摘要目的 比较亚洲型股骨近端防旋髓内钉、动力髁螺钉、动力髋螺钉固定股骨反转子间骨折后的生物力学性能.方法 测量正常股骨的生物力学性能后,制作18具成人股骨反转子间骨折模型,分别以亚洲型股骨近端防旋髓内钉(PFNAⅡ)、动力髁螺钉(DCS)、动力髋螺钉(DHS)随机进行固定.利用电阻应变片和位移传感器测量实验数据,制作不同内置物固定后,垂直应力作用下股骨近端位移-压力以及压力-骨折近段角度位移统计表,同时在扭转应力作用下制作扭转角-扭矩统计表.测量3组标本的垂直及扭转刚度并进行统计学比较,对3种不同内固定物在反转子间骨折治疗中的生物力学性能进行比较.结果 垂直载荷作用下,股骨近端下沉位移＜1.0 mm时(垂直应力小于500 N),PFNAⅡ、DCS两组之间的轴向应力值差异无统计学意义(P＞0.05).超过生理负荷后两实验组间差异有统计学意义(P＜0.05),且PFNAⅡ抗垂直压缩能力强于DCS,但PFNAⅡ应力遮挡较DCS更为明显;DHS抗垂直压力与PFNAⅡ差异有统计学意义.扭转应力作用下,在扭转角度≤4°时,3实验组间差异无统计学意义,当扭转角度加大后,PFNAⅡ抗扭转能力更强.3组不同内置物的刚度比较中,PFNAⅡ的垂直及扭转刚度最强,而DCS与DHS的扭转刚度差异无统计学意义(P＞0.05).结论 PFNAⅡ抗垂直及扭转应力的作用强于DCS和DHS.在生理载荷下,PFNAⅡ及DCS均可用于股骨反转子间骨折的治疗,但PFNAⅡ应力遮挡率较高.DHS固定组易导致固定失败,不应用来治疗股骨反转子间骨折.

abstractsObjective To compare the biomechanical performance of Asian proximal femoral nail anti-rotation (PFNA Ⅱ),dynamic condylar screw (DCS) and dynamic hip screw (DHS) for fixation of reverse oblique intertrochanteric fracture (ROIF).Methods Following measurement of the normal femur biomechanical properties,18 models mimicking ROIF in adults were established,which were randomly assigned to fixation with PFNA Ⅱ,DHS and DCS,respectively.Following measurement of the parameters by using resistance strain gages and displacement transducers,the proximal displacement-pressure and the pressure-proximal fracture segment angle displacement statistics tables were depicted under vertical stress,and the torsion angle-torque statistics tables were established by using different implants under torsional stress.The vertical and torsional stiffness were assessed for comparison on the biomechanical properties of different internal fixations in ROIF.Results Under vertical loadings,the difference in axial stress between PFNA Ⅱ and DCS was not statistically significant for a sinking displacement of the proximal femur of 1.0 mm or less,corresponding to the vertical stress of 500 N or less.A loading exceeding the physiologic limit resulted in a significant difference between two groups.Compared with DCS,the PFNA Ⅱ was associated with a heightened resistance to vertical compression and stress shielding (both P＜0.05).There was no significant difference between PFNA Ⅱ and DCS in the resistance to vertical loading.The difference among DHS,PFNA Ⅱ and DCS in the presence of a torsion angle of 4° or less was unremarkable under torsional stress.An increased angle of torsion was related to heightened anti-reverse capacity of PFNA Ⅱ.Comparison on the stiffness of three different implants evidenced that PFNA Ⅱ yielded the most significant vertical and torsional stiffness and that the difference between DCS and DHS was unremarkable.Conclusions The antiresistance capability to vertical and torsional stress of PFNA Ⅱ is stronger compared with DCS and DHS.The PFNA Ⅱ and DCS can be applied for the treatment of ROIF under physiological loadings,however,the PFNA Ⅱ is characterized by a higher stress shielding rate.Fixation failure is readily elicited by DHS,which is therefore not recommended for the treatment of ROIF.