Experimental Study On The Neotype Aliform Shape Memory Alloy Intrasegmental Fixation Instrument For The Treatment Of Lumbar Spondylolysis

Lumbar Spondylolysis is very common spine disease, with a occurrence of about 5~6% in adult population, some especially people reach up to 20%, for instance athletes, which always leads to lumbar pain. The majority of patients can be treated conservatively. However, for those who have persistent pain that is unresponsive to conservative measures, operative interventions seems to be necessary. of which bone grafting with the effective internal fixation is the universal solution. Due to some disadvantages of intersegment fixation, the technique of intrasegment fixtion have been proposed for the surgical treatment of spondylolysis in the last few years.For the past few years, there are some new methods of intrasegmental fixation. it is a improvement for three traditional methods : Buck' s technique of screw fixation or Nicol' s technique of intrasegmental wire fixation or Hefti' s technique of hook-screw fixation, all of which produce unsatisfactory results due to the its shortcomings respectively. Until 1998, the invention of two side semiring shape memory alloy intrasegmental fixation instrument indicated that some certain breakthroughs had been taken .In the dissertation,we will review the advantages ,disadvantages and application of two side half-moon shape memory alloy intrasegmental fixation instrument;in the meantime,with the advantages of memory alloy and anatomical biological feature , we attemped to develop a new intrasegmental fixation device.Materials and MethodsBasing on the data obtained from human lumbar spines in6xeransis, we developed a new intrasegmental fixation device made of NiTi shape-menory alloy. A biomechanics stability comparison between the newly-developed device and the other three traditional intrasegmental fixation methods was taken by a Spinal 3D Test Machine on fresh samples of human lumbar spines, which leads to the conclusion about the feasibility of our new device. The experiment was devided into 3 parts as follows:1. design of new intrasegmental fixation device made of NiTi shape-memory alloy basing on the anatomic data of human lumbar spines;2. the test of the new device' s mechanical property;3. the biomechanical evaluation of the new device through the biomechanical stability comparison between itself and the other three traditional intrasegmental fixation methods.Results and Conclusions1. Measuring anatomical data of lumbar spine , accord to the biomechanical and anatomical data of many lumbar spines which were acquired respectively, a new intrasegmental fixation device made of shape memory alloy was developed.2. The test of material mechanics reveals: the new device' s deformability is linearly proportional to the tension within a limit below 4mm. we choose 4mm as the rang of intrasegmental fixation deformability which was proved to produce enough pull without any impairment on the osseous tissue.3. The biomechanical experiments shows that new-developed device and the other traditional intrasegmental fixation methods mentioned above could restore the stability of the lumbar spines efficiently, with no significant statistical difference among them.4. Including intrasegmental wiring, hool-screw and Buck' s screw, all instruments we chose in our test could restore the stability of the spondylolic lumbar spines significantly, there was no significant difference between any two of them.75. The tests proved that the biomechanical capability of the newly developed shape memory alloy device are qualified to restore the stability of lumbar spines with good endurance.