高位脛骨截骨手術之生物力學研究

The Biomechanical Investigations for Open Wedge High Tibial Osteotomy

駱主安(Chu-an Luo)

指導教授 ： 曾清秀 ； 林上智

國立中央大學/工學院/機械工程學系/博士(2014年)

摘要

開口式高位脛骨截骨手術是用來治療內側單側發生退化性膝關節炎，而膝關節活動度仍良好的年輕病患，其治療方式矯正膝關節已偏移的力學軸線，重新分配關節內外側的負載比例，達到減輕病患疼痛，促使軟骨再生的功效。然而開口式截骨手術難度較高，截骨矯正的過程使脛骨近端變得極不穩定，臨床上常見的失效模式包含骨釘與骨板的鬆脫或破壞，或植入物支撐能力不足使得脛骨平台斜率增加，甚至是外側脛骨斷裂導致缺口塌陷而未能達到矯正目的。
為了解決目前開口式截骨手術遭遇的問題，本研究由術前規劃開始，建立矯正角度與缺口高度之關係式，確保矯正缺口時仍能維持脛骨平台的斜率。植入物的部分以生物力學測試與電腦數值模擬的方式，研究現有單支與雙支骨板的力學傳遞與優劣，並參考分析結果，配合臨床醫師提供意見，進行新型骨板的設計。除此之外，為了簡化手術流程，提高矯正之精確性，搭配專用之截骨手術器械設計與手術流程規劃，之後利用電腦數值模擬再次驗證新型骨板的設計。因應縮短病患臥床時間的手術趨勢，本研究結合步態膝關節之力學資訊，研究截骨手術後，膝關節在步態行為下的生物力學、缺口穩定度與不利骨質癒合的受力環境。
雙支設計的骨板不論在缺口剛性、缺口穩定度與支撐強度均較單支骨板有更好的表現，步態行為下也更能降低缺口處不利骨癒合的剪力，其抗彎矩的力偶機制，能避免缺口處的槓桿效應而產生被拉伸的現象。雙支設計無可避免有較大的體積，然而選擇截骨手術固定系統時，必須在手術便利性與結構穩定性之間取捨，因此對於體重較重或有術後即下床行走需求的病患，雙支設計的骨板是較好的選擇。而單支設計的骨板配合鎖固式骨釘則適用於活動力較低且體重較輕的病患。

關鍵字

高位脛骨截骨手術 ； 骨板 ； 生物力學 ； 有限元素分析 ； 力學測試 ； 膝關節

並列摘要

Open wedge high tibial osteotomy has been used to treat osteoarthritis of the medial compartment of the knee with good mobility. This method relieves pain and stimulates the regeneration of the cartilage by correcting the incorrect biomechanical axis of the knee and redistributing the loading ratio of the tibial plateau. However, this makes the proximal tibia a highly unstable structure and causes plate and screws to be the potentials sources for mechanical failure. Other failures like the lack supporting ability of the implant to maintain the tibial slope, or the fracture of the lateral cortex.
To solve the above-mentioned problems, this study started with the preoperative planning. The mathematical formula between the correction angle and wedge height was built for maintaining the tibial slope while correcting the angle. For the implants, the biomechanical effects of one-leg and two-leg plate systems were compared by the biomechanical tests and computer simulations. A new plate is designed based on the results of the tests and simulations, and the suggestions of the clinical surgeon. Then the computer simulation was done to verify the design. On the purpose of simplifying the surgical procedure and enhancing the accuracy, the special surgical instruments were designed, and the surgical procedure was planned. Response to the trend of shortening the bed-ridden time, the current study combined the loading informations with the finite element analysis to investigate the biomechanics, wedge stability and the unfavorable situations for wedge healing after high tibial osteotomy in gait cycle.
The two-leg plates had better outcomes in wedge stiffness, wedge stability and supporting strength. Even in gait cycle, the undesired shear force at wedge was lower than the one-leg design. The two leg can form a force-couple mechanism to eliminate the bending moment, and avoid the zone of tension at the wedge tip. The choice of the plates involved the trade-off between surgical convenience and construct stability. Consequently, the two-leg system is suggested for the patients with heavy bodyweight or early weight bearing demands. The one-leg system with locking screws can be used for the majority of the patients with less activity and without heavy bodyweight.

並列關鍵字

HTO ； Plate ； Biomechanics ； Finite element analysis ； Mechanical test ； Knee

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