Page 235 - Control Theory in Biomedical Engineering

216 Control theory in biomedical engineering

location) increase with the level of amputation while the number of sites
available for EMG adquisition decreases (the muscle normally involved in
the function of the limb that has been lost is used as the control source).
In this sense, medical pre-procedures to relocate and amplify terminal nerves
and muscle signals that were lost after amputation are a good option to
increase the functionality of prostheses where high-level amputations are
identified.

4.4.2 Targeted muscle reinnervation
Although a limb is lost with an amputation, the control signals remain in the
residual peripheral nerves of the amputated limb. Thus, instead of surface
EMG detection, another method exploiting the residual nerves was the
development of intramuscular direct connections of a device to remaining
terminal nerves in order to increase the robustness of the control of upper-
limb prostheses (Dewald et al., 2019). This work is encouraging, but several
inherent problems appear when it comes to high-level amputations. The
neuroelectric signal is very small (microvolts), difficult to record in a long
term, and difficult to separate from the EMG signals of surrounding muscle
(which have similar frequency content). Nerve atrophy (Upshaw and Sink-
jaer, 1998), electrical components’ durability, and good electrical signal wire
transmission should be maintained. Kuiken (2006) proposed a method to
avoid these disadvantages by means of targeted reinnervation. “Targeted
motor reinnervation enabled to denervate expendable regions of muscle
in or near an amputated limb and transfer residual arm peripheral nerve end-
ings to these muscles.” A basic scheme of targeted reinnervation of a trans-
humeral amputee is shown in Fig. 2.
The extension of Kuiken’s work (2007) was presented in a case study of a
woman with a left arm amputation at the humeral neck, with great outcomes
(better intuitive prosthesis control and maneuverability) using box-and-
blocks tests (Mathiowetz et al., 1985). In other studies (Miller et al.,
2008) box-and-blocks tests and clothespin tests show from two to six times
better outcomes in high-level amputees (i.e., trans-humeral, shoulder
amputations), and then proposed techniques for targeted muscle reinnerva-
tion presented in (Cheesborough et al., 2015; Kuiken et al., 2017). In addi-
tion to the greater outcomes found with Targeted Muscle Reinnervation in
the sense of dexterity and intuitive prostheses control, other promising
results were found recently in the field of Neuroma and Physical Phantom,
presenting reduction in residual limb pain and phantom limb pain
(Dumanian et al., 2019).