不同内固定器固定股骨髁上骨折的生物力学比较

摘要

背景：治疗股骨髁上骨折的内固定方法很多，其中主要有偏心位固定的钢板类和中心位固定的髓内钉类。由于两者生物力学特性的差异，在治疗股骨髁上骨折的临床疗效也不同。n　　目的：对治疗股骨髁上骨折的两种固定器进行生物力学对比，探讨两种固定器固定股骨髁上骨折时的应力分布差异，从而为临床选择理想的内固定器提供理论依据。n　　方法：选择12套成人尸体股骨，将股骨髁上横行锯断，制作股骨髁上骨折模型。将骨折标本解剖复位后，按照手术操作方法用微创内固定系统和逆行交锁髓内钉固定。在骨折断面及钉道周围共粘贴6个电阻应变片，然后将骨折模型分别置于Zwick Z100电子万能材料实验机及扭转试验机(RNJ-500)上，以线性载荷0-400 N、扭转载荷0-20 N·m加载，分析局部应力，测量两种固定器在相同载荷条件下骨折断面及钉道周围应力的大小和分布特点。n　　结果与结论：在实验载荷条件下，逆行交锁髓内钉组和LISS钢板组骨折断端和钉道周围应力均随着轴向载荷和扭转载荷的增大而增大。在同一轴向载荷下，逆行交锁髓内钉组较LISS钢板组在6个测试应变点应变值大(P<0.01)；在同一扭转载荷下，LISS钢板组较逆行交锁髓内钉组在6个测试应变点应变值大(P<0.01)。结果显示，逆行交锁髓内钉固定股骨髁上骨折中可明显降低应力遮挡，从而利于应力传导，并具有良好的抗扭转能力，从生物力学角度可以推广使用。%BACKGROUND:There are various fixation methods in the treatment of supracondylar femoral fractures, including plates and interlocking intramedul ary nails. Due to differences in biomechanical properties, the clinical curative effect of the two methods in the treatment of supracondylar femoral fracture is different. n OBJECTIVE:To compare the biomechanical properties of two fixations in the treatment of supracondylar femoral fractures, explore the stress distribution differences of two fixations for supracondylar femoral fractures, and provide clinical basis for the selection of ideal fixation. n METHODS:Twelve sets of adult cadaveric femoral bone were selected, and the supracondylar femoral bone was sawn with an electric saw to establish supracondylar femoral fracture models. After anatomic reduction, the fracture samples were fixed with less invasive stabilization system (LISS) plates and retrograde interlocking intramedul ary nails, respectively. Six strain gages were mounted near the fracture plane and pin track, then the fracture models were placed in the Zwick Z100 electronic universal material test machine and torisional testing machine (RNJ-500), receiving a linear load of 0-400 N and a torisional load of 0-20 N·m. Local stresses were detected, and their distributions under the same load in the two fixations were also measured. n RESULTS AND CONCLUSION:In the experimental loading condition, the stress at the fracture end and around the pin track increased with the increase of the load both in the LISS plate groups and retrograde interlocking intramedul ary nail groups. In the same linear loading, the strain value at six testing points in the retrograde interlocking intramedul ary nail groups was higher than that in the LISS plate groups (P<0.01);in the same torsional loading, the LISS plate groups showed high strain value than the retrograde interlocking intramedul ary nail groups in the six test points (P<0.01). Retrograde interlocking intramedul ary nails can obviously reduce stress-shielding in the treatment of supracondylar femoral fractures, which is beneficial to the stress conduction. It also resists axial force and torsion. Therefore it can be applied in the clinical practice.