应用2种内固定方法对骨盆后环应力传导的生物力学比较

摘要

目的：比较应用微创可调式接骨板联合单枚骶髂螺钉与2枚骶髂螺钉固定骨盆后环对骨盆应力分布的影响。方法选取5具防腐成年男性骨盆标本，保留 L4至双侧股骨近端1／3，剔除软组织，保留完整的耻骨联合、双侧骶髂关节及周围韧带、双侧髋关节、双侧骶结节韧带、双侧骶棘韧带，黏贴应变片。将标本置于 BOSE 生物力学试验机，模拟双足站立中立位，垂直加载负荷至520 N，记录完整骨盆的应变值。制作 Tile C 型骨盆骨折模型，耻骨联合用钢板固定，后环骨折复位后依次应用2种方法进行固定。分别记录2种内固定方法固定骨盆后环时的应变值。结果完整骨盆在垂直负荷下，同一标本两侧对应位点的应变值差异无统计学意义（P ＞0．05），应变集中位点沿骶股弓走行分布。与完整骨盆的应变值相比，2种方法固定的骨盆后环，除位点5、6、10、11外，其余位点差异无统计学意义（P ＞0．05）。在500 N垂直负荷下，应用微创可调式接骨板联合单枚骶髂螺钉固定的骨盆各位点应变值更接近完整骨盆的应变值。结论完整骨盆在垂直负荷下的传导与骶股弓走行大致相同。应用微创可调式接骨板联合单枚骶髂螺钉固定骨盆后环比单纯使用2枚骶髂螺钉能更好地恢复力学的传导。%Objective To compare the stress distribution of posterior pelvic ring fixed with minimally invasive adjustable plate(MIAP)combined with one iliosacral(IS)screw and two IS screws.Methods Five embalmed specimens of adult pelvis were used.The soft tissue was removed from the specimens,and the spines from the fourth lumbar vertebra to the proximal one-third of both femurs were retained.The pubic symphysis,bilateral sacroiliac joints and ligments, bilateral hip joints,bilateral sacrotuberous ligaments and sacrospinous ligaments were intact.The strain gages were adhered to 32 sites distributed symmetrically.The specimens were placed in the biomecanical machine at a standing neutral posture.Vertical load up to 520 N was applied and the strain value of intact pelvic ring was recorded.The Tile C pelvic fractures were made.The symphysis pubis was fixed with plate,and the fracture of posterior pelvic ring was fixed with two kinds of internal fixators.The strain changes were recorded respectively.Results The symmetrical sites of the intact pelvic ring had similar strain changes(P >0.05).And the strain concentration sites ran along the sacrofemoral arch.Compared with the strain value of the intact pelvis,the strain changes of these sites(except site 5,6,10,11)in the pelvic fractures fixed with two kinds of internal fixation were not statistically significant(P > 0.05).Each strain value in the posterior pelvic ring fixed with MIAP combined with one IS screw was close to that in intact pelvis under 500 N vertical load.Conclusion In the intact pelvic ring,the conduction of vertical load runs along the sacrofemoral arch.The posterior pelvic ring fixed with MIAP combined with one IS screw can achieve better restoration of mechanical conduction than that fixed with two IS screws.