Page 246 - Handbook of Biomechatronics

242 Georgios A. Bertos and Evangelos G. Papadopoulos

BC (Hernigou, 2013). One of the first but very functional lower-limb pros-
theses was the “peg leg,” a wooden leg that was used by military amputees and
pirates (Hernigou, 2013). Wooden peg legs have been effective prostheses for
thousands of years (Herr et al., 2003). It was not until the 20th century, with
the introduction of polymers that the lower-limb prostheses started to be built
with plastics. Currently, in lower-limb prosthesis design, we are on the verge
of a new era in which embedded microcomputer systems will take over the
automatic control of lower-limb states through the automatic control of
hydraulic and/or pneumatic-actuated mechanisms. The C-leg of Otto Bock
represents the first lower limb of this kind, although a couple of other
computer-controlled knees are available at the moment (Michael, 1999).
More legs of this kind will emerge. However, the effectiveness and efficiency
of these designs will depend on the quality of the algorithm executed, which
in turn depends on our understanding of normal and prosthetic walking.

2 HOW IS SUCCESS DEFINED FOR LOWER-LIMB
PROSTHETICS?

Success in lower-limb prosthetics is measured by the percentage of the
lower-limb amputees using their prostheses, and is functional and happy
with them (Webster et al., 2012). Human walking is a basic characteristic
of human everyday life. As mentioned in Section 4, able-bodied walking
is a repetitious and energy-efficient process. If we were to measure success,
we would expect that lower-limb prostheses would enable amputees to walk
with similar performance to able-bodied ambulators or outperform it.
Similarly, it is expected that lower-limb prostheses will enable amputees to
perform or outperform in other everyday life tasks such as running, jumping,
hopping, dancing, ascending and descending stairs, and hiking, the list goes on
depending to what is subjectively important to the amputee. Happiness is sub-
jective and personal and the same is true for success in lower-limb prosthetics.

2.1 What Would be Ideal?

The ultimate objective of lower-limb prostheses is to replace the function-
ality of the natural limb. Since the human legs are well versatile and there is
inherent redundancy, they are used for different types of locomotion and
activities, that is, jumping, running, dancing, ascending and descending
stairs, and walking in an optimal way. For each of these activities, a model
(or models or a unified model) that describes that activity is needed in order
to intervene and be able to scientifically design a prosthetic “compensatory”