Biomechanical stability of a new integrated artificial axis

English Keywords:Prosthesis of axis  Atlantoaxial tumor  3D printing  Biomechanics

English Abstract:

  【Abstract】 Objectives: To investigate the biomechanical stability of a new integrated artificial axis. Methods: We took six fresh-frozen human cadaveric occipitocervical specimens(C0-C6), carefully removed the muscular tissue at the craniocervical junction and preserved the bony structures, ligaments and articular capsules ranging from occipital protuberance to C6 to establish the normal model(normal group). The 3D spine motion test was applied to measure the range of motion(ROM) at C2 under flexion and extension, lateral flexion and rotation conditions. After that, we resected the axis of the 6 specimens, and established integrated artificial cervical reconstruction combined with posterior occipital cervical fixation model(artificial axis group) and modified T-shaped harms cage reconstruction combined with posterior occipital and cervical fixation model(T-shaped Harms cage group) for each specimen respectively. The biomechanical stability was compared among the 3 groups in flexion, extension, lateral flexion and rotation. Statistical significance was analyzed using randomized block analysis of variance among the 3 groups, and Student-Newman-Keuls(SNK) post hoc pairwise comparisons between each two groups. Results: Biomechanical analysis of the fresh cadaveric specimens showed that of the two internal fixation system, the maximum motion was under the loads of extension. In flexion, the C2 ROM of the three groups was statistically different(P<0.05), and between the artificial axis group and the normal group there was no significant difference(P>0.05), while in modified T-shaped Harms cage group the statistical significance was greater than that of artificial axis group and normal group(P<0.05). There was no statistical difference in C2 ROM among the three groups in extension state(P>0.05). In left lateral flexion, the statistical analysis result was the same as in the flexion condition. Similarly, the C2 ROM of the three groups was statistically different in right lateral flexion(P<0.05), and there was no significant difference between artificial axis group and normal group as well as between artificial axis group and modified T-shaped Harms cage group(P>0.05), while the statistical significance of modified T-shaped Harms cage group was greater than that of normal group(P<0.05). In both left and right rotation conditions, the C2 ROM of the three groups was statistically different among the three groups(P<0.05), and the biomechanical stability of artificial axis group and modified T-shaped Harms cage group were better than that of normal group(P<0.05), whereas the statistical significance of modified T-shaped Harms cage was greater than that of artificial axis group(P<0.05). Conclusions: The reconstruction with the newly developed artificial axis prosthesis showed higher stability than T-shaped Harms cage, which provided a theoretical basis for clinical application.