Design And Biomechanical Study Of Anterior Cervical-Adjustable Fusion Fixator

Objective: In order to improve the integral stability of the plate, screw, vertebra and fusion in anterior cervical approach, the anterior cervical-adjustable fusion fixator (AC-AFF) was designed according to iconographic measurement of the endplate gradient and anterior column height on cervical vertebral body. The biomechanical characteristics of AC-AFF was evaluated.Methods: AC-AFFs for Chinese human being was designed and their biomechanics were studied. This study was divided into three parts. Part one: Iconographic measurement. For the sake of providing the rational data for designing the AC-AFF, 160 cases of normal persons and 60 cases of cervical spondylotic myelopathy(CSM) were included in this part. The endplate gradients and anterior cervical column heights of all above cases were obtained by use of Iconogiaphic measurement. Part two: The design of AC-AFF. On base of iconographic measurement and literature, the draw and the shape of AC-AFF were designed. The material and functional characteristic of AC-AFF were also described. Part three is for biomechanical study of AC-AFF. Thirty-two bovine cervical specimens were randomly divided into four groups, wnich were AC-AFF group, iliac graft (AI group), titanium mesh (AT group)with supplemented anterior cervical plate and control group. The displacement, strain, strength, stiffness and ultimate strength of each flexion, extension and lateral bending respectively. The results were group were measured under the states of vertical compression, statistically analyzed.Results: The endplate gradient of cervical vertebral bodies increases gradually, and the anterior column height increases with age. The upper endplate gradient after operation in CSM is approximately zero degree (0.06?.02) and the lower endplate gradient is six degree(6.07?.90). The anterior column height ranges from 53.95mm to 60.35mm.Therefore,the gradient of AC-AFF's upper surface should be six degree, which can be fit for the lower endplate gradient. The adjustable length of AC-AFF should range from 41.50mm to 47.90mm. According to the result of biomechanical test for AC-AFF, the strain range of the AC-AFF group is less than that of under the states of vertical compression and fltxion. The displacement of the AC-AFF group is less than those of the other two experimental groups when the load from different directions forced the cervical specimens. The rigidity of all experimental groups is more significantly increased than that of the control group. But the rigidity of the AC-AFF group is the highest. Ultimatestrength test shows the crippling load in the AC-AFF group is higher than that of the AI group and AT group.Conclusions: AC-AFF for Chinese human being has an ideal adjustable ability and rational biomechanical stability. It can be used alone during the anterior cervical approach and its construct has an effect biomechanical stability.