Department of Orthopaedic Surgery, 2nd Affiliated Hospital of Zhejiang University College of Medicine, Hangzhou, Zhejiang Province, China.
Clin Orthop Relat Res. 2012 Jul;470(7):2021-8. doi: 10.1007/s11999-012-2389-1. Epub 2012 May 15.
Anterior screw fixation has been widely adopted for the treatment of type II dens fractures. However, there is still controversy regarding whether one- or two-screw fixation is more appropriate.
QUESTIONS/PURPOSES: We addressed three questions: (1) Do one- and two-screw fixation techniques differ regarding shear stiffness and rotational stiffness? (2) Can shear stiffness and rotational stiffness after screw fixation be restored to normal? (3) Does stiffness after screw fixation correlate with bone mineral density (BMD)?
We randomly assigned 14 fresh axes into two groups (seven axes each): one receiving one-screw fixation and another receiving two-screw fixation. Shear and torsional stiffness were measured using a nondestructive low-load test in six directions. A transverse osteotomy then was created at the base of the dens and fixed using one or two screws. Shear and torsional stiffness were tested again under the same testing conditions.
Mean stiffness in all directions after screw fixation was similar in both groups. The stiffness after one- and two-screw fixation was not restored to normal: the mean shear stiffness restored ratio was less than 50% and the mean torsional stiffness restored ratio was less than 6% in both groups. BMD did not correlate with mean stiffness after screw fixation in both groups.
One- and two-screw fixation for type II dens fractures provide similar stability but neither restores normal shear or torsional stiffness.
One-screw fixation might be used as an alternative to two-screw fixation. Assumed BMD should not influence surgical decision making.
前路螺钉固定已广泛应用于治疗Ⅱ型齿突骨折。然而，对于单螺钉固定与双螺钉固定哪种更合适，仍存在争议。
问题/目的：我们提出了三个问题：（1）单螺钉固定与双螺钉固定在抗剪刚度和扭转刚度方面是否存在差异？（2）螺钉固定后能否恢复至正常的抗剪刚度和扭转刚度？（3）螺钉固定后的刚度与骨密度（BMD）是否相关？
我们将 14 个新鲜颈椎轴向随机分为两组（每组 7 个）：一组接受单螺钉固定，另一组接受双螺钉固定。采用无损低载试验在六个方向上测量抗剪和扭转刚度。然后在齿突基部行横向截骨，并使用单螺钉或双螺钉固定。在相同的测试条件下再次测试抗剪和扭转刚度。
两组螺钉固定后的各方向平均刚度相似。单螺钉和双螺钉固定后的刚度均未恢复至正常：两组的平均抗剪刚度恢复比均小于 50%，平均扭转刚度恢复比均小于 6%。两组的 BMD 与螺钉固定后的平均刚度均无相关性。
对于Ⅱ型齿突骨折，单螺钉固定与双螺钉固定提供相似的稳定性，但均不能恢复正常的抗剪或扭转刚度。
单螺钉固定可作为双螺钉固定的替代方法。假设的 BMD 不应影响手术决策。
