膨胀式椎弓根螺钉的强度测试

Strength Evaluation of Expansion Pedicle Screw

测试膨胀式椎弓根螺钉(Expansive Pedicle Screw,EPS)的耐疲劳强度及抗折弯强度。在超高分子聚乙烯材料上对短尾型EPS螺钉、万向型EPS螺钉和Tenor螺钉进行100万次的周期载荷疲劳实验;用特殊夹具分别固定短尾型EPS螺钉、万向型EPS螺钉和Tenor螺钉,并于生物力学实验机上进行螺钉机械强度测试。在超高分子聚乙烯材料上对螺钉进行100万次的周期载荷疲劳实验完成后短尾型EPS螺钉、万向型EPS螺钉和Tenor螺钉均未发生疲劳现象,短尾型EPS螺钉的最大折弯力(6.52±0.39kN)与Tenor螺钉的最大折弯力(6.86±0.42kN)之间的差异无统计学意义(P>0.05),而万向型EPS螺钉的最大折弯力(5.69±0.39kN)与TENOR螺钉的最大折弯力(6.86±0.42kN)之间的差异有统计学意义(P<0.05)。短尾型EPS螺钉和万向型EPS螺钉的抗疲劳强度与非膨胀螺钉无明显差异,并未因其中空结构而使抗疲劳强度下降。虽然万向型EPS螺钉的机械强度较普通螺钉低,但是足够承受人体上半身的载荷。

To measure the fatigue resistance and anti-bending strength of expansion pedicle screw（EPS）.Fatigue testing was performed on ultra-high molecular weight polyethylene blocks served as vertebral elements in a corpectomy model.The short-tail EPS,multiaxial EPS screw and Tenor were fixed on Special fixture,and tested the Mechanical strength.No screws were broken or bent at the end of fatigue testing in groups of short-tail EPS,multiaxial EPS screw and Tenor.The difference between the largest anti-bending force of short-tail EPS（6.52±0.39）kN and Tenor screw（6.86±0.42）kN was not significant（P〉 0.05）,the difference between multiaxial EPS（5.69±0.39）kN and Tenor screw（6.86±0.42 kN）was significant（P〈0.05）.The fatigue characteristic of short-tail EPS and multiaxial EPS is similar to Tenor screws,Although the mechanical strength of multiaxial EPS was lower than Tenor screws,but enough to bear the load of human upper body.