Page 249 - Handbook of Biomechatronics

Lower-Limb Prosthetics 245

3.1 Stability
Lower-limb prostheses should provide to the amputee stability, that is, pros-
thetic components which are not going to drive them to instability while
ambulating or provide stumbling recovery mechanisms as proposed by
Lawson et al. (2010). This is a software monitoring example that can mon-
itor and detect early stumbling and intervene. This becomes more important
in the case of bilateral transfemoral amputees where the stability needs are
higher due to inherent instabilities. The big picture or theory or biomechan-
ical model is always important. We should note the principle of conservation
of angular momentum (Herr et al., 2003) which predicts fairly well the
motion of humans during the tasks of standing and walking. It could enable
novel prosthetic devices (Herr et al., 2003).

3.2 Walking Speed
Amputees need to be able to achieve the maximum speed they can. Their
prosthesis should not be an obstacle on walking as fast as they can. It was
proposed in the past that avoidance of high-peak forces and accelerations
during gait was the reason that amputees did not achieve the maximum
speed they could (Cappozzo, 1991; Gard and Konz, 2003). Gard and
Konz (2003) also proposed that providing to the amputee the right shock
absorption will be means of improving their walking speed. Walking speed
is, therefore, connected to right shock absorption (see Section 3.4).

3.3 Socket Interface Relief of Pressure

One of the sore points that are found to present clinical problems in prosthet-
ics is the socket interface of the prostheses. Shear forces usually create high
pressure and blisters, dermatitis, and edema, which make the “symbiosis”
of amputees and conventional prostheses difficult (Mak et al., 2001). The
most radical solution to this problem is the use of the osseointegration tech-
nique (see Section 6.1) where no socket is used (Mak et al., 2001). In lieu of
using osseointegration, as mentioned in Mak et al. (2001), the computer-
aided design (CAD)/computer-aided manufacturing (CAM) technology
can make the socket design and fabrication process more effective and objec-
tive and decrease the uncomfortable effects of any nonoptimal socket
interface.