Biomechanical Evaluation Of A New Titanium Alloy Artificial Lumbar Intervertebral Disc

PrefaceThe integrality of lumbar disc could be destroyed by any reason which caused low back pain. It was a very common disease in spinal surgery . The n-ative function of the lumbar disc was lost after that and affected the daily activities of human being. There were many ways to deal with this low back pain and spinal fusion was considered with a good efficacy. However, spinal fusion destroy the normal function of the lumbar spinal segment, altered biomechanics and loading at adjacent levels have begun to emerge. It causes an acceleration of the degeneration at adjacent levels. For the purpose of resolving these difficulties , artificial lumbar intervertebral disc had become a new way to deal with internal disc derangement and degenerative disc disease.The new artificial lumbar intervertebral discs in this paper were made of new titanium alloy. The mechanical characteristics of the new artificial lumbar intervertebral disc were assessed after biomechanical evaluation.Methods1. Source of the materialNew titanium alloy was gained from Institute Of Metal Research Chinese Acadamy Of Science.2. Characteristics of the new titanium alloy artificial lumbar intervertebral disc1 Transverse dimension of 32mm, radius dimension of 25mm, height of 11mm.ii D shape designed. Ellipse ball - and - socket joint designed with 6° pe-ripheric slope.iil The baseplates' exterior surfaces include six linearly arranged spikes that rise 2 mm above the outer posterior - lateral edge of the device. Both of the posterior central portion of the baseplate are domed to a height of 1.5 mm.3. Processing methodsThe new titanium alloy artificial lumbar intervertebral discs were made by accurate method.4. Biomechanical evaluationThe compressive stiffness, torsional stiffness, fatigue strength of the prosthesis were evaluated by the material testing machine.ResultsThe new artificial lumbar intervertebral disc has functions of flexion, extension, lateral bending, passing through the mechanical tests with low stiffness, torsional stiffness is 388. 54Nm/deg, no damage appeared after 1 10 fatigue strength test.DiscussionZdeblick considered that there were three types of pathologic status in intervertebral disc which caused low back pain. Including internal disc derangement (IDD) , degenerative disc disease ( DDD) and segmental instability. They caused low back pain in clinic and affected the daily activities of human being. Although rebuilt the stability of vertebral column, relieved low back pain, spinal fusion with many complications also gained a bad prostecdtive efficacy. Artificial disc replacement ( ADR) rebuilds the important physical function of intervertebral disc, including recovering intervertebral height, stress conduction and distribution and keeping the limited motion of intervertebral joint. In addition, the degenerative intervertebral disc with injury and inflammation can be removed with artificial disc replacement then the source of autoimmunity and substance inducing inflammation were decreased for alleviating pain. So ADR has been asa effective to treat internal disc derangement (IDD) and degeneration disc disease (DDD).There are three types of artificial lumbar intervertebral disc base on the difference of the material: non — metal, metal on metal and a combined prosthesis. Prosthesis made of metal has a better fatigue strength, however, the higher modulus of elasticity is not fit the bone of the body, this lead to many complications such as prosthesis subsidence.The results of biomechanical test demonstrates that the new artificial lumbar intervertebral disc has the characteristics of lower compressive stiffness, higher fatigue strength and fit human being body better.ConclusionThe mechanical characteristics of the new artificial lumbar intervertebral disc are similar with the normal human lumbar disc.