低弹性模量接骨板固定股骨干骨折的有限元分析

Low modulus titanium alloy plating for femoral shaft fractures： A finite element analysis

目的 探讨不同弹性模量接骨板内固定对股骨干骨折应力及其分布的影响. 方法采用64排螺旋CT对一名健康成年男性股骨进行层厚为0.5 mm的扫描,获得股骨CT数据,再通过软件三维反求得到股骨有限元模型.模拟股骨中段骨折模型,分别采用Ti-6Al-4V（高弹性模量组,弹性模量为110 GPa）和Ti2448（低弹性模量组,弹性模量为30 GPa）两种材料的8孔接骨板进行固定.分析两种不同弹性模量接骨板内固定在轴向压缩、四点前后弯曲和扭转载荷下股骨的应力分布情况,并以应力云图的方式直观地显示应力分布规律. 结果在3种载荷下,两组均在断端接触部位出现最大应力.在轴向压缩载荷下,低弹性模量组最大应力值为30.00 MPa,大于高弹性模量组（21.68 MPa） 螺孔内最大应力值（11.47 MPa）小于高弹性模量组（13.89 MPa）,应力云图显示：高弹性模量组骨组织呈多个应力梯度分布,而低弹性模量组骨组织应力分布较均匀.在四点前后弯曲载荷下,低弹性模量组最大应力值为11.23 MPa,大于高弹性模量组（7.96 MPa）.在扭转载荷下,两组股骨应力分布均较均匀,低弹性模量组最大应力值（63.82 MPa）大于高弹性模量组（43.97 MPa）,螺孔内最大应力值（11.47MPa）小于高弹性模量组（31.24 MPa）. 结论低弹性模量接骨板内固定股骨干骨折,其骨折断端应力刺激增大,螺孔内应力集中减轻,接骨板的应力遮挡效应减小.

Objective To investigate the effects of internal plating with high and low moduli of elasticity on the stress and its distribution on the femoral shaft fracture. Methods A femur from a normal Chinese adult male was scanned by 64-detector row helical CT at 0. 5 mm interval. The CT images were used to establish a finite element model of the femur by software. The mid-femoral fracture was simulated in the model and fixated by eight-hole plates of Ti-6Al-4V （high modulus group, E = 110 GPa） and of Ti2448 （low modulus group, E = 30 GPa）. When the femur was in axial compression, flexion and torsion loads, the stress and its distribution on the bone fracture site were analyzed to compare the biomechanics of the plates with high and low moduli. Results Under axial compression load, the contact stress between fracture ends in the low modulus group was larger than that in the high modulus group, while the max stress at the hole （11.47MPa） was smaller than that in the high modulus group （13.89 MPa） . Under four-point bending load, the contact stress in the low modulus group was still larger, while the bending movement was smaller. Under the torsion load, stress on the femur was well-distributed in both groups, but the max stress at the hole in the low modulus group （11.47 MPa） was smaller than that in the high modulus group （31.24 MPa）. Conclusions Under internal fixation by plates of low modulus, the stress stimulus at the fracture site may be increased,while the stress concentrated at the hole may be decreased. The stress shielding of the low modulus plate may also be modified.