Anatomical And Biomechanical Study For Design Of Atlantoaxial Lateral Mass Intervertebral Fusion Cage

Dislocation and instability of atlantoaxial complex is common in spinal surgery,and its surgical management usually involves fixation and fusion of the atlantoaixal complex using a posterior surgical approach to the cervical spine.Despite its success,there are drawbacks associated with the posterior surgical approach,such as high demand of the graft.And there is unreasonable effectiveness of biomechanical result in fusion rates because of the tension from the posterior for the graft.The final purpose of the atlantoaxial fusion is to achieve stability for the lateral mass joint of atlantoaxial,therefore,the reasonable fusion should be in the articulation of the lateral mass.With this study,we intend to design an atlantoaxial lateral mass intervertebral fusion cage,and expect to treat dislocation and instability of atlantoaxial complex with it.Partâ… Anatomical and radiological study for design atlantoaxial lateral mass intervertebral fusion cageThirty-five sets of adult dry atlas and axis specimens and fifty sets of adult CT of cervical spine were measured.The results manifested that the design of atlantoaxial lateral mass intervertebral fusion cage is feasible on morphology and the parameters of its components are in certain ranges.Partâ…¡Design and manufacture atlantoaxial lateral mass intervertebral fusion cageThe demand in design of atlantoaxial lateral mass intervertebral fusion cage referred to the design of subcervical interbody fusion,and the configuration fit with the normal anatomy of atlantoaxial lateral mass.The cage was a flat hollow polyhedron which made of titanium alloy,and it was consisted of two support segments.The former segment was resembling a cone,and the latter has the approximate shape of a cube.After implantation the intervertebral of atlantoaxial lateral mass,it can limit the motion of the atlantoaxial lateral mass joint and treat the atlantoaxial dislocation or instability.Partâ…¢The biomechanics of atlantoaxial lateral mass intervertebral fusion cageSix human cervical specimens C0-C4,according to a random sequence,were loaded nondestructively with 1.5Nm in the unconstrained testing apparatus and specimens were respectively instrumented with each of the following fixation techniques:intact, transverse-alar-apical ligament disruption,transarticular screws and Gallie fixation(TA+Gallie),isthmic screws in the axis combined with the atlas laminar hook fixation(C2+hook),lateral mass screws in the atlas combined with isthmic screws in the axis(C1+C2),atlantoaxial lateral mass intervertebral fusion cage and lateral mass screws in the atlas combined with isthmic screws in the axis(C1+C2+cage),then biomechanical data at the level of C1-C2 were measured.The data indicated that C1+C2+cage provides the good stability in biomechanically.ConclusionsThe design of atlantoaxial lateral mass intervertebral fusion cage is feasible on morphology.The cage can be inserted using posterior approach.Biomechanically,the preliminary results showed that it was effective in strengthening the rotational stability of the atlantoaxial fixation when combined with C1+C2,and also can increase two fusion points to treat the instability of atlantoaxial complex.