Evaluation of Testing Method of the Posterior Spinal Fixator

• Main Authors: Chen-Kai Liao, 廖振凱
• Other Authors: Cheng-Kung Cheng
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/57230709839441605641

碩士 === 國立陽明大學 === 醫學工程研究所 === 89 === Regarding to the back pain problem, it usually undergoes spinal fusion surgery when the spine results in the occurrence of instability. Spinal fusion is used to help to increase spinal stability by spinal fixators. Spinal fixators can provide following functions including to support spine, maintain correction, prevent progression of deformity, alleviate or eliminate pain. Nowadays in Taiwan, there are no complete and unique test standards to evaluate different kinds of spinal fixators so that these spinal fixators were tested under different test standards. As the result, clinicians are difficult to compare present spinal fixators with each other under the same test standards. Therefore, it is necessary to make a complete and unique standard to quantify the biomechanical properties of the spinal fixators in Taiwan whatever the spinal fixators were made by compatriots or imported from other countries. The results of tests can be made comparisons with different kinds of spinal fixators and justified the qualities and reliability. The purpose of this study is to establish the test standards of spinal fixators. The method of this study is based on the standard of “American Society for Testing and Materials, ASTM, F1717-96”. We modified some parts unsuitable and replenished with pullout test. The followings are the test items: axial compression, compression bending, tension bending, torsion, pullout and fatigue test. After establishing the testing standards, we started to test the spinal fixator according to them. The spinal fixator this study used was CDH (Cortrel Dubbouset Horizon) made by Metronic Sofamor Danek, USA. The ultra high molecular weight polyethylene (UHMWPE) was conducted to imitate spinal vertebra. In the static biomechanical tests, all specimens had fractures in plugs except torsional test and pullout test. There were fractures in the middle part of synthetic bones in pullout test. In fatigue test, there was no damage under the load level of 50 % compressive bending yield load. It then reached 1,000,000 cycles without any destruction. Under the 75 % and 100 % compressive bending yield loads, the rod or plug fractured. In the experiments, the weakest point of CDH was plug that was also the point of stress concentration. This study has established a complete test standard procedure for spinal fixators. According to the testing standard, this study performed biomechanical testings in CDH and then provided some experimental results for future comparison with other kinds of spinal fixators.