不同内固定方法治疗不稳定型粗隆间骨折的有限元分析

Finite element analysis on different internal fixation methods for treating unstable intertrochanteric fractures

目的利用三维有限元技术对不稳定型粗隆间骨折及动力髋螺钉(DHS)、股骨近端髓内钉(PFN)、股骨近端锁定钢板(PF-LCP)进行建模,分析3种方式固定不稳定型粗隆间骨折(AO分型31-A2型、31-A3型)的生物力学特性及其稳定性,以期对不稳定型股骨粗隆间骨折的治疗提供科学、客观、可靠的力学理论依据,指导临床治疗。方法建立31-A2型、31-A3型骨折模型(AO分型理想模型),分别采用DHS、PFN、PF-LCP 3种方式固定2种骨折,利用有限元方法模拟及分析正常载荷静止状态下单足中立位时3种方式固定2种骨折的生物力学稳定性。结果力学加载后在31-A2型、31-A3型骨折断面节点应力值及骨折线位移值最大者均为DHS,其次为PF-LCP,PFN应力及位移最小,三者最大应力在31-A2型分别为15.3、4.30、3.80 MPa,在31-A3型分别为56.9、31.16、16.63 MPa;3种方式骨折断面节点应力值比较,差异均有统计学意义(P<0.05)。三者最大位移值在31-A2型分别为381、334、269μm,在31-A3型分别为430、333、271μm。2种骨折断面应力最均匀的固定方式为PFN,其次分别为PF-LCP、DHS;骨折位移最小的固定方式为PFN,其次分别为PF-LCP、DHS。结论在31-A2型、31-A3型骨折中PFN固定效果最优,其次分别为PF-LCP、DHS;DHS对股骨近端具有明显的应力遮挡效应,且在31-A3型骨折断面外侧区有应力过分集中现象,容易导致固定衰败,是不适用的。

Objective To establish the models of unstable intertrochanteric fractures, dynamic hip screw（DHS）,proximal femoral nail（PFN） and proximal femoral-locking plate（PF-LCP） by applying the three-dimensional finite element technique and to analyze the biomechanical characteristics and stability of unstable intertrochanteric fractures（AO classification,type 31-A2 and type 31-A3） fixed with three kinds of methods in order to provide scientific,objective and reliable mechanical theoretical bases for treating unstable femoral intertrochanteric fractures and guiding clinical treatment. Methods The type 31-A2 and 31-A3 fracture models（ideal models of AO classification） were established and the 3 kinds of mode DHS,PFN and PF-LCP were adopted to fix the two kinds of fractures respectively. The biomechanical stability of two kinds of fractures fixed with three fixation approaches in the neutral position of a single foot under normal quiescent loads. Results In type 31-A2 and 31-A3 after mechanical loading,the DHS fixation had the greatest stress values of fracture surface and fracture line displacement,followed by PFLCP,and which of PFN fixation was minimal. The greatest stress values were 15.3,4.30,3.80 MPa for type 31-A2,56.9,31.16,16.63 MPa for type 31-A3,the differences among the three kinds of mode were statistically significant（P0.05）;the greatest displacement values were 381,334,269 μm for type 31-A2 type and 430,333,271 μm for type 31-A3 respectively. The most homogeneous stress of fixation mode in fracture cross section of two kinds of fracture was PFN,followed by PF-LCP and DHS;the minimal displacement of fixation mode was PFN,followed by PF-LCP and DHS. Conclusion The PFN fixation has best effect in type31-A2 and 31-A3 fracture,followed by PF-LCP and DHS;DHS has an obvious stress-shielding effect on proximal femur,moreover the over-centralized phenomenon of stresses appears in the lateral region of type 31-A3 fracture surface,which is easy to result in the fixation failure and is unsuitable.