三維下肢模擬及其於前十字韌帶損傷患者步態分析之應用

Abstract

韌帶、肌肉以及關節面間複雜的力學互動，決定了膝關節之活動度與穩定度。在膝關節之受力結構中，前十字韌帶為最容易受傷的組織之ㄧ。為了適應前十字韌帶損傷帶來的影響，患者可能會改變本身的步態型式。許多學者建立數學理論模型以研究膝關節之運動學以及力動學，但大部分為單一膝關節或膝關節以下模型，無法考慮髖關節位置對於膝關節肌肉之力量作用線方向產生的影響。本研究之目的為建立一個考慮各主要關節之三維電腦下肢模型，並以之研究行走時前十字韌帶損傷與重建患者膝關節內各受力結構之力學互動。 本研究整合一詳細的膝關節模型與一既存下肢模型。為了更準確預測動作中膝關節之肌肉、韌帶以及關節面間力量傳遞的情形，吾人發展一兩階段分析流程並與新的下肢模型完成整合。膝關節與周圍軟組織結構之運動幾何位置初始由假設韌帶不可伸長及剛性關節面的三維膝關節模型決定。藉由疊代改變關節位移分量以計算韌帶纖維與關節面受力，直到滿足平衡。 新的下肢模型已用以計算正常人、前十字韌帶損傷及前十字韌帶重建患者於步行時各受力結構之力學。結果顯示前十字韌帶損傷患者在步態站立期矢狀切面上之力矩皆為伸展力矩，此即所謂的「避免股四頭肌步態」。其於站立期前半期，腿後肌力量變大以補償前十字韌帶之功能。而前十字韌帶重建患者並沒有這種特殊的步態形式，但其股四頭肌力量與屈曲力矩均較正常人小。 未來希望能將本研究建立之下肢模型應用在其他功能性動作上，藉此模型發現臨床問題並突破目前膝關節研究之限制。

The mobility and stability of the knee joint are controlled by a complex interaction between articular surfaces and surrounding connective tissues including ligaments and muscles. Among these force-bearing structures, ACL injuries happen most often. ACLD patients may change their types of gait to compensate for ACL injuries. Several mathematical models have been applied to study kinematics and kinetics of human knee joint. However, studies on the knee joint in the literature have been based on isolated knee joint models or below knee models. The influence of the hip joint position on the lines of action of the bi-articular knee muscles has been largely ignored. The purposes of the study are to develop a three-dimensional lower limb model considering all major joints and use it to study the mechanical interactions between force-bearing structures of the knee joint in ACLD patients during gait. A detailed knee model was integrated into an existing locomotor system. A two-phase numerical procedure was developed and incorporated with the new lower limb model for better prediction of the forces transmitted in the muscles, ligaments and articular surfaces at the knee during gait. Kinematic geometry of the knee and its surrounding structures were determined initially by the three-dimensional knee model assuming inextensible ligaments and rigid articular surfaces. By iteratively changing the displacement components of the joint, the forces developed in the ligaments and contact surfaces were calculated until the equilibrium equations were satisfied. The detailed lower limb model was applied in normal, ACLD and ACLR subjects during level walking. We found the extension moment in stance phase in the ACLD subjects. It was so-called “quadriceps-avoidance gait”. In the first half of the stance phase, the hamstrings generated larger forces in the ACLD subjects, which was considered as a compensation of the ACL deficiency. This special type of gait was not found in the ACLR subjects. However, the quadriceps forces and the flexion moment in the ACLR subjects were smaller to those in the normal ones. The lower limb will be applied in different functional activities to investigate clinical problems and to overcome limitations of current knee joint studies in the future.