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Rehabilitation Practice and Science

Translated Title

下肢義肢相關的生物力學

Abstract

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.

Language

Traditional Chinese

First Page

1

Last Page

11

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