Osseointegration

Aadeel Akhtar visited Loyola University to give a talk about his research called “Design and Performance of an Open-Source, Affordable, Myoelectric Prosthetic Hand”. He presented the Tact hand, a prosthetic hand that is created using a 3D printer, making it affordable for individuals living in low-income countries. Many current prosthetics that are affordable only allow an individual to perform the simple function of opening and closing the prosthetic hands. Those prosthetics that have higher functions such as moving individual fingers or have a stronger grip are more expensive, costing from $25,000 to $100,000. Therefore, many people in developing countries are only able to get the basic open-close prosthetic.

Akhtar and his team were able to use a 3D printer to create a prosthetic hand which had higher functions than just opening and closing, and only costs $250. This hand is also lighter than many other prosthesis, and allows for the thumb to be manipulated in various positions. The way the prosthetic functions is by using electromyography (EMG) electrodes, which detect the movement of the muscles in the arm. Specific muscle movements will determine whether the hand will open, close, or simply move a finger much like a normal hand does.

Although Akhtar’s prosthetic hand is a great and affordable device, it is still missing one thing, sensory feedback. Being able to manipulate objects again is a huge step for individuals who have had a hand amputated. However, something that these individuals miss is the sensations they feel when they touch something. Their prosthetic hand does not let them feel the softness of a pillow, the smoothness of a marble, or the rough feeling of sandpaper. Although sensations are not necessary for performing daily functions, they do allow an individual to feel more normal and make them forget that they have a prosthetic in the first place. Well, Science Daily published an article in which scientists at Chalmers University of Technology were able to bring back sensation to amputees through the use of prosthetics. They used a technique called osseointegration in which there is a structural and functional connection between a bone and an implant.

In January of 2013, osseointegration was done for the first time, in which the patient’s prosthesis was directly connected to his bone, nerves, and muscles. This patient had his arm amputated over ten years ago and his previous prosthesis was controlled by electrodes placed over the skin. Although this gave him enough function to perform daily tasks, its functionality was limited and was quite uncomfortable. By having the artificial arm directly attach to his skeleton, the individual has better mechanical stability. His nerves and muscles work with the machine’s control systems through neuromuscular electrodes implanted under his skin. Scientists say that his technology has come a long way with having body and machine coming as one.

Through this new prosthetic, he has been able to conquer physically challenging jobs as a truck driver, performing tasks he was never able to do before. This prosthetic also allows for him to feel sensations. Since it is connected to his nerves, he is able to get information from the prosthetic to the brain. Scientists are saying that his is the first step towards a more natural artificial limb. If an amputee is able to feel sensations again, it will be as though they had never lost their limb, making them feel as normal as they were before the amputation.

The article later lists what advantages osseointegration and implanting electrodes in nerves and muscles has compared to other options. By having the osseointegration, an individual no longer has a physical limitation in their range of movement, because the limb does not have to be connected to the socket anymore. The bone also senses forces and vibrations which help in the role of sensory feedback. The prosthesis can be worn all of the time and there is no hassle of having to put it on and off. Some advantages of the implanted electrodes is that they allow for the ability of handling smaller, delicate items and more movements overall can occur. In other prosthesis, re-calibration is required daily when they put it on, but this one requires no re-calibration after the first fitting. Implanting the electrodes in the skin also means that environmental conditions such as temperature do not interfere with the control of the prosthetic. And finally, electrodes can be used to send signals to the brain that make an individual feel sensations coming from the prosthetic.

Science has come a long way in allowing people to live regular lives after injury. Now, amputees not only are able to perform normal functions with their prosthesis, but they can also start feeling sensations again. Unfortunately, the osseointegration procedure is expensive to perform to normalize that which was lost after losing a limb. However, hopefully scientists will soon discover a more affordable way of creating high tech prosthesis, such as Akhtar’s prosthetic hand.

Chalmers University of Technology. "Mind-controlled prosthetic arms that work in daily life are now a reality." Science Daily. ScienceDaily, 8 October 2014. <www.sciencedaily.com/releases/2014/10/141008153616.htm>