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Lower-Limb Prosthetics 269

Kuiken et al. (2017b) have proposed a novel intramedullary residual
limb-lengthening device which is less invasive than Ilizarov’s apparatus
lengthening technique and which could be used for the management of
the lower-limb amputee.

6.4 Micromechatronic Devices
Windrich et al. (2016) summarized all the active lower-limb prostheses
under research development (Table 2). The active nature of these prostheses
is at different levels as the column “Type” of Table 2 shows. For above the
knee (A/K) amputees, the emphasis is on actuators (hydraulic, magnetor-
heological, and electromechanical) that provide the right “resistance” or
impedance at the knee joint during the different phases of the gait cycle
(i.e., stance-phase knee flexion and appropriate swing leg resistance based
on step frequency during the swing phase). The variable impedance scheme
using magnetorheological liquid developed at the MIT and now marketed
via Ossur is an example of this category (see Fig. 9).
For the below the knee (B/K) amputees, there are different areas of
research as far as actuation systems is concerned: (a) series elastic actuators
(e.g., BIOM ankle, Vanderbilt transtibial prosthesis) of variable impedance,
(b) higher-level controllers which enable seamless transitions across different
states of ambulation (walking on slopes, sitting, etc.), and (c) pneumatic arti-
ficial muscles (PAM) application on actuating a BK prosthesis at the Vrije
Universiteit in Brussels, Belgium (Versluys et al., 2008).
There is research done on coordination of the prosthetic knee and pros-
thetic ankle for AK amputees, like the Vanderbilt transfemoral prosthesis
(Sup et al., 2009b) (described in Section 6.4.2) and the Cyberleg α-
prototype of the Vrije Universiteit, Brussels, Belgium (Flynn et al., 2013;
Geeroms et al., 2013).
There is also newer development at the Northwestern University con-
cerning the higher-level coordination controller and synergies of the tasks,
described in Section 6.5.
We are presenting below, representative work from the above-
mentioned newer developments.
It is important to note that there are three startups at the domain of active
prostheses: SpringActive, BionX (now OttoBock), and Freedom Innova-
tions of the Netherlands.
AsnotedinWindrichetal.(2016),thereareambiguousreportsonresultsof
active prostheses. Some show increase of walking speed and decrease of met-
abolic energy (Herr and Grabowski, 2012),butrealityis that isnewtechnology
and further studies have to be performed in order to quantify the effect.