Table 2 Take-Home Messages

The adequate wave profile for a more effective stimulation is not clear

Studies on muscle synergies in healthy people can help determine these stimulation profiles, as well as the most appropriate muscle activations based on these wave profiles to achieve a movement as close to physiologically healthy

Implanted vs transcutaneous electrodes

The development of transcutaneous stimulation systems that use electrode arrays to achieve an adequate stimulation by means of an auto setup with virtual electrodes can promote and facilitate their unsupervised use, favoring the use of these systems compared to those that apply implanted electrodes

Daily FD neuroprosthesis use is crucial

The daily use is beneficial and the design and development of portable multichannel neuroprosthesis with auto setup seeks to increase it, as well as improve the assistance provided

Musculature stimulation strategy

The muscle stimulation of FD is mainly based on the assistance of the anterior tibial or peroneal nerve during the swing phase. However, the results of different studies suggest that the assistance of the plantar flexors is also of great importance in solving this pathology

Best sensors or sensors combination

The combination of FSRs and IMUs has been the most optimal solution in terms of gait event detection. Nevertheless, advances in gait event detection through an EEG or EMG can help in many cases to perform an adequate gait phase detection and in parallel control muscle fatigue

A reduction of muscle fatigue does not have a clear solution

The combination of CFT and VFT, the selection of an appropriate stimulation wave profile and the use of closed-loop control systems may have the potential to generate physiological movements by reducing the fatigue produced

Open-loop vs Closed-loop

Open-loop systems are very popular owing to their easy implementation, but do not solve muscle fatigue, nonlinear problems, or the variable response over time. Closed-loop control systems can be a solution. Currently, the most popular method is the ILC, because this control technique is able to provide such adaptability and applies automatic learning in a simple way; however, the systems based on an EMG and ENG present a potentially useful option if the processing difficulties, which are generated with artifacts introduced through the assistance, are solved

Closed-loop control systems still do not cross the trade barrier

Although they are a very promising solution, a suitable strategy for solving problems such as fatigue, non-linear muscle response and time variable has not yet been found.

Unilateral assistance is widespread

Regardless of the affected side, the design and development of FD neuroprosthetics and strategies that allow bilateral assistance can introduce significant advances in the search for optimal therapies for the treatment of FD

Most of the studies have focused on a biomechanical analysis, specifically kinematics

With novel advances, the combined use of biomechanical and EMG analyses can be useful to improve the understanding of the movement and the effects produced by the assistance

Systems are tested in ideal scenarios that are far removed from reality

In everyday life we find inclined planes, stairs and other obstacles, not just horizontal flat surfaces to walk on.

There is a lack of evidence of long-term therapeutic results

Most of the studies have focused on the instantaneous effect of the assistance or the effect in the short-term, and it is necessary to observe the implications of the use of a long-term neuroprosthesis for the design of personalized therapies that adapt to the evolution of the pathology

Non-progressive vs progressive diseases treatment

A different approach seems to be necessary when treating FD in non-progressive and progressive diseases. In this sense, the use of implanted systems in individuals with progressive pathologies plays an important role, although the development of systems with arrays of electrodes can be very relevant and replace them.