全人工髖關節幾何形狀及固定方式對於股骨近 端應力遮蔽之影響研究

The Effect of Geometry and Fixation Modes of Total Hip Prosthesis on the Stress Shielding of Proximal Femur in Total Hip Arthroplasty

戴金龍(Ching-Lung Tai)

指導教授 ： 陳文斌 ； 施俊雄

中原大學/工學院/醫學工程研究所/博士(2005年)

https://doi.org/10.6840/cycu200500134

摘要

中文摘要
由於人工關節設計、生醫材料及手術技術的進步，全人工髖關節置換手術已廣泛應用於髖關節的重建，但人工髖關節股骨柄的鬆脫始終是影響術後人工關節使用壽命的主要因素。鬆脫現象發生的誘因頗為複雜，其中應力遮蔽效應及骨質溶解，被認為是造成力學鬆脫的主要因素。人工髖關節股骨柄幾何形狀及骨水泥固定方式對於術後股骨表面應力遮蔽及骨質流失的影響始終是骨科界無法定論的議題。此一現象，由目前種類繁多的人工髖關節設計及不同的手術固定方式，即可得知。針對上述議題，以往雖有甚多文獻分別以各種不同的方法加以探討，但是結果分歧，仍無明確結論。再者，至目前止，仍然未見有相關文獻同時以體外力學測試、有限元素分析及病患臨床追蹤等三種方法系統化分析比較上述議題，獲致可靠結論。
本研究的目的，乃是結合體外力學測試、有限元素分析及病患臨床追蹤等三種不同的方法，系統化探討全人工髖關節股骨柄幾何形狀及骨水泥固定方式對於術後股骨表面應力遮蔽及骨質流失的影響，並進而設計一新型無柄式人工髖關節，探討其力學優異。研究的方法，在股骨柄幾何形狀的探討方面，是選定兩種不同幾何形狀的C-fit對稱型及PCA解剖型股骨柄，在無骨泥固定情況下植入人造股骨，分別量測二者術前及術後股骨表面應變的差異；在臨床的追蹤上，則選定以無骨泥方式植入上述兩種人工髖關節之病患，利用雙能量骨密度測定儀，以回顧方式來評估二者術後骨質密度流失的差異。至於骨水泥固定方式的探討方面，則是選定C-fit對稱型股骨柄，分別以無骨水泥固定、股骨柄上端外圍骨水泥固定及股骨柄外圍全部骨泥固定等三種不同固定方式植入人造股骨，以有限元素法探討三者間術前及術後股骨表面應力分佈的差異；在臨床的診斷上，則選定以上述三種不同固定方式植入C-fit對稱型股骨柄之病患，以前瞻方式來評估三者於術後兩年內骨質流失的差異。此外，為根本解決傳統有柄式人工髖關節所無法克服的應力遮蔽及骨質流失現象，本研究自行設計新型無柄式人工髖關節，分別藉由體外力學測試（應變量測及動態破壞測試）及有限元素分析來比較此新型人工髖關節與傳統式PCA解剖型人工髖關節於植入股骨後，二者間應力遮蔽的差異性。
研究結果顯示，體外力學測試、有限元素分析及病患臨床追蹤等三種不同方法均獲得一致結果。其中，在股骨柄幾何形狀的探討方面，體外力學測試及回顧式臨床追蹤均顯示：PCA解剖型股骨柄相較於C-fit對稱型股骨柄，將造成較嚴重的應力遮蔽及骨質流失現象。此外，在骨水泥固定方式的探討方面，有限元素分析及前瞻式臨床追蹤則顯示：無骨水泥固定方式將造成最嚴重的應力遮蔽及骨質流失現象。骨水泥的添加，有助於改善應力遮蔽及骨質流失，其中又以股骨柄上端外圍骨水泥固定所造成之應力遮蔽及骨質流失最為輕微。最後，體外力學測試及有限元素分析則有效證實自行設計之新型無柄式人工髖關節於植入股骨後，其應力、應變分佈狀態趨近於正常股骨，可有效消除應力遮蔽效應。
結論，在股骨柄幾何形狀及骨水泥固定方式的六種組合中，以無骨水泥固定方式植入PCA解剖型股骨柄，將造成最為嚴重的應力遮蔽及骨質流失現象。加入骨水泥有減輕應力遮蔽，使術後股骨獲得較接近於正常股骨之應力、應變分佈的趨勢，改善應力遮蔽及骨質流失現象。此外，新型無柄式人工髖關節可獲得最為趨近正常股骨之應力、應變分佈，且具備防止磨耗粒滲入骨髓腔、易於再次手術……等諸多優點，是取代傳統有柄式人工關節的理想植入物。

