Farber B S, Jacobson J S
Lower Limb Prostheses and Orthoses Mechanics Laboratory, Central Research Institute of Prosthetics and Prosthesis Design, Moscow, Russia.
J Rehabil Res Dev. 1995 Nov;32(4):337-48.
Knee flexion to 24 degrees during early stance transforms kinetic energy into potential energy of a total center of mass (TCM) position. Flexion is controlled by the musculoligamentous apparatus. Reproduction of such flexion in a new single-axis prosthesis knee unit has minimized the metabolic energy cost to the patient by a more favorable use of gravity acting upon the prosthetic segments and the body as well as of inertia. Potential energy is stored in the spring shock absorber of the knee unit. The coefficient of energy recovery increased by 30% in comparison with a conventional above-knee prosthesis. Energy costs to the patient decrease an average of 35% during gait with the new prosthesis. The same amount of unloading during walking is typical of an intact limb. The knee unit mechanism has a link set on the axle, thus providing two joints with a common axis: a) the main joint for knee flexion to 70 degrees during swing phase and flexion to 135 degrees during sitting; b) the second joint for bending at the beginning of stance phase. Compared with conventional units, gait with the new unit displays several functional advantages: 1) normal knee kinematics with movement of a TCM along a trajectory that contributes to an easy rollover of the foot and smooth and continuous translation of the body; 2) shock absorption during early stance prevents impact from the anterior brim of the socket; 3) at mid-stance, the increase of the TCM position accumulates potential energy that results in a significant increase of the push-off force; 4) during rapid gait, the unit provides adequate resistance to knee flexion; 5) location of the joint axis in front of the line of gravity loads the prosthesis in standing, making possible unimpeded carrying of the prosthesis over the support, the lengths of the prosthetic and the intact limb being equal; in addition, it facilitates flexion before the beginning of the swing phase. Production of the units began in 1992.
在站立初期，膝关节屈曲至24度可将动能转化为总质心（TCM）位置的势能。屈曲由肌肉韧带装置控制。在新型单轴假肢膝关节单元中重现这种屈曲，通过更有利地利用作用于假肢节段和身体的重力以及惯性，将患者的代谢能量消耗降至最低。势能存储在膝关节单元的弹簧减震器中。与传统的大腿假肢相比，能量恢复系数提高了30%。使用新型假肢时，患者在步态中的能量消耗平均降低35%。行走时相同程度的卸载是健全肢体的典型特征。膝关节单元机构在轴上设有连杆组，从而为两个关节提供共同轴线：a）主关节，在摆动期膝关节屈曲至70度，在坐姿时屈曲至135度；b）第二个关节，在站立期开始时弯曲。与传统单元相比，使用新型单元的步态具有几个功能优势：1）正常的膝关节运动学，总质心沿着有助于足部轻松翻转和身体平稳连续平移的轨迹移动；2）站立初期的减震可防止来自接受腔前缘的冲击；3）在站立中期，总质心位置的升高积累势能，导致蹬地力显著增加；4）在快速步态中，该单元为膝关节屈曲提供足够的阻力；5）关节轴线位于重力线前方，使站立时假肢负重，在假肢和健全肢体长度相等的情况下，能够无障碍地在支撑面上携带假肢；此外，它便于在摆动期开始前屈曲。这些单元于1992年开始生产。
