新型动力化前路方形区钛板螺钉系统在不同置钉方法下固定髋臼骨折的有限元比较

Finite element comparison of different fixation methods of the new-type dynamic anterior plate-screw system for quadrilateral plate in the treatment of acetabular both-column fractures

目的采用三维有限元分析法研究新型动力化前路方形区钛板螺钉系统(DAPSQ)固定髋臼高位双柱骨折的生物力学特点,并比较其在不同方形区螺钉置钉方法下的生物力学稳定性。方法应用1例成年男性志愿者骨盆CT图像构建左侧髋臼高位双柱骨折的全骨盆有限元模型,并采用新型动力化前路方形区钛板螺钉系统固定。分别构建DAPSQ联合单方形区螺钉(A组)、双方形区螺钉(B组)、三方形区螺钉(C组)和四方形区螺钉(D组)固定模型,施加600 N垂直载荷或8N/m扭矩,模拟骨盆站位、坐位、站位+健侧旋转和站位+患侧旋转,比较各组内固定方法下骨折线平均位移和内固定应力分布情况。结果在站位、坐位、健侧旋转和患侧旋转4种工况下,方形区骨折线路径上各节点平均位移表现为A组>B组>C组>D组,组间比较显示D组位移显著低于A组和B组(P<0.05),C组和D组比较差异无统计学意义(P>0.05)。应力分析结果显示,站位和坐位下D组应力主要集中在钛板螺钉结合处,以近端第1枚方形区螺钉承担应力最大。结论新型动力化前路方形区钛板螺钉系统固定髋臼高位双柱骨折的生物力学性能可靠,推荐在方形区应至少置入3或4枚螺钉进行固定,且靠近坐骨大切迹的方形区螺钉为关键钉。

Objective To observe the biomechanical properties of a new-type dynamic anterior plate-screw system for quadrilateral plate(DAPSQ)for the treatment of double column acetabular fractures,and compare the biomechanical stability under different methods of quadrilateral screws placement.Methods A finite element model of left double column fracture was constructed with CT images of an adult male volunteer,and fixed with DAPSQ.The quadrilateral plate was fixed with four kinds of methods including single screw(A),double screws(B),three screws(C)and four screws(D).Axial load of 600 N and/or 8 N/m torque were applied to simulate the positions of standing,sitting and rotation.The average displacement of fracture line and the stress distribution of internal fixation were compared.Results The average displacement of the fracture line was A>B>C>D under the four positions(standing,sitting,unaffected side rotation,affected side rotation)and the displacement of group D was significantly lower than those of group A and group B.But there was no significant difference between group C and group D.The results showed that the stress of D model in sitting and standing position was mainly concentrated in the joint of titanium plate and screw,and the stress of the first quadrilateral screw near the large ischial notch was the largest.Conclusion The new-type DAPSQ shows reliable biomechanical stability in the fixation of double column acetabular fractures.This study recommends that 3 or 4 screws should be placed in the quadrilateral plate and the screw close to the large ischial notch is the key screw.