無股骨柄式人工髖關節之有限元素分析

Finite Element Analysis of the Cervico-Trochanteric Stemless Femoral Prosthesis

劉育良(Yu-Liang Liu)

指導教授 ： 陳文斌

中原大學/工學院/醫學工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100346

摘要

人工髖關節手術的發展中，表面置換術是較早被採用的手術方式。但是這樣的手術會在球頭以及髖臼杯有高應力的產生，造成手術的失敗，以至於最後被停止使用。不過，經由這樣的觀念，進而有無股骨柄式植入物的產生。無股骨柄式人工髖關節設計的理念就是為了要避免因傳統植入物所造成的應力遮蔽效應以及因超高分子聚乙烯磨耗碎屑掉入骨髓腔所產生的骨溶解現象。本研究的目的就是要比較新式C-T (Cervico-Trochanteric) 無股骨柄式人工髖關節及傳統PCA (porous-coated anatomic) 植入物之股骨內、外側應力及應變量分佈之差異，進而討論兩種植入物在生物力學上之特性。我們建構完整股骨模型、植入C-T植入物模型及植入PCA植入物模型等四組三維的有限元素模型。其中，也將探討以兩根螺釘及三根螺釘固定C-T植入物對其應力分佈之影響。
本次研究所建構之模型是將植入物植入人造股骨後，經由電腦斷層掃描取得其外輪廓。再經由有限元素生成實體元素，最後給予元素種類、材料性質及邊界條件等各項參數，送至國家高速電腦中心進行分析。元素種類為四面體二階元素，且將不同模型種類之元素(皮質骨、海綿質骨、鈦合金及鈷鉻鉬合金)假設為線性及彈性之材料性質。
由分析結果得知：1.C-T植入模型在股骨近端內側之蒙麥斯應力較完整股骨及植入PCA模型大。2.不論以兩根螺釘或三根螺釘固定C-T植入物模型，其應力遮蔽效應較植入PCA模型不明顯。3.以兩根螺釘或三根螺釘固定C-T植入物之模型，其蒙麥斯應力分佈情形沒有明顯的差異。4.固定C-T植入物之螺釘周圍沒有明顯的應力集中現象。
綜合以上的結果，我們發現植入C-T植入物之模型其應力分佈情形較植入PCA之模型趨近於完整股骨，且因為設計為無股骨柄式人工髖關節，除了可以有即時固定植入物之效果外，也避免了碎屑掉入骨髓腔所造成的骨溶解現象，提供臨床上一個更好植入物的選擇。

關鍵字

C-T無股骨柄植入物 ； 應力遮蔽效應 ； 全人工髖關節置換 ； 有限元素分析 ； 人造股骨 ； 骨溶解

並列摘要

Stemless-type prostheses, such as, surface replacement have been used during the early developing stage of hip arthroplasty. However, the high stresses occurred at the femoral head and the acetabulum jeopardized its development. New types of stemless prostheses were created for solving the stress-shielding effect and the osteolysis caused by the wear debris often seen in stem-type prostheses. The objective of this study is to investigate the biomechanical performance of a newly designed Cervico-Trochanteric (C-T) stemless prosthesis by comparing the stress distributions with the traditional stem-type PCA (porous-coated anatomic) prosthesis. Three-dimensional finite element models were created for the intact femur, C-T implanted femur, and PCA-implanted femur. The stress and strain distributions were compared. Also the effects of using two or three fixation screws for the C-T prosthesis were investigated.
Four finite element models were created for the intact femur, C-T implanted (with two fixation screws) femur, C-T implanted (with three fixation screws) femur, and PCA implanted femur. The geometry of the femur was based on a standardized composite femur (Pacific Research Laboratories Inc., USA). The element type used was 10-node (2nd order) tetrahedral element. Material properties for each different material (cortical bone, cancellous bone, titanium alloy, Co-Cr alloy) were considered to be linear, elastic. Loading condition of single-legged stance was considered.
The results can be summarized as: 1.Von Mises stress in the proximal, medial femur for the C-T implanted model was higher than that of the intact model and the PCA-implanted model. 2.Stress-shielding effects were significantly eliminated for the C-T-implanted models (with 2 or 3 fixation screws) as compared with PCA-implanted model. 3.No significant difference in von Mises stress distribution for the C-T-implanted model with 2 or 3 fixation screws. 4.There is no significant stress concentration around the fixation screws.
Based on the results, we found that the C-T implanted femur has more physiological stress distribution on the proximal femur than that of PCA prosthesis. C-T prosthesis can prevent the osteolysis caused by the wear debris. It can provide immediate stabilization of the implant and the preservation of endosteal vascularity.

並列關鍵字

C-T stemless prosthesis ； Stress-shielding effect ； Total hip replacement ； Finite element analysis ； Composite femur ； Osteolysis

參考文獻

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