Swing-phase-control knees

The fluid in these cadence-responsive knee units may be oil (hydraulic) or air (pneumatic). For hydraulic knees, the fluid is incompressible. The resistance to piston motion results from fluid flow through one or more orifices. As such, the resistance is dependent on the fluid viscosity and density, the size and smoothness of the channel, and the speed of movement. In contrast, for pneumatic knees, the fluid is compressible. The resistance is again due to fluid flow through the orifice(s) but is also influenced by fluid compression. Since air is a gas, potential leaks in pneumatic knee units will not result in soiled clothing, unlike what may occur with hydraulic knees. In addition, since air is less dense than oil, pneumatic units tend to be lighter than hydraulic units. However, since air is less dense and less viscous than oil, pneumatic units provide less cadence control than hydraulic units. Note that since viscosity is influenced by temperature, hydraulic (and pneumatic) knee units may perform differently inside and outside in cold weather climates. An example of a hydraulic cadence-responsive knee unit is the Black Max (USMC, Pasadena, Calif.). Additional examples include the Spectrum Ex (pneumatic, Hosmer, Campbell, Calif), Pendulum (pneumatic, Ohio Willow Wood, Mt. Sterling, Ohio), and Total Knee (hydraulic. Model 2000, Century XXII Innovations, Jackson, Mich.), which combine a cadence-responsive resistance swing-phase-control knee with a four-bar polycentric stance control knee. 

Swing-phase control of the knee should operate in three areas ... 

The Adaptive Prosthesis uses two microprocessor-controUed motor valves to control a hybrid hydrauHc and pneumatic system. The hydraulic system controls stance, flexion, and terminal impact. The pneumatic portion of the system control both swing phase and knee extension. The Adaptive Prosthesis also offers a... 

FIGURE 33.20 C-leg system with microprocessor-controlled hydraulic knee with stance and swing phase control. 

Another new commercial product is the 3C100 C-Leg (Otto Bock, Minneapolis, Minn.) (Fig. 33.20). This transfemoral leg incorporates a microprocessor-controlled hydraulic knee with swing and stance phase control. The controls are adjusted for the individual subject. The knee angles and moments are measured at 50 Hz, and the prosthesis facilitates ambulation at various speeds on inclines, declines, stairs (step over step), and uneven terrain. The rechargeable lithium-ion battery provides sufficient power for a full day (25-30 hours). Similar microprocessor-controlled pneumatic... 

FIGURE 45.5 C-leg. The C-leg is a transfemoral prosthesis that incorporates intelligent knee mechanism allowing controlled swing and stance phases of the gait cycle. 

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