部分可吸收椎间融合器的设计及有限元分析

Design and finite - element evaluation of a partially bioabsorbable interbody fusion cage

目的设计部分可吸收椎间融合器(partially bioabsorbable interbody fusion cage,PBIFC),并应用有限元模型评估其生物力学性能。方法采用纳米羟基磷灰石/聚酰胺66(n-HA/PA66)和多聚氨基酸复合硫酸钙材料,设计并制作PB-IFC。建立完整L3/4腰椎节段的有限元模型并验证;在该模型上,模拟经前路植入PBIFC或同外形非吸收型椎间融合器n-HA/PA66 cage,分别建立植入即刻和植入4周的有限元模型;在L3上表面施加400 N轴向压缩预载荷和10 Nm扭矩,模拟脊柱压缩、前屈、后伸、旋转和侧屈5种运动,计算各模型的应力值及应力轮廓。结果植入即刻,PBIFC模型植骨的应力高于n-HA/PA66 cage模型;融合器及终板应力低于n-HA/PA66 cage模型;两个模型终板应力轮廓未见明显区别。植入4周时,PBIFC模型植骨的应力高于n-HA/PA66 cage模型;融合器及终板应力低于n-HA/PA66 cage模型,且差值较植入即刻时更大;PBIFC模型的终板应力轮廓较n-HA/PA66 cage模型大。结论 PBIFC较相同外形的非吸收型融合器具有更多的优点,是一种适宜的新型椎间融合器。

Objective To design a partially bioabsorbable interbody fusion cage（PBIFC） and to analyze its biomechanics using finite-element evaluation method.Methods A new type of PBIFC was designed and made from nano-hydroxyapatite/polyamide 66（n-HA/PA66） and multi-（amino acid） copolymer-calcium sulfate;a 3D finite-element model of L 3-L 4 segment was constructed and validated.A PBIFC or a non-absorbable cage of identical shape（n-HA/PA66 cage） was implanted via anterior approach on the model,and four models were established,including the immediate implantation model and 4-week implantation model of each cage.An axial compressive preload of 400 N and a torque of 10 Nm were applied to the L 3 segment to simulate spinal compression,flexion,extension,rotation,and lateral bending.The stress and stress contour of different loading conditions were calculated.Results Immediately after implantation,stresses of the bone graft in PBIFC model were higher than those in n-HA/PA66 cage model,while stresses of the cage and endplate in PBIFC model were lower;and no significant difference in stress contours on endplate was found between the two models.Four weeks after implantation,stresses of the bone graft in PBIFC were higher than those in n-HA/PA66 cage,and stresses of the cage and endplate in PBIFC model were lower,with the stress differences being greater than those of immediately after implantation.The stress contours on endplate in PBIFC model was larger than that in the n-HA/PA66 cage model.Conclusion PBIFC is probably more suitable than a non-absorbable cage of identical shape for lumbar interbody fusion.