TiNi形状记忆锯齿臂环抱接骨板的生物力学测试及其对骨折愈合影响的研究

BIOMECHANICAL EVALUATION OF TiNi SHAPE-MEMORY SAWTOOTH-ARM EMBRACING PLATE AND ITS EFFECT ON FRACTURE HEALING

目的对TiNi形状记忆锯齿臂环抱接骨板(环抱器)、有限接触动力加压接骨板与静力型交锁髓内钉之间的生物力学进行比较研究,了解环抱器的生物力学特性,为临床应用提供理论依据。方法采用甲醛固定的成人尸体股骨成对标本8对,制备中段横形骨折模型后,随机一侧用环抱器固定为A组,对侧用有限接触动力加压接骨板固定为B组,A组测试后去除内固定再用静力型交锁髓内钉固定为C组,行轴向压缩、三点弯曲和扭转实验,比较力学性能并计算应力遮挡率。结果轴向压缩实验:各级轴向载荷下,A组应变值均大于B、C组(P<0.05);轴向载荷为100N时,各组位移值比较差异无统计学意义(P>0.05);200～600N时,A组位移值均大于B、C组(P<0.05)。三点弯曲实验:各级弯矩下,无论从板侧加载至对侧还是从对侧加载至板侧,A组桡度均大于B组及C组,比较差异有统计学意义(P<0.05),A组在相同载荷下从两侧加压所产生桡度差异无统计学意义(P>0.05)。扭转实验:各级扭矩下,A组扭角大于B组(P<0.05),但与C组比较差异无统计学意义(P>0.05)。600N载荷下,A、B、C组应力遮挡率分别为48.30%±22.99%、89.21%±8.97%、95.00%±3.15%,A组明显小于B、C组(P<0.01)。结论环抱器抗弯性能较有限接触动力加压接骨板和静力型交锁髓内钉弱,抗扭转性能较有限接触动力加压接骨板弱,但为中心型固定,且低应力遮挡率和轴向载荷产生的位移更有利于促进骨折端应力刺激。

Objective To investigate the detailed biomechanics of TiNi shape-memory sawtooth-arm embracing plate（TiNi SMA）by comparing with limited-contact dynamic compression plate（LC-DCP）and static interlocking intramedullary nail（SIiN）,so as to provide theoretical evidence for clinical application.Methods Eight paired cadaveric femurs immersed in formaldehyde were harvested from eight specimens of adults.After making X-ray films and modeling midpiece transverse fracture,one side randomly was fixed by TiNi SMA（group A）and SIiN（group C）orderly,the other side was fixed by LC-DCP（group B）.The axial compression,three-point bending（pressed from plate side and opposite side both of group A and group B,from inside of group C）,and torsion were tested,and the stress shielding rate was compared.Results At every classified axial compression load,the strains of group A were greater than those of group B and group C（P0.05）,the displacements of group A were greater than those of group B and group C（P0.05）except 100 N.At every classified three-point bending moment,the displacement of group A were greater than those of group B and group C pressed both from two sides,but there was no difference when pressing from two sides under the same load of group A（P0.05）.At every torsion moment,the torsion angels of group A were greater than those of group B（P0.05）,but equal to those of group C（P0.05）.At 600 N of axial compression load,the stress shielding rates of groups A,B,C were 48.30%±22.99%,89.21%±8.97%,95.00%±3.15%,respectively,group A was significantly less than group B and group C（P0.01）.Conclusion The anti-bending ability of TiNi SMA is weaker than LC-DCP and SIiN;the anti-torsion ability of TiNi SMA is weaker than SIiN,but TiNi SMA is a centertype internal fixation,the superior stress shielding rate and micromovement promote the stress stimulation of fracture,which makes it an ideal internal fixation device.