寰枢关节前后路侧块螺钉内固定的生物力学比较

Biomechanical comparison of the atlantoaxial anterior transarticular screw fixation

目的:比较寰枢关节前、后路侧块螺钉固定的效果,并测定其双侧、单侧侧块螺钉固定的稳定性,为临床应用提供理论依据。方法:取5具新鲜冷冻人体颈椎标本C1￣C5,用牙托粉和螺钉固定C1和C2-C5,保留C1-C2之间的活动。切断寰椎横韧带和齿状突,造成寰枢关节不稳定,每个标本依次行前路单侧、前路双侧、Margel单侧、Margel双侧侧块螺钉固定。在生物力学试验机上应用位移控制法测定6种状态下的稳定性,前屈和侧屈的位移定值为1mm,旋转角度为3°。测定完好标本、损伤后及各种内固定下在前屈、双侧侧屈和旋转状态下的刚度,比较其稳定性。结果:所有内固定组的刚度均明显高于损伤组及完好组的刚度,前路双侧侧块螺钉和后路双侧侧块螺钉固定的稳定性无明显差异。前路双侧侧块螺钉固定在前屈、左侧屈、右侧屈、旋转时的稳定性高于前、后路单侧侧块螺钉;前路单侧侧块螺钉与后路单侧侧块螺钉固定的稳定性无明显差异。结论:前、后路双侧侧块螺钉固定效果好,可单独应用于临床;而单侧侧块螺钉稳定性不足,术后需加用外固定。

Objective：To compare the biomechanical stability of C1/C2 vertebrae after anterior or posterior transarticular screw fixatlon,and to study the instrumented results by bilateral and unilateral lateral mass screw fixation.Method：5 fresh-frozen cadaveric cervical spines specimen were used for study.C1 and C2-C5 vertebrae were fixed with PMMA and screws separately,but the motion between C1 and C2 was preserved.The instability of atlas-axis was produced by cutting the odontoid,the transverse ligament on both sides of the odontoid and the tectorial membrane between C1 and C2.Lateral mass screw fixation by means of unilateral and bilateral anteriorly,unilateral and bilateral posteriorly （Margel technique） were performed in sequence according to the motheds described in the literature.The stiffness of the C1-C2 articulation of each specimen was tested under the biomechanical text platform,the text data were set up as follows：at anteflexion and lateral flexion text,the C1 vertebra displacement was lmm,and at rotation test,the range of motion was 3 degree.The stiffness of C1/C2 in all kinds of circumstances described above was measured.Result：Significantly higher stiffness values were obtained with all kinds of the fixation techniques than that with the intact and destabilized stated for all modes of testing （P〈0.01）.The bilateral anterior transarticular screws provided no significant difference stabilization compared with bilateral Magerl screws.Unilateral anterior transarticular screw had a lower stiffness compared with either bilateral anterior transarticular screws or bilateral Magerl screws.No significant difference in stiffness was found between unilateral anterior screw and unilateral posterior screw. Conclusion：The anterior bilateral mass screws can provide good stability,while unilateral anterior transarticular screw has a poor stability.