| Objective: A new type of anterior cervical locking plate system and cervical lateral mass fixator were designed based on the anatomic character of Chinese people to promote the biomechanical stability in cervical spine. The biomechanics, histology and clinical application of the new cervical fixation system were investigated. Methods: New types of cervical fixation system made of titanium alloy (TC4, TJ6AL4V) were designed and manufactured on basis of literature and in accordance with the feature of the cervical spine of Chinese people, their biomechanics, histologies were studied. This study was divided into three parts. Part one: The design of anterior cervical point contact self-locking plate fixation system (PCSLP)on the basis of unicortical screw fixation and point contact plate fixation principle, and cervical lateral mass locking screw-rod system (LMLS). Part two is for biomechanical study of the new type cervical fixation systems. This part consists of two experiments. One was for evaluating spinal biomechanical stability of bovine spine construct using different implants.20 bovine cervical spine were randomly divided into four groups, which were Orion plate group, PCSLP group, LMLS group, and Cervifix rod-screw group. The stress, displacement, strength, stiffness of the spinal construct were tested under flexion, extension, left and right bending, torsion respectively. The results were statistically analyzed. Experiments two was for evaluation of pull-out behavior of different systems with locking screws or unlocking screws. 8 bovine cervical spine were randomly divided into four groups, which were anterior plate group with screws unlocked, PCSLP group, LMLS group. The screw purchases were tests for determining the initial pull-out strength. The results were statistically analyzed. Part three: Histological experiment. 16 lamb were randomly divided into control groups and experimental group anteriorly and posteriorly each. The migration of the implants and bone fusion was observed during 3-6 months follow-up. Results: The anterior cervical point contact self-locking plate fixation system is inaccordance with the feature of the cervical spine of Chinese people. The biomechanical study shows the difference of stress and displacement measurements in Orion plate group and PCSLP group under various models such as flexion, extension, lateral bending was not significant. The stress and displacement measurement in LMSRL group was less than that in Cervifix rod-screw group, but the difference was not significant. The results of pull-off testing demonstrate that differences were significant between the locking and unlocking group both anteriorly and posteriorly. Histological experiment and X-ray shows solid bony fusion in the groups with self-designed fixation system. No complications such as implant loosening or failure related to the new fixation system were noted.Conclusion: The self-designed anterior cervical plate fixation system can provide sufficient biomechanical stability to cervical spine. Cervical lateral mass locking screw-rod system is superior biomechanicaly to traditional lateral mass screw system. |
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