重大車禍或工業意外易造成肢體開放性骨折，並伴隨硬骨骼與軟組織的撕裂傷，治療此種手術相當困難，臨床醫師常難以判斷骨骼碎片原先的位置、長度及旋轉角度。基於積層製造技術的微孔狀骨缺損植體，先前已有相關的研究探討其生物力學特性，然而，此結構設計應用於股骨遠端骨折之力學特性尚未被釐清，故本研究目的是以有限元素分析方法探討骨缺損植體之結構設計與固定策略，分別以骨螺絲與鎖定式骨板固定後於臨床三個不同階段的生物力學性能。

本研究使用 SolidWorks 繪圖，由股骨、骨缺損植體、鎖定式骨板以及骨螺絲組成，完成模型建構後將其匯入電腦輔助工程分析軟體 ANSYS Workbench 2020 R2進行模擬分析，共有 14 個模型評估骨缺損植體結構設計；有 36 個模型評估固定治療策略。數值模型考量髖關節反作用力與股骨近端臀中肌負載，最後將所有結果與正常無損傷的股骨做比較。

研究結果顯示，多孔結構的孔隙率和彈簧結構的節距均會影響股骨的形變量與骨缺損植體的應力值，其中會以孔隙率 41%的多孔結構 D 和溝槽尺寸 1 mm 的彈簧結構 F 最近似正常無損傷的股骨，此外，骨缺損植體與鎖定式骨板呈互鎖固定，在術後早期可獲得較佳的穩定度，在恢復時期可復原自身的活動範圍；骨缺損植體與鎖定式骨板呈融合固定，在術後早期亦有較佳的穩定度，但在恢復時期易造成骨板壓迫骨膜的情況，使得股骨的自由度受限，而且會阻擋血液供給養分。這項研究可被應用開發其它骨缺損植體的結構設計與固定策略，並應用於其它型式的骨缺損問題。

Repairing large segmental defects of long bones caused by major traffic or industrial accidents is still a challenging problem in orthopedic surgery. Artificial materials, i.e. titanium and its alloys performed well in clinical applications, are plenary available, and can be manufactured in a wide range of porous implant designs. Although the mechanical properties are determined, studies about the biomechanical behavior under physiological loading conditions are rare. Therefore, the purpose of this study is to investigate the structural design and fixation strategies of bone defect implants using the finite element method. The mechanical stability of the two types of scaffold designs and the two types of fixation treatment strategies were characterized under biomechanical loading within a large segmental distal femur defect of 40 mm.

The novel titanium scaffolds were designed with the porous structure or the spring structure for conforming to biomechanical properties. The implant is fixed by transverse screws at the locking plate or fusion locking plate. The pre-contoured locking plate is applied at the lateral site to secure the whole construct. A numerical model with nonlinear contact element implant-bone interfaces was constructed to perform simulations for three clinical stages under single-leg standing load conditions. The three stages were fracture healing, post-fracture healing, and locking plate removal.

The results show that the porous structure D with a porosity of 41% and the spring structure F with a groove size of 1 mm exhibit the closest biomechanical performance to the intact model and conform to the yield strength of titanium materials. In addition, the interlocking strategy of implant and locking plate can obtain better stability in the early postoperative period and restore the range of motion of the femur during the recovery period. The fusion strategy of implant and locking plate is fixed, and it has better stability in the early postoperative period. However, it is easy to cause the bone plate to compress the periosteum during the recovery period, which limits the freedom of the femur and blocks the blood supply of nutrients. The research can be used to develop the structural design and fixation strategies of other bone defect implants, and be applied to other types of bone defect problems.

