经椎弓根内固定的形态与生物力学研究

The Study of Morphology and Biomechanism of Pedicle Screw Fixation

目的 :提高临床医师对经椎弓根内固定技术的理论认识。方法 :应用直径 4.5mm ,5 .5mm ,6 .2 5mm和 7.0mm 4种不同直径的椎弓根螺钉于 16具T6～S1节段的新鲜尸体脊柱标本上观察 :(1)穿钉失败率 ;(2 )椎弓根膨胀变形率 ;(3)椎弓根螺钉把持力 ;(4)椎弓根椎体损伤分类。结果 :穿钉失败率与操作技术和椎弓根横径相关 ,在下胸椎失败率高主要与椎弓根横径密切相关 ,没有发生穿钉失败的椎弓根膨胀率 2 8.6 %～ 10 0 %。在下腰椎和骶1节段 ,穿钉失败率很低 ,没有观察到明显的膨胀。同一直径的螺钉从T6～L5把持力呈增加趋势 ,但在S1节段呈下降趋势。同一节段椎弓根 ,随螺钉直径增大其把持力亦增大。螺钉拔出时损伤多发生在T6～L1节段 ,以椎弓根椎体体交界区断裂常见。结论 :T10 以上应慎用经椎弓根内固定 ,在T10 ～L2 节使用直径 5 .5mm的椎弓根螺钉安全 ,而在L4 ～S1节段 7.

Objective: For better understanding of pedicle transpedicular fixation in clinical practice.Methods:4.5mm, 5.5 mm,6.25mm,7.0mm screws were inserted into T 6～S 1segments in 16 fresh specimens.(1)Failure of screw insertion,(2)pedicle expansion,(3)maximum pullout force and,(4)damage of pedicle and vertebral body were observed.Results:Failure of screw transpedicular insertion was related to surgeon's skill and pedicle width.Although 4.5mm screw was used,there was a high screw insertion failure rate at T 6～12 because of pedicle anatomy.Pedicle expansion rate was 28.6～100% at T 6～12 in those pedicles without failure after screw insertion.Screw insertion failure rate was lower at L 4～S 1 and no expansion was observed.Pullout strength was increasing from T 6 to L 5,but was decreasing at S 1.In the same pedicle,the bigger a screw's diameter was,the higher the pullout strength got.When screw was pulled out,Pedicle fractures were commonly happened at T 6～L 1 segments.Conclusion:The success of transpedicular fixation based on better understanding of pedicle anatomy and reasonable selection of pedicle screw diameter.