The influence of anteversion of the C2 lateral mass joint on the stability of atlantoaxial joint and biomechanical evaluation of different reconstruction methods

English Keywords:Atlantoaxial joint  Lateral mass joint  Internal fixation  Stability  Biomechanics

English Abstract:

  【Abstract】 Objectives: To provide a new theoretical basis by elucidating the influence of the anteversion of the C2 Lateral mass joint on the stability of the atlantoaxial joint and the biomechanical stability of different reconstruction methods. Methods: Six male fresh human cadaveric neck specimens(C0-C3 of the occipital epiphysis) were selected. Each specimen was made into a complete state model(group A), atlantoaxial instability model by cutting the odontoid base of the specimen and causing a odontoid type Ⅱ fracture(group B), 25° forward tilt wedge osteotomy model(group C), posterior atlantoaxial pedicle screw fixation model(group D), and posterior atlantoaxial pedicle screw fixation and lateral block joint bone grafting model(group E). 1.5 N·m torque was added at flexion/extension, left/right bending and left-handed/right-handed on the spine three-dimensional motion test machine to measure the three-dimensional range of motion(ROM) under different models. Results: The ROM of the flexion/extension, left/right bending and left-handed/right-handed motion of group A were: 10.80°±0.74°/10.90°±0.54°, 9.18°±0.97°/9.06°±0.47°, 23.07°±0.27°/23.15°±0.63°; that of group B were 15.88°±0.56°/16.20°±0.48°, 17.12°±0.35°/17.27°±0.51°, 34.15°±0.38°/34.27°±0.44°; of group C were 18.93°±0.61°/20.16°±0.54°, 26.18°±1.34°/25.26°±0.71°, 40.86°±0.60°/41.16°±0.38°; of group D were 0.64°±0.19°/0.57°±0.11°, 2.01°±0.45°/1.86°±0.34°, 1.36°±0.18°/1.76°±0.13°; of group E were 0.63°±0.15°/0.51°±0.17°, 1.28°±0.86°/1.42°±0.22°, 0.50°±0.28°/0.59°±0.26°. In flexion/extension and left/ right bending, the ROM of the group C was the largest, and the differences between group C and any other group were significant (P<0.05). The ROM of group B and group C were significantly higher than that of group A(P<0.05). Compared with group A, group B and group C, the ROM of group D and group E were both significantly smaller(P<0.05), there was no significant difference between group D and group E(P>0.05). In left-handed/right-handed, group C had the largest ROM and group E the smallest. The ROM of group D and group E were significantly lower than that of group A, group B and group C(P<0.05). The difference between group D and group E was significant(P<0.05). Conclusions: The increase of the anterior tilt angle of the C2 lateral mass joint can significantly increase the ROM of the atlantoaxial vertebra, resulting in a significant decrease in the stability of flexion/extension, lateral flexion and anti-rotation. In posterior atlantoaxial pedicle screw fixation, the stability of the flexion/extension and left/right bending motions is similar to that of the posterior atlantoaxial pedicle screw fixation and lateral block joints, but the ability to restrict the atlantoaxial rotational motion is weak.