下肢義肢相關的生物力學

Lower Extremity Prostheses Related Biomechanics

邱佳儀(Valeria Chiu) ； 林銘川(Ming-Chuan Lin)

《台灣復健醫學雜誌》 41卷1期 (2013/03) Pp. 1-11

https://doi.org/10.6315/2013.41(1)01

摘要

從義足的生物力學來看，在足跟著地的瞬間它會先扮演吸收震盪的角色，以減少腳跟直接衝擊地面之衝量，接著要能控制好足踝蹠屈的節奏；在站立中期，義足則要協助控管小腿骨幹往前擺動的流暢性；進入足跟離地時期，義足前端必須形成一個堅硬的滾動軸心，並於足尖離地瞬間使整個身體之重心往前推進並且順利轉移到對側腳去。從義膝的生物力學來看，四聯桿義膝的生物力學較接近正常人的膝關節，吾人可從阿爾法、貝他、L、S及K等五個因子去剖析它。四聯桿義膝的瞬時旋轉中心是由兩組平行桿的延長線交集所得來的。當膝蓋伸直時，其瞬時旋轉中心位於大轉子－踝連線之前或後方（即為阿爾法因子），可以決定義膝的穩定度；也可由瞬時旋轉中心在正常膝位置之上或下（即為貝他因子），來決定義肢槓桿力臂長度及省力程度；在擺動期當膝蓋彎曲65或90度時，義肢大腿與小腿之總長度縮短多少（即分別為L或S因子），這對於趾尖離地時容不容易絆倒會有所影響；針對膝離斷義肢而言，正K值之四聯桿義膝可以協助患者在坐姿時，有效地將小腿段隱藏在大腿下方。從義肢套筒的生物力學來看，套筒與殘肢要完全接觸，才能增加承壓面積、減少殘肢水腫及增加本體感覺之回饋。近年來膝下義肢之全面接觸式套筒已漸趨近於這個理想。不同於四邊形套筒的設計，包坐骨式套筒將坐骨結節與骨支包進套筒裡，藉此產生一種骨鎖定的效應，以增進前後向之穩定度；此外，也將外側壁緊貼著股骨，迫使股骨呈內縮之位置，有利於股外展肌收縮，並增強骨盆內外向的穩定度，達到兼顧美觀且舒適之境界。

關鍵字

生物力學（biomechanics） ； 下肢義肢（lower extremity prostheses） ； 義足（prosthetic foot） ； 義膝（prosthetic knee）

並列摘要

During heel strike, a prosthetic foot must perform ground-reaction force shock absorption, and thereafter, must provide control of the smooth-rhythm plantar flexion movement. During the midstance phase, the foot must provide the controlled advancement of the tibia. During the terminal stance, the anterior part of the foot must act as a hard rocker to provide progression and roll over the toe and to allow center of gravity switching to the opposite site as the tibia advances. The biomechanics of the four-bar linkage knee simulates the motion of the actual human knee joint. It can be discussed by analyzed by five factors: alpha, beta, L, S, and K. The instantaneous center of rotation (ICOR) is the point where the line of the two links intersects by joining the shin to the thigh. When the knee is fully extended, the stability of the knee (alpha factor) can be determined by noting the position of the ICOR in relation to the trochanter-knee-ankle (TKA) line (i.e., whether it is anterior or posterior to the TKA line). The beta factor is determined by the distance between the ICOR and normal knee center, and if it is more proximal it becomes positive and consumes less energy for the prosthetic knee. The L and S factors represent the shortening effect of the four-bar linkage knee at a 65° knee flexion or at a 90° knee flexion to prevent insufficient toe clearance. The K factor represents the advantage of a more cosmetic appearance in a sitting position, especially for knee disarticulation amputees. The ischial ramus containment (IRC) socket encloses the ischial tuberosity and ramus in the socket and its design consists of the maintenance of the normal femoral adduction by extending both the medial and lateral brims quite high enough to bear the ischial ramus and the area above the greater trochanter. The medial-lateral dimension is considerably reduced, whereas the anterior-posterior dimension is increased compared to the quadrilateral socket. To effectively prevent pelvic tilt and lateral gaping and to provide enhanced medial-lateral stability, there must be adequate lateral support and the socket must be maintained as close to a normal adduction position as possibly. There must be complete contact between the socket and the residual limb to increase the contact surface to decrease pressure, prevent edema and increase proprioception. The IRC fulcrum is located near the ischial tuberosity. By shifting the fulcrum medially in comparison to the quadrilateral socket, it decreases the varus moment at the midstance phase because it is close to the ground force, indicating reduced outward movement of the femur under loads.

並列關鍵字

biomechanics ； lower extremity prostheses ； prosthetic foot ； prosthetic knee