Acutrak无头加压螺钉与AO空心拉力螺钉固定Hoffa骨折模型的生物力学研究

A Biomechanical Comparison of Acutrak Headless Compression Screw and AO Cannulated Lag Screw for the Fixation of Hoffa Fracture

目的比较Acutrak无头加压螺钉与AO空心拉力螺钉固定LetenneurⅠ型Hoffa骨折的强度和稳定性,为临床中Hoffa骨折固定方法的选择提供生物力学依据。方法选取12根新鲜冷冻成人尸体股骨标本制备LetenneurⅠ型Hoffa骨折模型。随机分为4组行不同方式内固定,A组:AO空心拉力螺钉由前向后进钉,B组:AO空心拉力螺钉由后向前进钉,C组:Acutrak无头加压螺钉由前向后进钉,D组:Acutrak无头加压螺钉由后向前进钉。检测骨折块间压力,然后依次进行轴向压缩、循环负荷、极限负荷测试,评估各组模型在不同应力下骨折块移位程度及极限负荷大小。结果骨折块间压力:A组(69.46±12.52)N,B组(65.51±15.00)N,C组(96.29±22.56)N,D组(97.76±22.36)N,组间差异无统计学意义(P>0.05)。轴向压缩测试骨折块间移位:A组(1.231±0.649)mm,B组(0.542±0.310)mm,C组(0.499±0.175)mm,D组(0.449±0.133)mm。A组与C组、A组与D组比较差异有统计学意义(P<0.05),其余各组间比较差异无统计学意义(P>0.05)。循环负荷测试:各组模型经受周期循环负荷后,骨折块轴向移位组间差异无统计学意义(P>0.05)。极限负荷测试:A组(1300.496±138.352)N,B组(1322.499±168.651)N,C组(2372.155±492.772)N,D组(2301.772±657.874)N,A组和C组、A组和D组、B组和C组、B组和D组差异有统计学意义(P<0.05),A组和B组、C组和D组差异无统计学意义(P>0.05)。结论 Acutrak无头加压螺钉固定LetenneurⅠ型Hoffa骨折的强度和早期稳定性优于AO空心拉力螺钉,更有利于骨折Ⅰ期愈合。螺钉进针方向对AO空心拉力螺钉固定效果有影响,但对Acutrak无头加压螺钉无影响。

Objective To compare the stability, strength of Letenneur type I Hoffa fractures fixed by Acutrak headless compression screws and AO cannulated lag screws. Methods 12 models of Letenneur type I Hoffa fractures were randomly divided into 4 groups, which were fixed with two AO cannulated lag screws or Acutrak headless compression screws anteroposteriorly or posteroanteriorly. The stress between two fragments of all specimens was tested. Axial compression test, the cycle load test and the limit load test were successively performed in every specimen. Results In axial compression test, displacement of Acutrak headless compression screw groups was lower than that of AO cannulated lag screw anteroposteriorly （P〈0.05）. The load to failure for Acutrak headless compression screw groups was higher than that of AO cannulated lag screws （P〈 0. 05）, no matter in anteroposterior or posteroanterior direction. Conclusion The strength and stability of Letenneur type I Hoffa fractures fixeded with Acutrak headless compression screw were superior to those provided by AO cannulated lag screw. The direction of screw affects the initial stability for AO cannulated lag screw, other than Acutrak headless compression screw.