A complete guide to bionic arms and hands

Child with a white bionic arm

We’ve partnered with Bionics For Everyone to bring you everything you need to know about bionic arms and hands, including detailed descriptions of all the current technologies and the latest research. Here, Bionics for Everyone shares its insight and knowledge, making it your one-stop repository for information on upper-limb bionics.

What is a bionic arm?

A bionic arm is an electromechanical device that attaches to the human body and replicates the functionality of a natural arm/hand.

It always consists of a bionic hand or partial hand and, depending on the level of amputation, may also include a powered wrist, elbow, and/or shoulder.

For example, here are the three configurations available for the Luke Arm System from Mobius Bionics:

Luke Arm System Configuration Diagram

Note, this particular line of devices always includes a powered wrist but this is optional or not available for other devices. Also, in some use-cases, the hand may be replaced with a powered hook or clamp.

How bionic hands function

This section is intended to teach you the limits of bionic hand dexterity. The best way to do this is to briefly describe the mechanical design of the fingers and work backwards.

The core mechanical function of a human finger is to open and close. This is replicated in a bionic finger using a design like this:

Actuated Finger Design Diagram

Source: https://doi.org/10.1016/j.ohx.2020.e00100

A battery-powered motor drives a gearing system to move the main MCP joint, which then moves the second and third joints via a bar linkage system. Note, there are many variations of this, such as using pulley systems to simulate tendons instead of bar linkage systems.

The key feature in this type of design is that there is typically only one independent joint: the MCP joint (main knuckle). The other two joints automatically follow that joint’s lead, producing the following fixed pattern of motion:

Bionic Finger Range of Motion Medium Diagram

Source: https://doi.org/10.1016/j.ohx.2020.e00100

By comparison, natural fingers can move the middle or PIP joint independently and the DIP joint quasi-independently. Additionally, natural fingers can spread out and twist and turn in a myriad of combinations.

The movement of a natural thumb is even more challenging to duplicate. In addition to opening and closing, it can rotate down and slightly outward to touch the entire underside of any finger and even parts of the palm. This allows natural hands to grasp objects of any shape.

Here is a diagram of a bionic thumb from the early work on one of the more recent entries into the bionic hand market, the Psyonic Ability Hand.

Bionic Thumb Design

Despite its mechanical complexity, this type of thumb still has many limitations. Yes, it can position itself to become an opposable force for many grips but it lacks the exceptional dexterity of a natural thumb.

This exemplifies one of the main points of this section: bionic hands are impressive feats of engineering but they are much simpler than natural hands. In one respect, this hardly matters because they can still perform a wide variety of tasks, as demonstrated in this video:

However, do not expect them to match the dexterity of natural hands. A better way to assess a bionic hand is its usefulness, which is determined mostly by its user control system.

User control systems on bionic hands

When you move a natural limb, your brain sends nerve signals to the muscles, which in turn move the limb.

When a limb is amputated, the brain still sends these signals even though some of the muscles are no longer there to receive them.

The general concept behind bionic user control systems is to intercept the brain’s signals and convert them into commands for the bionic device.

There are multiple ways to do this for bionic arms & hands. For a quick overview of control system options, see bionic hand control systems. For details on each option, click the relevant link below:

Whatever you do, do not neglect this subject. User satisfaction levels depend almost entirely on selecting the right control system.

Current below-the-elbow bionic arms and hands

Deus Arm Covers Black

Available below-the-elbow bionic arms and hands

The following is a list of the models for below-the-elbow bionic arms and hands either already on the market or soon to be (presented alphabetically). Each links to its own page for more specific details:

All of these hands offer myoelectric direct control systems at a minimum. Those sold as components (i.e. where the hand is designed to be a component of a bigger system) can also be used with pattern recognition control systems.

We do not know of any commercial bionic hands currently being used in combination with a true neural interface, though there is nothing that prevents a component hand from doing so.

Cost of below-the-elbow bionic arms and hands

Of the bionic hands currently on the market, the most affordable are the TrueLimb from Unlimited Tomorrow, the Hero Arm from Open Bionics, and the Zeus Hand from Aether Biomedical.

In their simplest configuration (least complicated residual limb), the final price for these three devices can range from £8,000 to £15,000, including prosthetist fees, where applicable.

By comparison, the most expensive hands can cost more than £60,000.

For more information, see our bionic hand price list.

Current partial hand or finger options

Partial Hand Prosthesis Four Options

Nearly 2/3 of upper-limb amputations involve finger or partial hand loss. This equates to millions of people around the world who are missing fingers, parts of fingers, or a part of their palm.

Both Ossur and Vincent Systems have created excellent bionic partial-hand prostheses but these are not well-suited for heavy loads or challenging environments. They’re also quite expensive. To address these deficiencies, our list of articles on partial-hand devices includes the best non-bionic (i.e. strictly mechanical) options:

In keeping with our goal of helping you stay informed, we have also created a current partial hand prosthesis options summary page.

Current above-the-elbow bionic arms

In general, the further up the arm an amputation occurs, the more complex the requirements for a bionic prosthesis.

This is due in part to the need for additional moving joints. But weight and power consumption also increases, as does the requirement for a stronger attachment to the residual limb or body.

Solving these problems required a bigger budget and more technical collaboration.

Enter the Defense Advanced Research Projects Agency (DARPA). In 2006, the agency launched its Revolutionizing Prosthetics program.

The goal of this program was to develop a bionic arm to dramatically improve the quality of life for upper-limb amputees. They wanted an arm capable of mimicking the natural arm and hand movements for any level of amputation.

Two advanced bionic arms resulted from this program.

The LUKE Arm

The LUKE Arm was developed for DARPA by DEKA Research and Development Corporation.

In 2014, the FDA approved the arm for commercial use:

As you can see in the video, the arm clearly fulfils its original goal. It can indeed mimic most natural arm and hand movements. In the preceding video, the wearer uses foot controls like joysticks to manipulate the arm.

However, myoelectric direct control and pattern recognition systems can be used here, too.

We have not yet been able to find any instances in which a patient is using the Luke Arm in combination with a true neural interface, as most of this work is still occurring in the lab.

Modular Prosthetic Limb (MPL)

The Modular Prosthetic Limb (MPL) was developed for DARPA by Johns Hopkins University (JHU). This is a more complex hand/arm system designed to “test direct neural control of a prosthesis”.

It has since made its way out of the lab and into home trials.

As the video demonstrates, the ability to manipulate this arm via thought is quite sophisticated. But it still isn’t as good as a natural arm/hand.

Ottobock’s DynamicArm

Ottobock has offered the DynamicArm for sale since late 2009. Although its technical origins are not entirely clear, it appears to be an above-the-elbow version of the myoelectric arms that have become so popular for below-the-elbow amputees.

Put another way, it is a highly effective bionic arm for the above-the-elbow amputees but it does not have the sophistication of either the LUKE arm or the MPL. Here it is in action:

Cost of above-the-elbow bionic arms and hands

The big problem with above-the-elbow bionic arms is cost. The LUKE Arm costs as much as £100,000. The cost for the MPL, should it get to market, will likely be similar. Even the DynamicArm, commercially available for over a decade, is still around £60,000.

Unfortunately, this price tag exceeds the budget of most amputees. However, we should not be discouraged by this. It takes a while for new technologies to trickle down into the broader market. And then it takes even longer (i.e. the effect of market forces) to significantly reduce costs. We just have to do what we can to accelerate these processes.

In the interest of accuracy, both the LUKE Arm and the MPL are not strictly above-the-elbow prostheses. Their modular design allows them to be used for all levels of upper-limb amputation.

By Bionics For Everyone

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