带锁髓内钉中棒槌形高螺纹锁钉与通用锁钉抗弯强度及应力分布的比较

Bending strength and stress distribution of the interlocking intramedullary nails with high-thread wooden club-shaped nails versus traditional nails

背景:目前带锁髓内钉成为治疗四肢骨折的主要方法之一,但是常见的带锁髓内钉多为静力型带锁髓内钉,会出现断钉、退钉等现象,这些都跟带锁髓内钉中的锁钉强度有关,因而课题组设计了一种新型棒槌形高螺纹锁钉,并研究其力学特性。目的:测量棒槌形高螺纹锁钉的抗弯曲强度,分析其应力分布状况,对其生物力学性能进行测评,为其临床应用提供理论依据。方法:通过三点弯曲力学实验测量棒槌形高螺纹锁钉与通用锁钉的抗弯曲强度,运用有限元法模拟胫骨中段横行骨折,分析2种不同锁钉在胫骨骨折中的受力及应力分布情况。结果与结论:(1)三点弯曲实验中,棒槌形高螺纹锁钉在跨距20 mm和30 mm时的平均最大载荷分别为3.52 k N和1.81 k N,均比通用锁钉承受的载荷大;(2)有限元分析中,棒槌形高螺纹锁钉的平均最大位移与平均最大应力值均比通用锁钉小,且应力相对较分散;(3)使用棒槌形高螺纹锁钉的带锁髓内钉模型的平均最大应力值和最大轴向位移分别为131 MPa和3.27 mm,而使用通用锁钉的带锁髓内钉模型分别为162 MPa和4.07 mm;棒槌形高螺纹锁钉的平均最大应力值和最大轴向位移分别为26.5 MPa和0.323 mm,通用锁钉分别为34.3 MPa和0.407 mm;(4)结果表明,棒槌形高螺纹锁钉的抗弯曲强度较高,能够使应力相对分散,提高其抗疲劳强度,锁钉不易发生疲劳断裂。

BACKGROUND： Interlocking intramedullary nailing is a main method for bone fractures, but traditional static intramedullary nails usually lead to nail breakage and loosening. Thereafter, we design a novel high-thread wooden club-shaped screw （HTWCSS） and explore its mechanical properties. OBJECTIVE： To measure the bend strengths of HTWCSS, analyze its stress distribution, and to evaluate its biomechanical properties, thereby providing theoretical basis for its clinical application. METHODS： The bend strength of HTWCSS and traditional nails were measured via three-point bending experiments. Transverse fractures of the middle tibia were simulated using finite element method, and then the force and stress distribution of the two different nails were analyzed. RESULTS AND CONCLUSION： （1） The average maximum load of HTWCSS was 3.52 kN and 1.81 kN at span of 20 mm and 30 mm, respectively, which were larger than those of the traditional nails. （2） The average maximum displacement and the stress of HTWCSS were smaller than those of the traditional screws in finite element analysis, and the stress distribution was relatively dispersed. （3） The average maximum axial displacement and stress HTWCSS, traditional interlocking screws, wooden club-shaped screws and traditional screws were 131 MPa and 3.27 mm, 162 MPa and 4.07 mm, 26.5 MPa and 0.323 mm, and 34.3 MPa and 0.407 rnm, respectively. （4） These results suggest that HTWCSS has relative high bend strength, and it is able to disperse stress and improve fatigue strength bend strength, further reduce screw broken.