加长骶髂螺钉和普通骶髂螺钉治疗单侧骶骨骨折的生物力学比较

Biomechanical comparison of lengthened and conventional sacroiliac screws in treatment of unilateral sacral fracture

目的 对加长和普通两类骶髂螺钉固定治疗单侧骶骨纵行骨折的生物力学特征进行比较,从而为临床置钉提供参考. 方法 采用三维有限元方法,建立Tile C型骨盆损伤（单侧骶骨纵行骨折）模型,分别模拟加长和普通两类骶髂螺钉（共6种固定方式）进行固定,对模拟站立位状态下骨盆后环的稳定性、螺钉最大应力等指标进行量化和比较. 结果 骶1和骶2各自1枚加长骶髂螺钉固定均优于同层面的1枚普通骶髂螺钉固定;两个骶骨层面各置1枚加长骶髂螺钉优于两个骶骨层面各置入1枚普通骶髂螺钉;双层面的加长骶髂螺钉固定组合优于单层面的加长骶髂螺钉;双层面2枚普通骶髂螺钉固定组合优于单层面1枚普通骶髂螺钉;无论加长骶髂螺钉还是普通骶髂螺钉,在骶2层面进行固定均优于骶1层面. 结论 针对Tile C型骨盆损伤的单侧骶骨纵行骨折,应尽量选择骶1、骶2加长骶髂螺钉固定,而且最好选择二者组合,即便由于条件所限无法使用加长骶髂螺钉固定,也尽可能选择双层面普通骶髂螺钉固定;若使用单层面单枚普通骶髂螺钉或加长骶髂螺钉固定治疗单侧骶骨纵行骨折,则最好选择骶2层面.

Objective To compare the mechanical characteristics of lengthened and conventional sacroiliac screws for fixation of unilateral vertical sacral fracture so as to provide evidences for clinic practice.Methods A three-dimensional finite element model of Tile type C pelvic injury （unilateral vertical fracture of the sacrum） was developed.Six different methods for internal fixation with lengthened and conventional sacroiliac screws were performed.Stability of posterior pelvic ring during stance phase and maximum stress on the screws after different fixation methods were measured and compared.Results Mobilization with one lengthened sacroiliac screw at S1 or S2 single-segment provided better biomechanical properties than with one conventional sacroiliac screw at the same segment.Better biomechanical properties were also observed in the bisegmental stabilization with each one lengthened sacroiliac screw compared to bisegmental stabilization with each one conventional sacroiliac screw; in the bisegmental lengthened sacroiliac screw fixation compared to single-segmental lengthened sacroiliac screw fixation; in the bisegmental stabilization with two conventional sacroiliac screws compared to single-segmental stabilization with one conventional sacroiliac screw.No matter which kind of sacroiliac screw was applied,S2 segment stabilization had better biomechanical properties over S1 segment stabilization.Conclusions For unilateral vertical sacral fracture due to Tile type C pelvic ring injury,S1 or S2 lengthened sacroiliac screws should be selected as possible,the best with combination of lengthened sacroiliac screw and conventional sacroiliac screw.Even if lengthened sacroiliac screws cannot be used due to limited conditions,bisegrnental fixation with conventional sacroiliac screws should be considered whenever possible.No matter which kind of sacroiliac screw is applied in single segment fixation,the fixation of S2 segment is the preferred choice.