Finite element analysis of mechanical properties of wooden club shaped and general screws with interlocking intramedullary nail

[Purpose] Aiming to evaluate the mechanical properties of wooden club shaped screw (WCSS), and provide theoretical basis for its clinical application, we analyzed mechanical properties of two different locking screws of interlocking intramedullary nail (IIN) via three-dimension (3D) finite element method. [Methods] Acquire tibia CT images of adult using spiral CT scanning. Utilize related software such as Mimics, Geomagic Studio and Pro/E to establish 3D solid models of tibia, two different locking screws and intramedullary nail, to assemble two different models of locking screws into intramedullary nail and tibia, and to simulate a solid model of middle tibia transverse fracture. Apply loads on two different models respectively, simulate the conditions of tibial plateau subject to four different loads, and analyze the mechanical properties of WCSS and general screws. [Results] On the condition of four different loads, both the axial displacement and the maximum stress of IIN model with WCSS were smaller than that of the model with general screws. The average value of the axial displacement and the maximum stress respectively were 2.65mm and 102.443MPa in the model of IIN with WCSS, while they were 3.23mm and 135.798MPa in the model of IIN with general screws. And those were 2.46mm and 62.914MPa in the model of WCSS, while those were 3.02mm and 88.754MPa in the general screws. The stress was dispersed on WCSS model, while it was concentrated on general screw model. [Conclusion] Comparing with general screws, WCSS had more dispersed stress, stronger anti-fatigability, higher bending strength, and better stability for IIN on the condition of applying the same loads.