珈瑪骨釘(Gamma nail)已廣泛的應用於治療股骨近端骨折，其優點為(1)有較好的生物力學表現，可使病患提早下床承受自身重量並進行復健。(2)失血較少。(3)發生併發症和感染的機率較低，然而，臨床上研究仍發現植入物在治療過程中會有彎曲破斷(bending breakage)、骨切(cut-out)、鬆脫(loose)等失效問題，造成病人二次傷害。
為了減少珈瑪骨釘發生失效的機率，本研究將對珈瑪骨釘的一些改良與設計進行探討，而由於之前尚未有研究探討改變遲滯螺絲上的螺絲參數對珈瑪骨釘破壞的影響，因此本研究將改良設計的重點參數放於遲滯螺絲上的螺紋，且也尚未有研究同時考慮彎曲強度、骨切強度、骨咬合強度*的最佳化，所以本研究目的是以彎曲強度、骨切強度、骨咬合強度為目標設計出最佳化的珈瑪骨釘。
本研究先以田口直交表設計出二十五組參數不同的模型，再以SolidWorks建構出三維立體模型，並以有限元素法軟體-ANSYS Workbench 模擬分析模型之彎曲強度、骨切強度及骨咬合強度。接著使用變異數分析(ANOVA)來研究彎曲強度、骨切強度及骨咬合強度之設計參數的貢獻度，並且以田口參數化分析找出三種失效模式之最佳設計。最後再以遲滯螺絲之von Mises應力、反作用力及骨折處分離角度為目標產生類神經網路模型，並以遺傳演算法找出最佳設計之珈瑪骨釘。
田口品質工程法中參數化分析結果顯示，遲滯螺絲之螺紋長度同時為影響彎曲、骨切、骨咬合強度的重要參數，而螺紋長度之最佳設計水準，在彎曲與骨切強度為最小的10 mm，但在骨咬合強度為最大的30 mm。本研究使用類神經網路及遺傳演算法所找出之最佳設計參數是在權重值Wc = 0、Wp = 0.5、Wb = 0.5的情況，最佳設計參數為：遲滯螺絲之螺紋長度為19.03 mm，外徑比為上根外徑7.94 mm、下根外徑8.06 mm，節距為3.39 mm，近端螺牙傾角為20度，近端根部弧角半徑為0.1 mm，遲滯螺絲距為7 mm。本研究結果可以幫助工程師設計出同時兼顧彎曲強度、骨切強度與骨咬合強度的珈瑪骨釘及幫助醫師依據病人的狀況選擇合適的植入物。

Gamma nails have been used to treat proximal femoral fractures because of the advantages of immediate weight bearing capability, low blood loss, low infection risk, and shorter operating time. However, they still have the clinical complications such as screw breakage, screw cut-out, and screw loose.
In order to reduce the failure rate, this research discussed the different designs of the gamma nail. There is no research to discuss the influence of the lag screw designs of gamma nails for the bending strength, the pull-out strength, and the cut-out strength. Thus, the purpose of this research was to find the optimal factors of gamma nails considered the bending strength, the pull-out strength, and the cut-out strength.
Based on L25 orthogonal array, 3D models were created by using SolidWorks, then transformed into ANSYS Workbench to simulate the bending strength, the pull-out strength, and the cut-out strength. Analysis of the variance (ANOVA) was used to find the contribution of design factors, and the optimal combination of the lag screw was also obtained. Finally, the artificial neural network (ANN) models of the lag screws were developed to predict the von Mises stress, the reaction force, and the bone fracture separating degree. The optimal design of gamma nail would be obtained by using the genetic algorithm (GA).
In the parametric analysis of this research, the thread length of the lag screw was the most important factor in the three types of the failure modes. The optimal design for the thread length of the lag screw in bending and cut-out strength was 10 mm, but in pull-out strength was 30 mm. We found that the optimal design using ANN and GA were 19.03 mm for thread length, 7.94 mm for outer diameter of upper lag screw, 8.06 mm for outer diameter of lower lag screw, 3.39 mm for pitch, 20 degree for proximal half angle, 0.1 mm for proximal root radius, 7 mm for distance of two lag screw. In addition, the optimal design was in the situation for Wc = 0, Wp = 0.5, Wb = 0.5. The findings of this research can help surgeons select suitable implant for their patients and assist engineers developing better implants.

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