1. Venkatramani, H., et al., Reconstruction of post-traumatic long segment bone defects of the lower end of the femur by free vascularized fibula combined with allograft (modified Capanna's technique). Eur J Trauma Emerg Surg, 2015. 41(1): p. 17-24.
2. Wong, K.W., et al., Patient-Specific 3-Dimensional Printing Titanium Implant Biomechanical Evaluation for Complex Distal Femoral Open Fracture Reconstruction with Segmental Large Bone Defect: A Nonlinear Finite Element Analysis. Applied Sciences, 2020. 10(12): p. 4098.
3. Conway, J.D., Autograft and nonunions: morbidity with intramedullary bone graft versus iliac crest bone graft. Orthop Clin North Am, 2010. 41(1): p. 75-84.
4. Chun, C.H., et al., Clinical and radiological results of femoral head structural allograft for severe bone defects in revision TKA--a minimum 8-year follow-up. Knee, 2014. 21(2): p. 420-3.
5. Yavari, S.A., et al., Mechanical analysis of a rodent segmental bone defect model: The effects of internal fixation and implant stiffness on load transfer. Journal of Biomechanics, 2014. 47(11): p. 2700-2708.
6. Weinans, H., et al., Sensitivity of periprosthetic stress-shielding to load and the bone density–modulus relationship in subject-specific finite element models. Journal of Biomechanics, 2000. 33(7): p. 809-817.
7. Arabnejad, S., et al., Fully porous 3D printed titanium femoral stem to reduce stress‐shielding following total hip arthroplasty. Journal of Orthopaedic Research, 2017. 35(8): p. 1774-1783.
8. Tetsworth, K., S. Block, and V. Glatt, Putting 3D modelling and 3D printing into practice: virtual surgery and preoperative planning to reconstruct complex post-traumatic skeletal deformities and defects. Sicot-j, 2017. 3: p. 16.
9. Hamid, K.S., S.G. Parekh, and S.B. Adams, Salvage of severe foot and ankle trauma with a 3D printed scaffold. Foot & ankle international, 2016. 37(4): p. 433-439.
10. Mansfield, P.J. and D.A. Neumann, Chapter 9-Structure and Function of the Hip. Essentials of Kinesiology for the Physical Therapist Assistant (Third Edition), St. Louis (MO): Mosby, 2019: p. 233-77.
11. Link, B. and R. Babst, Current concepts in fractures of the distal femur. Acta Chir Orthop Traumatol Cech, 2012. 79(1): p. 11-20.
12. King, W.E., et al., Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges. Applied Physics Reviews, 2015. 2(4): p. 041304.
13. Ryan, G., et al., Analysis of the mechanical behavior of a titanium scaffold with a repeating unit‐cell substructure. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2009. 90(2): p. 894-906.
14. Weißmann, V., et al., Influence of the structural orientation on the mechanical properties of selective laser melted Ti6Al4V open-porous scaffolds. Materials & Design, 2016. 95: p. 188-197.
15. Al-Saedi, D.S., et al., Mechanical properties and energy absorption capability of functionally graded F2BCC lattice fabricated by SLM. Materials & Design, 2018. 144: p. 32-44.
16. Razi, H., et al., Shaping scaffold structures in rapid manufacturing implants: A modeling approach toward mechano‐biologically optimized configurations for large bone defect. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2012. 100(7): p. 1736-1745.
17. Wieding, J., et al., Finite element analysis on the biomechanical stability of open porous titanium scaffolds for large segmental bone defects under physiological load conditions. Medical Engineering & Physics, 2013. 35(4): p. 422-432.
18. Wieding, J., A. Wolf, and R. Bader, Numerical optimization of open-porous bone scaffold structures to match the elastic properties of human cortical bone. Journal of the Mechanical Behavior of Biomedical Materials, 2014. 37: p. 56-68.
19. Mukhi, S.R., et al., A Novel Method to Fix Type C3 Distal Femur Fractures with Bone Defect Loss Using “Harms Cage”. Yangtze Medicine, 2017. 1(2): p. 96-103.
20. Pobloth, A.-M., et al., Mechanobiologically optimized 3D titanium-mesh scaffolds enhance bone regeneration in critical segmental defects in sheep. Science Translational Medicine, 2018. 10(423): p. eaam8828.
21. Hsu, C.-C., et al., Finite Element Analysis for the Treatment of Proximal Femoral Fracture. Computers, Materials & Continua (CMC), 2009. 11(1): p. 1-13.

22. Stolk, J., N. Verdonschot, and R. Huiskes, Hip-joint and abductor-muscle forces adequately represent in vivo loading of a cemented total hip reconstruction. Journal of Biomechanics, 2001. 34(7): p. 917-926.
23. Wang, C., et al., Finite element analysis of a Gamma nail within a fractured femur. Medical Engineering & Physics, 1998. 20(9): p. 677-683.
24. Chen, M.J., et al., Impact on periosteal vasculature after dual plating of the distal femur: a cadaveric study. OTA International, 2021. 4(2): p. e131.
25. Mehboob, H., et al., Finite element modelling and characterization of 3D cellular microstructures for the design of a cementless biomimetic porous hip stem. Materials & Design, 2018. 149: p. 101-112.
26. Emmelmann, C., et al., Laser additive manufacturing of modified implant surfaces with osseointegrative characteristics. Physics Procedia, 2011. 12: p. 375-384.
27. Karuppudaiyan, S., D.K.J. Singh, and V.M. Santosh, Finite element analysis of scaffold for large defect in femur bone. IOP Conference Series: Materials Science and Engineering, 2018. 402(1): p. 012096.
28. Lu, J., et al., A 3D-printed, personalized, biomechanics-specific beta-tricalcium phosphate bioceramic rod system: personalized treatment strategy for patients with femoral shaft non-union based on finite element analysis. BMC Musculoskeletal Disorders, 2020. 21(1): p. 1-9.
29. Seo, J.-W., et al., Finite element analysis of the femur during stance phase of gait based on musculoskeletal model simulation. Bio-medical Materials and Engineering, 2014. 24(6): p. 2485-2493.
30. Hou, G., et al., An innovative strategy to treat large metaphyseal segmental femoral bone defect using customized design and 3D printed micro-porous prosthesis: a prospective clinical study. Journal of Materials Science: Materials in Medicine, 2020. 31(8): p. 1-9.
31. Chao, P., et al., Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4 mm locking compression plate. BMC Veterinary Research, 2013. 9(1): p. 1-7.
32. Märdian, S., et al., Working length of locking plates determines interfragmentary movement in distal femur fractures under physiological loading. Clinical Biomechanics, 2015. 30(4): p. 391-396. 
33. Heyland, M., et al., Semi-rigid screws provide an auxiliary option to plate working length to control interfragmentary movement in locking plate fixation at the distal femur. Injury, 2015. 46: p. S24-S32.