For some diabetic pain patients, injured soldiers, and countless others in the U.S., prosthetic devices are a part of daily life. Far from the rudimentary devices in years past, new advances in technology are helping prosthetic devices evolve to become something more than just a plastic replacement limb. These new prosthetics are intelligently designed to become a part of the user’s body and mind. Here are four advances changing the way we look at artificial limbs.

1. Bilateral prosthetic control

In the summer of 2014, a Colorado man became the first bilateral shoulder-level amputee to wear and control two prosthetic limbs simultaneously. The Johns Hopkins University Applied Physics Laboratory (APL) developed modular prosthetic limbs, and Les Baugh, a former electrician who lost both arms at the shoulder in an electrical accident, was able to control both limbs simultaneously by just thinking about the movements he wanted to make.

Baugh underwent a specialized surgery called targeted muscle reinnervation. In this surgery, nerves that controlled the arm and hand are reassigned to correspond to areas of the brain that control movement. Baugh continued to work with researchers in a virtual reality setting before trying out the new prosthetic to perform actual tasks such as lifting a cup from a counter to a higher shelf.

APL’s Courtney Moran, a prosthetist working with Baugh, focused on common tasks but was surprised at how quickly Baugh was able to perform them:

“This task simulated activities that may commonly be faced in a day-to-day environment at home. This was significant because this is not possible with currently available prostheses. He was able to do this with only 10 days of training, which demonstrates the intuitive nature of the control.”

2. Artificially intelligent prosthetics

The Cognitive Neuroscience Society (CNS) is highlighting work on new prosthetics that are artificially intelligent. These prosthetics are able to take what the user does and adapt by combining previous actions and signals from the brain to predict what the device should do next. This results in movements that mimic natural neuromuscular actions.

José del R. Millán began his work by designing artificially intelligent robots to help disabled people. He then wondered if it was possible to make this assistance more intuitive by tapping into the person’s neural patterns and pathways. He designed brain-computer interfaces (BCIs), a system that allowed people to use their own brains to control and direct actions like grasping and movement.

As with the bilateral shoulder prosthetics, wheelchairs and limbs with this system can be controlled by the user’s thoughts. The goal is to make the movement or action simultaneous to the thought, more like a natural limb’s response. Moving forward, this will become autonomous in such a way that a user will be able to perform these actions without consciously thinking about them.

Millán notes that this is not a fantasy. The question is no longer “if” but “when”:

“Future neuroprostheses — robots and exoskeletons controlled via a BCI — will be tightly coupled with the user in such a way that the resulting system can replace and restore impaired limb functions because it will be controlled by the same neural signals as their natural counterparts. This is no longer science fiction; the questions now are which are the key components to guarantee reliability and long-term operation of neuroprostheses, and when they will part of the clinical portfolio available to motor-disabled people.”

3. Bionic hands

A team from the University of Houston is also using the power of the mind to develop prosthetics that are controlled only by a person’s intentions. Jose Luis Contreras-Vidal, a neuroscientist and engineer at UH, and his team used non-invasive brain monitoring to record brain imagery and then help a 56-year-old man with an amputated hand to grasp a bottle and a credit card. The patient donned a cap that measured electrical impulses in the brain through the scalp.

This technique has similar success rates to surgically implanted electrodes or myoelectric control but with one significant difference: this non-invasive brain-machine interface does not require that neural activity from muscles remain intact. Some patients who lose a limb due to trauma also have significant nerve damage that makes implants unsuccessful.

The researchers noted that with a brain-machine interface, the user may have access to more delicate and fine motor skills that an implant may struggle with.

“Current upper limb neuroprosthetics restore some degree of functional ability, but fail to approach the ease of use and dexterity of the natural hand, particularly for grasping movements. Further, the inherent risks associated with surgery required to implant electrodes, along with the long-term stability of recorded signals, is of concern. … Here we show that it is feasible to extract detailed information on intended grasping movements to various objects in a natural, intuitive manner, from a plurality of scalp EEG signals.”

4. Prosthetics with feeling

An important part of the human experience – touch – is lost along with the limb. Even the brain can remember the sense of touch long after the limb is lost, sometimes manifesting itself as phantom limb pain. In a review presented by American Society of Plastic Surgeons member surgeon Paul S. Cederna, MD, of University of Michigan, Ann Arbor, and colleagues, that lack of touch may be changing in prosthetics.

Current prosthetic advances allow the user increasingly fine motor control but still force them to rely on vision as the primary sensory experience. Researchers are looking for ways to bring touch to the prosthetic so that use of the new limb can be more natural and intuitive. Upper limb loss can be particularly traumatic, especially as it most frequently occurs among young people. Dr. Cederna and his colleagues found that restoring a sense of touch could have tremendous psychological benefit.

“The ultimate goal is to develop a prosthesis that closely mimics the natural limb, both in its ability to perform complex motor commands and to elicit conscious sensation.

[These newer techniques to do that] represent the wave of the future, paving the way to more intuitive prosthetic control through sensory feedback.”

Which development in the evolution of prosthetics is most exciting for you?

Image by Derek Bridges via Flickr