The Ultimate Biomechanical Study On Bioactive Artificial Vertebrae Of Nano-Hydroxyapatite And Polymide66 And The Treatment For The Thoracolumbar Burst Fracture With The Bioactive Artificial Vertebrae

The artificial vertebral body had been applied to the treatments of spinal tumor,tuberculosis,fracture,and infection,with better effects.The materials used for the artificial vertebral body were porcelain,alloy, variant bone, and composite.But each of them had its own advantages and disadvantages. Tissue bone engineering has provided composite material for vertebral replacement with follow-up stablity after surgery as well as permanent bone synthesis with vertebrae . Professor Yu-bao LI designed and develeped a biomimetric composite of nano-hydroxyapatite and polyamide (PA66). Analytical and testing results indicated that n-HA distributes homogeneously in polyamide matrix. Hydrothermally needle-shape apatite crystals are similar to bone in morphology, composition, crystal structure and crystallinity synthesized, nanograde. showed promising prospect for tissue bone engineering. This study have two separate parts.(一)The Ultimate Biomechanical study on bioactive artificial vertebrae of nano-hydroxyapatite and polymide66(二)The treatment for the thoracolumbar burst fracture with the bioactive artificial vertebrae of nano-hydroxyapatite and polymide66【OBJECTIVE】: The purpose of this study was to evaluate the ultimate biomechanics of the bioactive artificial vertebrae of n-HA/PA66 and the clinical study of reconstructing the thoracolumbar burst fracture, examing the ultimate loading and displacement of bioactive artificial vertebrae in collum, thoraco,lumbar; analyzing biomechanical capability of bioactive artificial vertebrae and its function in the thoracolumbar burst fracture, and its impact in clinical practice, to provided referenced data for the advance clinical study of this bioactive material.【METHODS】: (1)Human spine specimens were divided into three parts: collum, thoraco and lumbar, with each part having its own matched pair. The matched pairs were randomly allocated into four groups which were control group(IS) , iliac bone group(IBG) , titanium-net group (TI) ,and the bioactive artificial vertebrae group(AVB). The control group was tested by superposing the matched vertebral bodys top and bottom, while the IBG, TI and AVB were tested by setting iliac bone, titanium-net and bioactive artificial vertebrae in the midsetion of the matched vertebral bodys and compressing them in axial direction respectively. To-be-tested experimental groups were set on the electronic universal material testing machine to test the load displacement, taking down the curve of the load displacement. When the vertebrae began to dent or fracture compressed, the load displacement curve came to the highest point, and the load of the vertebrae began to drop. Information of the load was taken by computer data collection system, testing the highest load and displacement respectively by analyzing the test accordingly.(2)From December 2003 to Febrary 2006, 36patients were treated with surgery through anterior approach for decompression and implanted with the bioactive artificial vertebrae of n-HA/PA66 composite to reconstruct the structure of thoraco-lumbar. To investigate the efficacy using the bioactive artificial vertebrae to restore the height and architecture of the burst thoraco-lumbar fracture.【RESULTS】: (1) The ultimate load and displacement of the intact specimen is the highest compared with iliac bone group , titanium-net group, and the bioactive artificial vertebrae group, while IBG is the lowest, only 26%-31% of the control group. The bioactive artificial vertebrae group can protect vertebrae better than others, and it has very good load capacity as well as titanium-net does.(2)All the patients were successfuly followed-up for an average of 8 months, ranging from 6 to 21 months. The bioactive artificial vertebrae of n-HA/PA66 composite are fused with the receptor bone in 3~4 months after operation. The neurological function of the patients were restored partially or completely. The thoraco-lumbar spine were stable during physical examination and the height of thoraco-lumbar restored did not lose during follow-up.【CONCLUSIONS】:(1)Our results show the bioactive artificial vertebrae of n-HA/PA66 has good biological activity, load capacity of axial compress as well as vertebrae supporting capacity with excellent biomechanic performance, which can be an excellent material for vertebral replacement with promising prospect for application.(2)Our results show the bioactive artificial vertebrae of n-HA/PA66 can restore the height and structure of the burst fracture of thoraco-lumbar and reconstruct the stucture of the thoracolumbar vertebrae effectively.