Bionic Prosthetics

bionic prosthesis

The term ‘bionics’ was first used in the 1960s. It combines the prefix ‘bio’—meaning life—with the ‘nics’ of electronics. Bionics is the study of mechanical systems that function like living organisms or parts of living organisms. 

Artificial limbs, or prostheses, are used to replace a missing body part which may have been lost due to trauma, disease or congenital defect. The type of prosthesis a person can use is dependent on the individual, including the cause of amputation or limb loss, and the location of the missing extremity. 

A number of bionic prosthetic limbs are now available which are beginning to mimic some of the functionality of the original lost limbs. Let’s take a look at all the options that are available.

Myoelectric Limbs

Myoelectric limbs are externally powered, using a battery and electronic system to control movement. Each prosthesis is custom made, attaching to the residual limb using suction technology. 

Once the device has been securely attached, it uses electronic sensors to detect even the smallest traces of muscle, nerve and electrical activity in the remaining limb. This muscle activity is transmitted to the surface of the skin where it is amplified and sent to microprocessors, which use the information to control the movements of the artificial limb. 

Based on the mental and physical stimulus provided by the user, the limb moves and acts much like a natural appendage. By varying the intensity of the movement of their existing functional muscles the user can control aspects such as strength, speed and grip in the bionic limb. Improved dexterity is achieved via the addition of sensors and motorised controls, thus enabling users to perform tasks such as using a key to open a door or getting cards out of a wallet.

One of the features of this technology is the ‘autograsp’ function, which automatically adjusts tension when it detects a change in circumstance (such as holding a glass that is then filled with water). An added bonus of the myoelectric limb is that, like traditional body-powered devices, it can be made to replicate the appearance of a natural limb.  

The disadvantages of this technology are that the battery and motor inside it makes it heavy, it’s expensive, and there’s a slight time delay between the user sending a command and the computer processing that command and turning it into action.


Another bionic limb breakthrough is known as ‘osseointegration’ (OI). Derived from the Greek ‘osteon’, meaning bone, and the Latin ‘integrare’, which means to make whole, the process involves creating direct contact between the living bone and the surface of a synthetic—often titanium‐based—implant.

The procedure was first performed in 1994, and uses a skeletally integrated titanium implant, connected through an opening (stoma) in the residual limb to an external prosthetic limb. The direct connection between the prosthesis and bone has several advantages: 

  1. It provides greater stability and control, and can reduce the amount of energy expended.
  2. It does not require suction for suspension, which makes it easier and more comfortable for the user.
  3. The weight‐bearing is brought back to the femur, hip joint, tibia or other bone, reducing the possibility of degeneration and atrophy that can accompany traditional prostheses.

Traditionally, the procedure requires two operations. The first involves the insertion of titanium implants into the bone and, often, extensive soft-tissue revision. The second stage, around six to eight weeks later, includes the refinement of the stoma and the attachment of the hardware that connects the implant to the external prosthetic leg. Gradually, bone and muscle begin to grow around the implanted titanium on the bone end, creating a functional bionic leg. The external prosthesis can be easily attached and removed from the abutment within a few seconds. 

Because the prosthesis is attached directly to the bone, it has a greater range of movement, control and, in some cases, has allowed wearers to distinguish tactile difference between surfaces (such as carpet versus tiles) via osseoperception.

Gait-training, strengthening and rehabilitation are all important parts of the pre and post‐surgery procedure. Many of the recipients of the new technology have been up and walking independently within weeks of the operation, and have been able to regain much of their quality of life.

A continuing development in the field of OI is the introduction of products that use a porous metal construction, such as titanium foam. Traditional OI designs intended for the femur were not successful when applied to the tibia as the proximal tibial bone structure is highly spongy. However, with the development of titanium foam technology the application of OI has now been expanded to transtibial amputees. These 3D-printed metal foams may promote and contribute to bone infiltration and the formation and growth of vascular systems within the defined area. In this way, the porous, bone‐like metal foam allows osteoblast activity to begin. 

Recipients of the OI procedure say that it almost feels like the real thing. Drawbacks of this type of prosthesis are that it is costly (generally over $50,000), and unsuitable for many types of amputees.

Mind‐Controlled Bionic Limbs

The next advance in bionic limb technology is the emergence of mind‐controlled bionic limbs. These are prostheses which can be integrated with body tissues, including the nervous system. They are highly advanced, able to respond to commands from the central nervous system and therefore to more closely replicate normal movement and functionality, while also instantly triggering the desired movement with less ‘lag time’. 

Targeted muscle reinnervation

A surgery called targeted muscle reinnervation uses nerves remaining after an amputation, and the same impulses from the brain that once controlled flesh and blood, to control an artificial limb. The surgery reattaches nerves that control the joints from the missing part of the limb into muscle tissue in the residual limb to allow a more natural thought process and control the prosthesis the same way as myo-electric control. Effectively, the brain impulses are linked to a computer in the prosthesis that directs motors to move the limb. 

The procedure involves numerous steps over many months:

  1. Targeted muscle reinnervation surgery, a procedure which reassigns nerves that once controlled the arm and hand. By reassigning the existing nerves, it becames to control prosthetic limbs merely by thinking about the action you want to perform.
  2. After recovery, patients are given training on the pattern recognition system that makes up a key part of the technology. Pattern recognition algorithms are used to identify individual muscles, how they are contracting, communicating and working with each other, as well as their amplitude and frequency. This information is then used to create the actual movements of the prosthesis.
  3. A brace was custom is created. This device supports the prosthetic limbs, while also making the neurological connections with the reinnervated muscles.
  4. Patients undertake further training on the limb system using a virtual integration environment.
  5. Finally, the limbs were attached to the brace, and patients are able to begin to putting training into practice, moving various objects.

There was also an unexpected effect in some patients undergoing this procedure: not only can they move their new limb, they can feel some sensation with it.

Implanted myoelectric sensor technology

Doctors and researchers have created a mind‐controlled prosthetic leg that uses implanted myoelectric sensor (IMES) technology. This involves sensors implanted directly into the patient’s limb muscles but, unlike nerve reinnervation, there is no need to transplant nerve tissue from one part of the body to another. Implanting the IMES technology is relatively easy and simple—requiring only a 15-minute operation where each sensor is placed into the tissue via incisions just 1 centimetre long. Once inserted, the sensors don’t need to be replaced unless they become damaged.

The technology allows the user’s experience with their prosthesis to become more intuitive and integrative. Patients no longer need to think about their movements because their unconscious reflexes are automatically converted into myoelectric impulses that control their bionic prosthesis.

It takes patients about 10 minutes to get control of the prosthesis, stand up and just walk away.

The best advantage about IMES technology is that it can be relatively simple to fit (since it does not require complex surgery), functions well in ‘real life’ scenarios and can work for an extended period of time.

The advances for our patients have made these artificial limbs more practical and intuitive, allowing them to return to their lives and expanding their capabilities even beyond what was previously possibile.

Cosmetic Improvements for Prostheses

The emergence of 3D printing and computer‐aided design is beginning to help create limbs that are a perfect custom‐fit for the wearer, and, as time progresses, are becoming more affordable.

Prostheses can now be created with anatomically correct shapes that mirror the form of the wearer, and can incorporate details such as accurate skin colour, freckles, birthmarks, hair, veins, tattoos, fingerprints and fingernails. These life-like creations can be made from PVC or a range of silicones and cover the prosthetic limb using a variety of methods, such as adhesive, stretchable skins, suction, form fitting, or a skin sleeve. For many amputees, having a limb that does not attract unwanted attention is very important and allows them to reintegrate completely in society.