不同内固定器固定股骨颈骨折的生物力学比较研究

目的 对治疗股骨颈骨折的几种常用内固定器进行生物力学对比,为临床选择理想的内固定器提供理论依据.方法 利用聚甲基丙烯酸甲酯(poly methylmethacrylate,PMMA)制作人工股骨模型12个,按照人体股骨颈骨折时最常见的Pauwels 70.角用电锯锯断,造成内收型股骨颈骨折模型.将骨折标本解剖复位后,按手术操作方法用动力髋螺钉(dynamic hip screw,DHS)、3枚空心螺钉、股骨近端髓内钉(proximal femoral nail,PFN)和动态套筒式三翼钉不同置人物加以内固定.标本模拟人体单足站立位固定于Instron - 8874液压伺服力学实验测试机上,选择股骨近端15个点作为应变测试点,以10 mm/min加载速度、线性载荷0～1200 N分级加载,测定各组于1200N载荷下各点的应变值、不同载荷下头下沉位移和主压力侧8点的应变值.结果 1200N载荷下各组均在8点处出现峰值,DHS组、3枚空心螺钉组、PFN组和动态套筒式三翼钉组应变值分别为(-700±35)με、(-756±14)με、(-1362±136)με和(3024±127) με,两两比较差异均有统计学意义(P＜0.01).同一载荷下,动态套筒式三翼钉组股骨头下沉位移大于空心螺钉组和PFN组(P＜0.01),但小于DHS组(P＜0.01).同一载荷下,动态套筒式三翼钉组在主压力侧8点处的应变值均比其他三组的应变值大,其差异均有统计学意义(P＜0.01)；同一固定组,随着载荷的增大,应变值也逐渐增大.结论动态套筒式三翼钉固定股骨颈骨折稳定可靠,从生物力学角度可以推广使用.

Biomechanical study of different internal-fixations in femoral neck fractures

Objective To compare the biomechanical effect of several commonly used internal fixators in treating the femoral neck fractures so as to provide clinical basis for the selection of ideal internal fixation.Methods Twelve artificial PMMA femoral models were selected,and the central neck of the specimens was sawn with an electric saw at Pauwels angle of 70° to form adduction type femoral neck fracture models.After anatomic reduction,the specimens were fixed with dynamic hip screw ( DHS),three hollow screws,proximal femoral nail (PFN) and dynamic sleeve three-wing screw according to the operative approach,respectively.Instron-8874 servo-hydraulic mechanical testing machine was used to fix the specimens which simulated uniped standing.Fifteen key points on proximal femur were selected as test points and were given gradation loading at speed of 10 mm/min with linear load 0-1 200 N.The strain of each point under 1200 N load,head sink displacement under different loads and the strain of eight points on principal pressure side were measured.Results There was a peak at the eight resistance strain gage at 1200 N load and the strain values of the DHS,three hollow screws,PFN and dynamic sleeve three-wing screw were (700 ±35) μεz,(756 ± 14) με,( 1362 ± 136) με and (3024 ± 127) με,with statistical significance (P ＜ 0.01 ).Under the same load,the head sink displacement in the group of dynamic sleeve three-wing screw was greater than that of the hollow screws group and the PFN group ( P ＜0.01 ),but smaller thau that of the DHS group ( P ＜ 0.01 ).The strain values at the eight resistance strain gage in the group of dynamic sleeve three-wing screw was larger than that of the other three groups under the same load (P ＜ 0.01 ),and the strain values increased with the increase of load at the same fixation group.Conclusion Dynamic sleeve three-wing screw has good biomechanical stability for treatment of femoral neck fracture,which can be applied in the clinical practice.