不同数量和空间构型的空心拉力螺钉治疗股骨颈骨折的有限元分析

Three-dimensional finite element analysis of different quantity and configuration of cannulated lag screws for femoral neck fractures

目的探讨4种不同数量和空间构型的空心拉力螺钉治疗股骨颈骨折的生物力学差异。方法利用1名65岁健康男性志愿者右股骨颈近端DICOM格式的CT图像，通过三维虚拟软件建立PauwelsI、Ⅱ、Ⅲ型股骨颈骨折模型和4种不同数量及构型的内固定模型（3钉正三角形、3钉倒三角形、4钉矩形、4钉菱形）。将模型导入有限元分析软件Ansys软件中，模拟直立情况下内固定及骨折区域的位移及应力分布情况。观测内固定物应力峰值、头侧骨折断端应力峰值和股骨头处位移峰值。结果对于4种不同数量及正三角形、倒三角形、矩形、菱形构型的内固定模型，在Pauwels Ⅰ型骨折时，应力峰值分别为46．382，32．159，43．985，24．342MPa；头侧股骨颈骨折断端应力峰值分别为5．840，7．440，3．731，6．311MPa；股骨头处位移峰值分别为0．610，0．608，0．598，0．595mm。在Pauwels1 Ⅰ型骨折时，应力峰值分别为46．763，39．979，49．619，25．692MPa；头侧股骨颈骨折断端应力峰值分别为4．971，7．332，3．161，5．734MPa；股骨头处位移峰值分别为0．634，0．635，0．622，0．631mm。在Pauwels Ⅲ型骨折时，应力峰值分别为51．432，39．477，51．515，26．949MPa；头侧股骨颈骨折断端应力峰值分别为6．163，10．070，5．257，9．552MPa；股骨头处位移峰值分别为0．662，0．654，0．644，0．644mm。结论4枚菱形排列的空心拉力螺钉固定股骨颈骨折具有更优的应力分散作用，能够使骨折断端更加稳定且能提供有效的滑动加压作用和抗扭力作用，具有更佳的生物力学优势，从而指导临床应用。

Objective To analyze biomechanical differences among quantity configurations of four common eannulated screws using three-dimensional finite element analysis. Methods The Dicom CT images of the right proximal femoral neck of a 65-year-old Chinese healthy volunteer were used to establish models of three kinds of different Pauwels types of femoral neck and four kinds of different quantity and configuration models （triangle, inverted triangle, rectangle, diamond） through three- dimensional virtual softwares. Models were imported into the finite element analysis software Ansys. After axial load application, the stress and displacement on the screws and femoral head were compared. The peak stresses on the screws, peak stresses on the femoral head break side and displacement peaks were observed. Results Four kinds of quantity and configuration models （triangle, inverted triangle, rectangle, rhombus） had different peak stress on the screws and femoral head break side and different displacement peak. Among Pauwels type I fractures, the peak stresses on the screws were 46. 382, 32. 159, 43. 985, and 24. 342 MPa; the peak stresses on the femoral head break side were 5. 840, 7.440, 3.731, and 6.311 MPa; the displacement peaks were 0. 610, 0. 608, 0. 598, and 0. 595 mm. Among Pauwels type Ⅱ fractures, the peak stresses on the screws were 46. 763, 39. 979, 49. 619, and 25. 692 MPa; the peak stresses on the femoral head break side were 4. 971, 7.332, 3. 161, and 5. 734 MPa; the displaeement peaks were 0. 634, 0. 635, 0. 622, and 0. 631 ram. Among Pauwels type m fractures, the peak stresses on the screws were 51. 432, 39. 477, 51. 515, and 26. 949 MPa, and the peak stresses on the femoral head break side were 6. 163, 10. 070, 5. 257, and 9. 552 Mpa; the displacement peaks were 0. 662, 0. 654, 0. 644, and 0. 644 ram. Conclusion The fixation of femoral neck fractures with four screws in a diamond position can guide clinical application, for the procedure has better stress dispersion effects, ensure fracture stablility, provide effective sliding compression and anti-torsion and have biomechanical advantages.