關鍵字

體外力學測試 ； PCA解剖型股骨柄 ； 應力遮蔽 ； 骨水泥 ； C-fit對稱型股骨柄 ； 臨床追蹤 ； 有限元素分析 ； 無柄式人工髖關節

並列摘要

ABSTRACT
Surgical reconstruction of the hip with total joint arthroplasty has proven to be a successful surgical procedure due to the improvements of prosthetic design, biomaterials and surgical technique. However, the success of the surgery it is limited by the mechanical failure of stem loosening. Stress shielding and osteolysis are considered to be the main factors causing loosening. Until now, the influence of stem geometry and fixation modes on stress shielding and bone loss remains controversial. Numerous investigations have been done to examine the stress shielding and adaptive bone remodeling following total hip arthroplasty. All the results have indicated that, in actual applications, the addition to the femur with any stem-type implant would cause certain degree of stress shielding. However, the effects of stem geometry and the bone cement on the degree of stress shielding still remains controversial. To date, although a number of researches have been done on the related topic, however, it lacks an integral approach, an integration of in vitro experiments, simulated stress analyses and clinical evaluations, to examine the above-mentioned problems.
This study systematically conducted a tripled approach involving experimental measurement, finite element analysis and clinical follow-up to examine the stress shielding and bone loss following total hip arthroplasty. There are three objectives in this study; the first objective is to investigate the influence of stem geometry (straight or curved) on the degree of stress shielding. The second objective is to investigate the effect of cement in different fixation configurations on the degree of stress shielding, and the third objective is to develop an ideal stemless cevico-trochanteric (C-T) stem to avoid the stress shielding and bone loss that the conventional stem-type prosthesis encountered. In the exploration on the role of stem geometry, the straight (C-fit) and curved (PCA) stems with cementless fixation were examined. Strain measurement was performed using synthetic femur before and after stems insertion, and the surface strains were compared between two groups. Besides, a randomized retrospective analysis was also conducted using Dual-energy X-ray absorptiometry. Periprosthetic bone mineral density for patients who underwent straight and curved stems replacement was measured and compared. In the exploration on the role of cement fixation, C-fit stem implanted with three different configurations of cement fixation (cementless, proximally-cemented and fully-cemented) were compared using finite element analysis. An additional prospective follow-up was also conducted for patients who underwent total hip arthroplasty with C-fit stem by cementless, proximally- and fully-cemented fixations. Finally, in the exploration on the newly designed C-T stemless prosthesis, static tests with strain measurement combined with cyclic tests up to failure were performed to evaluate the mechanical characteristics of this new stemless prosthesis.
The results of in vitro test and finite element analysis are well corresponding to those of clinical follow-up. The results indicated that the curved PCA stem induces more stress shielding and causes a more significant bone loss as compared to those of straight C-fit stem. Furthermore, stem implanted with cementless fixation experienced the most significant stress shielding and bone loss as compared to those of either proximally- or fully-cemented. The application of bone cement tends to decrease stress shielding and normalizes the proximal femoral stress. Additionally, the C-T stemless prosthesis exhibited a more physiological stress distribution as compared to those of the traditional stem-type prosthesis. We concluded that, in the six combinations of stem geometry and fixation modes, curved stem combined with cemented fixation would induce the most stress shielding in doing hip replacement. The C-T implanted femur has more physiological strain distribution and satisfactory interfacial bonding with cement fixation.

並列關鍵字

Bone cement ； Stress shielding ； C-fit straight stem ； Stemless hip prosthesis ； Finite element analysis ； In vitro test ； PCA curved stem ； Clinical follow-up

參考文獻

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