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and/or on uneven surfaces. But, if one reviews scientific literature until that date, it is not
found any other approach different to the one of the two mentioned models.
Afterwards, during the 1950s HansMauch introduced the concept of fluid-controlled
prostheses, that later received technical and clinical support (Staros, 1964; Lewis, 1965;
Mauch, 1968). It is not coincidence the presence of commercial knees with Mauchw
cylinders since then, such as the Gaitmaster
w commercialized today by the O ¨ ssur house.
The introduction of fluid in actuators used in knee prostheses, opened new horizons
regarding the reachable performance with this kind of devices. In particular, with
hydraulic prostheses, high-resistive torques for giving the user the security and
stability required during the stance phase are possible. Also, due to the intrinsic
property of fluidness of the liquid contained in the actuator, it results that knee flexions
during the swing, and returns to the extended position before heel strike, in a more
harmonious way for a bigger number of cadences.
By the 1970s, given the development in electronics, scientists began to experiment
towards intelligent prostheses (Flowers and Mann, 1977; Darling, 1978; Grimes, 1979),
and just a decade later, without having finished the development of knee passive
prostheses, the first attempts to implement intelligent prostheses on an active version
were done (Popovic and Schwirtlich, 1988), i.e. a prosthesis in which not only the
energy dissipation at the joint is controlled, but also the power generation.
Nevertheless, all of these approaches were experimental trials, and it has been barely in
the last 15 years that electronic prostheses became real and were worldwide introduced
in the market (Dietl and Bargehr, 1997).
Once electronics made its arrival, scientific research began to grow in two
well-defined directions. On one hand, studies to carry out technical assessment of
performance of each prosthesis were done, which is evidenced in section Performance
Assessment. And on the other hand, works on control systems to be used in intelligent
prostheses were initiated, such as it is shown in section Control strategies.
A brief description of the commercial launching of intelligent prostheses is as
follows: the passive knee prostheses of the Endolite house were the ones that initiated the
intelligent prostheses era. The first one was the IPw, initially developed in 1993, and later
substituted by the IP þ w, an improved version introduced in 1995. Then this model
evolved to the Adaptive
w in 1998 (Endolite, 2006), and now a new version, the Adaptive2w
is available (Above Knee Systems – The Adaptive, 2006). At the same time, the C-Legw
was launched by Otto Bock in 1997 in theWorld Congress on Orthopedics in Nu ¨remberg,
and manufactured by the same house by 1999 (Martin, 2003; Otto Bock Microprocessor
Knees, 2007).More recently, the Rheo Knee
e by O ¨ ssur was introduced in 2001 (Rheo Knee,
2007), and today also the Power Knee
e by O ¨ ssur, an active knee prosthesis is commercially
available (Power Knee, 2007). See the evolution of knee prostheses in Figure 1.
Intelligent prostheses are featured by having an on-board microprocessor which
controls the actuator response. The actuator, in the passive ones may be a hydraulic or
pneumatic cylinder controlled by opening or closing its valves through servomotors, as
in the C-Leg (Dietl et al., 1998), or a magneto-rheological brake whose response is
modulated by the current intensity that flows through the electromagnetic circuit
associated, as happens with the Rheo Knee (Herr and Wilkenfeld, 2003). For the active
ones, counting just with the Power Knee today, it is all about electrical motors.