Biomechanical stability of a new aliform internal fixation system

English Keywords:Occipitocervical fusion  Atlantoaxial dislocation  Aliform fixation device  Biomechanical

English Abstract:

  【Abstract】 Objectives: To evaluate the biomechanical stability of a newly developed aliform internal fixation system. Methods: Six occipitocervical cadaveric specimens of fresh human were chosen, including 3 males and 3 females, aged 20-35 years old. In normal models(group N), bony structures, ligaments and articular capsules ranging from occipital protuberance to C6 were preserved, and the muscular tissue at the craniocervical junction was carefully removed. Then the transverse atlantal ligaments were cut off to make the atlantoaxial dislocation models(group UN). The Motion Analysis was used to measure the C0-C3 ROM in the group N and UN. After that, the cadavers with atlantoaxial dislocation were fixed by the aliform internal fixation system and SUMMIT system. According to different fixation methods, the cadavers were divided into 4 groups: aliform occipital plate with 11 screws fixation in group A, aliform occipital plate with 7 screws fixation in group B, aliform occipital plate with 3 screws fixation in group C, SUMMIT system fixation in group D. The biomechanical stability was compared among the 4 groups in flexion, extension, lateral flexion and rotation. Results: In the six different dimensions, the biomechanical stability of group A, B, C and D was better than that of group N and UN(P<0.05). There was no significant difference of stability among the four fixation methods in flexion, extension and lateral flexion(P>0.05). However, in left and right rotation, a significant difference of stability among the four groups was observed. There was no significant difference of biomechanical stability among group B, C and D, while the biomechanical stability of group A had significant difference with that of group B, C and D. Conclusions: Both the newly developed aliform internal fixation system and the SUMMIT system can eaually provide effective mechanical fixation strength. However, the newly developed aliform occipital plate with 11 screws fixation is better in rotation dimension.