全膝置换术后髁上骨折三种内固定有限元分析

Finite element analysis on three internal fixations for Kim type IB femoral supracondylar fracture subsequent to total knee arthroplasty

[目的]利用三维有限元分析的方法,比较全膝置换术后利用单锁定钢板、髓内钉、双锁定板三种方式固定Kim IB型股骨髁上骨折的生物力学特征。[方法]将志愿者股骨CT图片及股骨假体的扫描数据,三维重建后与在Cero3.0中设计的外侧锁定钢板、内外侧双锁定钢板、股骨远端髓内钉模型装配、划分单元、赋予材料属性,构成单钢板、髓内钉组、双钢板组三个有限元模型。加载单足站立、双足站立两种工况进行力学分析。[结果]三组模型中内固定承受应力依次为单钢板组>髓内钉组>双钢板组,三组之间差异有显著统计学意义(P<0.05)。假体外髁承受应力比较单钢板组显著高于髓内钉组和双钢板组(P<0.05)。相同载荷下骨折端位移单钢板组>髓内钉组>双钢板组,三组之间差异有显著统计学意义(P<0.05)。单钢板组与髓内钉组中单足站立载荷在骨折端产生的位移显著大于双足站立载荷(P<0.05)。[结论]双锁定钢板不仅有利于股骨髁上骨折骨折断端稳定,而且能够减小股骨假体内外侧髁应力差异,有利于假体的稳定。

[Objective] To compare biomechanical characteristics of single locking plate, intramedullary nail and double locking plates used for internal fixation of Kim type IB femoral supracondylar fracture of femur subsequent to total knee arthroplasty by using finite element analysis. [Methods] Based on a 3-dimension model of femur created by using CT image data of a volunteer, the finite element models of single locking plate, intramedullary nail and double locking plates used for internal fixation Kim type IB femoral supracondylar fracture subsequent to total knee arthroplasty were made individually by using corresponding software. Under loading, the stress nephogram was analyzed, while the Von Mises stresses of the interesting areas and displacements of the fractures under 2 000 N in standing on one foot or two feet were measured and compared among the 3 internal fixations groups. [Results] The Von Mises stress on the fracture ends ranked up-down in the sequence of single plate > intramedullary nail > double plates, which proved statistically significant(P<0.001), while the stress on the lateral condyle of the femoral component in the single plate was significantly greater than those in the intramedullary nail and the double plates(P<0.001). Under the same loading, the displacement of fracture ends arranged up-down in the sequence of single plate > intramedullary nail > double plates with a statistically significant difference(P<0.001), additionally, it proved significantly greater in standing on one foot than those in standing on two feet in the single plate and intramedullary nail(P<0.001). [Conclusion]The double locking plates are benefit not only to stabilize the fracture ends, but also reduce the stress difference between the lateral and medial condyles of femoral component, which facilitate the prosthetic survival.