Page 265 - Handbook of Biomechatronics

Lower-Limb Prosthetics 259

Fig. 11 The high intelligence prosthesis (HIP) developed by Motech is using a
magnetorheological fluid damper. (From David Carlson, J., Matthis, W., Toscano, J.R.,
2001. Smart prosthetics based on magnetorheological fluids. In: Proceedings of SPIE.)

5.2 Knee Shock Absorbers

There is a new class of prosthetic knees that provide simulated stance-phase
knee flexion. These include the Otto Bock 3R60 ergonomically balanced
stride EBS-PRO-Knee, the Total Knee 2100, and the Endolite ESK+ Knee
(Fig. 12). In these, there is a polymer spring with some inherent damping,
which provides knee flexion resistance during the early phase of the stance
phase (which is obtained through the geometrical setup and the ground
reaction force vector and the moments). These knee units appear to flex
beginning at heel contact while load is being transferred to the prosthetic
limb. The knee extends by the time midstance is reached, similar to phys-
iological knee motion in normal walking. While providing shock absorption
like the VSPs, these devices may have better simulated physiological func-
tion because they appear to have a period of activation during the gait cycle
similar to the normal physiological movement that they are designed to
replace. The 3R60 technology of the EBS-PRO-Knee allows up to
15degrees of cushioned knee flexion and a polymeric spring progressively
cushions the increase in loading that occurs as weight is transferred onto
the prosthesis. This improvement in knee biomechanics may result in
increased comfort during weight bearing and walking. Two hydraulic
cylinders—one to influence stance flexion, the other to control the swing
phase—offer a more natural gait and a high degree of stability especially
noticeable on uneven terrain (Blumentritt et al., 1997).