manipulation cannot make the protruded disc come back because there was not only no main stress toward center of disc but also protrusion distort toward back in posterior-lateral region of rotatory side. 2.Because except for the protrusion distort of disc, the displacement result from rotation of two posterior-lateral sides was same, the possible mechanism of manipulation was that nerve roots and disc was separated by it completely or incompletely. 3.The more flexion angle is, the more possibility of rupture of disc is. In addition, because the displacement result from rotation of two posterior-lateral sides was same and the intervertebral foramen of opposite rotatory side turn bigger than rotatory side's, it was safer and more rational for rotation manipulation in a small flexion angle toward the healthy side. 4.The effects of rotatory manipulation on normal and degenerated lumbar disc was different, the same to normal and degenerated lumbar unit. It was noticeable that lumbar rotatory and localized manipulation shouldn't be applied to those patients with spondylolisthesis or with complete or partial laminectomy of vertebral arch because, to degenerated disc, the stress mainly concentrated in spinal posterior structure.