摘要
目的 比较锥形与柱形椎弓根螺钉在下胸段及腰段的生物力学差异性及影响因素。方法 将6具成人新鲜T_9～L_5脊柱标本分解为 54个椎体标本。随机选取一侧按标准方法放置特制试验用直径5.5mm锥形螺钉,然后在MTS力学试验机上先后测量其最大扭矩及最大拔出力。在对侧以同样的方法进行5.5mm柱形螺钉的实验。结果在下胸段,锥形螺钉的最大扭矩(1.445 ±0.66)N·m显著性大于柱形的最大扭矩(1.073±10.42)N·m(P=0.021),而在腰段锥形(1.017±0.43)N·m和柱形(1.28±0.50)N·m螺钉的最大扭矩没有明显差异(P=0.416)。无论在下胸段还是腰段,锥形螺钉与柱形螺钉的最大拔出力均无显著性差异。从下胸段到腰段,螺钉的最大拔出力逐步增加。柱形椎弓根螺钉的最大扭矩与最大拔出力呈正相关(r=0.629)锥形螺钉的最大扭矩与最大轴向拔出力的相关性不显著(r=0.179)。结论 相同直径的锥形与柱形螺钉的最大拔出力相近,且锥形螺钉在其直径与椎弓根内径相近时具有较高的扭矩。螺钉的最大扭矩与最大拔出力的相关关系要视螺钉的类型而定。
Objective To compare the biomechanical performance of the conical and cylindrical pedicle screw in lower
thoracic and lumbar vertebra. Methods 54 vertebral specimens were obtained from 6 fresh normal frozen cadavers (T_9 -
L_5). The experimental 5.5 mm conical pedicle screw was implanted at one pedicle at random and tested with an MTS machine
(858 Bionix Ⅱ). The maximal insertion torque was firstly measured, then the maximal pull-out strength. The same experiment
was done with the cylindrical screw on the other side. Strength datas were recorded. Results In the lower thoracic region the
torque of conical screw(1.445±0. 66) N·m was distinctly higher than that of the cylindrical screw(1.073±0.42) N·m(P
=0.021), but in the lumbar region this difference did not exist (P = 0.416). Conical and cylindrical screws had similar
pull-out strength in these two regions. From lower thoracic to lumbar vertebra, the pull-out strength was escalated. The corre-
lation between insertion torque and pull-out strength was statistically significant with the cylindrical screw(r =0.629), but not
with the conical screw (r =0. 179). Conclusion The conical screw has the similar pull-out strength with the same diameter
cylindrical screw. And when the diameter of conical screw is similar to the inner-diameter of pedicle, it has a higher insertion
torque. The relation between the insertion torque and pull-out strength is based on the type of screw.
出处
《脊柱外科杂志》
2004年第4期220-223,共4页
Journal of Spinal Surgery
