不同内植物固定耻骨上下支骨折生物力学特征的比较

Comparison of biomechanical characteristics of superior and inferior pubic ramus fractures fixed with different internal fixation methods

背景:经皮逆向空心螺钉、微创经皮钢板广泛应用于单侧耻骨支骨折中,但存在误穿髋关节和损伤骨盆内侧滋养动脉等缺点。一种新型逆行耻骨上支髓内钉治疗骨盆前环骨折拥有透射次数少和手术时间短等优点,但目前缺乏上述3种内植物生物力学特征的验证。目的:通过有限元分析方法,比较在不同工况下经皮逆向空心螺钉、微创经皮钢板和逆行耻骨上支髓内钉治疗耻骨上下支骨折的生物力学差异。方法:收集1名志愿者的骨盆CT数据,将数据导入mimics 20、Geomagic Wrap 2021、Soildworks 2019中,建成3种内固定治疗单侧耻骨支骨折的几何模型,分别为空心螺钉组、钢板组、髓内钉组。分别将上述模型导入Ansys 2022软件设置垂直工况、开书样工况、剪切工况进行前处理和计算,比较分析内植物的力学稳定性。结果与结论:①在垂直工况下,空心螺钉治疗单侧耻骨骨折的生物力学稳定性较钢板和髓内钉更为优秀,其内植物应力峰值最小,其余两组对比空心螺钉组峰值增加4倍以上;②在开书样工况下,钢板治疗单侧耻骨骨折有更好的生物力学稳定性,钢板组降低耻骨上支断端应力有较好表现,其他两组的应力较钢板组增加5倍以上;③在剪切工况下,髓内钉治疗单侧耻骨骨折表现出良好的生物力学稳定性,其维持骨盆位移效果最佳,其他两组骨盆位移比髓内钉组增加了25%以上;④提示不同内植物在生物力学上存在差异性:逆行经皮空心螺钉在垂直工况下内植物应力峰值最小,微创经皮钢板在开书样工况下减小耻骨上支断端应力最优,逆行耻骨上支髓内钉在剪切工况下骨盆位移最小,可以将内植物生物力学差异性与患者临床实际情况相结合,选择最优内植物治疗方式。

BACKGROUND:Percutaneous retrograde screws and minimally invasive percutaneous plates are extensively used in the treatment of unilateral pubic ramus fractures.However,the above internal fixations have the disadvantages of mistakenly penetrating the hip joint and damaging the medial pelvic trophoblastic artery.A new type of retrograde superior pubic ramus intramedullary nail offers advantages,such as fewer radiographic exposures and shorter surgery times,but the validation of the biomechanical properties of the three endoprostheses is lacking.OBJECTIVE:To compare the biomechanical differences post-treatment of upper and lower pubic ramus fractures using percutaneous retrograde screws,minimally invasive percutaneous plates,and retrograde superior pubic ramus intramedullary nail under various conditions through finite element analysis.METHODS:Pelvic CT data were collected from one volunteer and imported into Mimics 20,Geomagic Wrap 2021,and SolidWorks 2019 to create geometric models of three types of internal fixation for treating unilateral pubic ramus fractures:hollow screw group,plate group,and intramedullary nail group.Each model was imported into Ansys 2022 software,where it was set up in vertical,book-opening,and shear conditions for preprocessing and calculation to compare and analyze the mechanical stability of the implants.RESULTS AND CONCLUSION:(1)In vertical conditions,the biomechanical stability of the hollow screw treatment for unilateral pubic fractures was superior to that of the steel plate and intramedullary nail,with the smallest peak stress in the implant,which was four times lower compared to the other two groups.(2)In book-opening conditions,the steel plate treatment for unilateral pubic fractures showed better biomechanical stability,particularly in reducing stress at the fracture ends of the upper pubic branch,with stress values five times higher in the other two groups.(3)In shear conditions,the intramedullary nail treatment for unilateral pubic fractures exhibited good biomechanical stability,maintaining the best pelvic displacement,with a 25%greater displacement observed in the other two groups.(4)These findings reveal the biomechanical differences of different implants:the peak stress of implants is the smallest under vertical working conditions with percutaneous retrograde screws.Minimally invasive percutaneous plates reduce the stress at the broken end of superior pubic branch under open-book working condition.Retrograde superior pubic ramus intramedullary nail of superior pubic branch maintains pelvic displacement under shear working condition.The surgeon can combine the biomechanical differences of the implants with the actual situation of pubic injury in clinical practice to make the best implant treatment.