髂骨垫片对髂骨螺钉疲劳载荷后下沉位移的影响

Effect of an iliac bone plate on the subsidence of iliac screw after fatigue loading

中文关键词:  脊柱-骨盆固定  髂骨螺钉  髂骨垫片  生物力学

英文关键词:Spino-pelvic reconstruction  Iliac screw  Iliac bone plate  Biomechanics

中文摘要:

  【摘要】 目的：评价自主设计的髂骨垫片对髂骨螺钉疲劳载荷后下沉位移的影响。方法：6具成人新鲜尸体腰椎-骨盆标本用于实验。经双能X线吸收法测定L1~L4平均骨密度后，随机将髂骨垫片放置在一侧髂骨进钉点处（A组），另一侧无垫片作为对照（B组）。将直径7.5mm、长度70mm的髂骨螺钉分别置入左右侧髂骨，在MTS材料实验机上，向螺钉尾部施加100~400N垂直循环载荷20000次，记录每5000次载荷后两侧髂骨螺钉的下沉位移并比较。结果：6具标本的腰椎骨密度为0.78~1.06g/cm2，平均0.89±0.06g/cm2。所有螺钉顺利承受20000次的垂直载荷。在第5000、10000、15000和20000次轴向压缩载荷点上，A组髂骨螺钉的下沉位移分别为0.28mm、0.36mm、0.48mm和0.66mm；B组髂骨螺钉的下沉位移分别为0.34mm、0.69mm、0.88mm和1.07mm。在第5000次载荷点上，A组和B组螺钉下沉位移的差异无显著性（P>0.05）；在第10000、15000和20000次载荷点上，A组与B组螺钉下沉位移的差异均有显著性（P<0.05）。20000次载荷后X线片发现A组无螺钉松动，B组5枚螺钉松动。结论：髂骨垫片可有效减少髂骨螺钉疲劳载荷后的下沉位移，防止髂骨螺钉松动。

英文摘要:

  【Abstract】 Objective：To evaluate the biomechanical effect of a self-designed iliac bone plate on the subsidence of iliac screw after fatigue loading.Method：Lumbo-pelvic specimens from 6 adult fresh cadavers were used in this study，their mean bone mineral densities（BMD） of L1-L4 were measured by using dual-energy radiograph absorptiometry.The iliac bone plate was randomly placed at the iliac screw entry point of one-side ilium（group A），while the other side without iliac bone plate served as the control（group B）.Then，the iliac screws with 70mm length and 7.5mm diameter were inserted into the ilium bilaterally.On a MTS testing machine，a dynamic compressive loading of 100-400N was added to the screw head for 20000 cycles.The screw subsidence displacements following each 5000 cyclic loadings were measured and compared between two groups.Result：The average BMD value of 6 specimens was 0.89±0.06g/cm2，ranged from 0.78g/cm2 to 1.06g/cm2.All the screws passed the 20000 cyclic loadings smoothly.At the time-points of the 5000th，10000th，15000th，and 20000th cyclic loadings，the subsidence displacements of iliac screw in group A were 0.28mm，0.36mm，0.48mm and 0.66mm respectively；while those in group B were 0.34mm，0.69mm，0.88mm and 1.07mm respectively.After the first 5000 cyclic loadings，no significance with respect to subsidence displacement was detected between two groups（P>0.05）.However，at the 10000th，15000th and 20000th cycles，significant difference was noted between two groups（P<0.05）.After the 20000 cyclic loadings，no screw in group A and 5 screws in group B were found loosen under radiograph.Conclusion：The iliac bone plate can effectively resist the subsidence of iliac screw following fatigue loading and protect iliac screw against loosening.