Prosthesis

Basic overview and Advancements

Intro

The first thing people think of when they hear prosthesis is someone who has lost an arm or a leg. But its not always arms or legs, it can be ears, eyes, noses, fingers, or toes. Injury ,disease, or a birth defect can cause someone to not have a limb or body part.
Eye prosthesis information video

History

In 2000 researchers in Cairo, Egypt discovered the oldest documented artificial body part. A prosthetic toe made of wood and leather. The device was found attached to mummified remains of an Egyptian noblewoman that is nearly 3,000 years old. The device shows a good representation of how little prosthetic limbs have changed through history.In the 16th century a French military doctor, contributed some of the first major advances in prosthetics seen in many years. He invented a hinged mechanical hand, as well as prosthetic legs that featured advances like locking knees and specialized attachment harnesses.
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Advancements

It is difficult to get a prosthesis made of sensors and metal to mimic human movement. Since around 2005 the Rehabilitation Institution of Chicago (RIC) has been working on a method that is called muscle reinnervation, which takes nerves from an amputated limb to healthy muscles. But despite many advances the functionality of prosthetic limbs remain limited. Although a technique was developed by many researchers, and it primarily bonds titanium to bone in the arm.

Titanium Bonds

Because of the high dieletric constant, titanium has the property to bind to bone and living tissue. Because of this, these implants will last longer than when made of material that need adhesives.

Modern prosthetic Limbs

Modern prosthetic limbs are made of newer materials such as advanced plastics and carbon-fiber composites. These materials make the limbs lighter and stronger. Electronic technologies make advanced prosthetics capable of automatically adapting to their function ( i.e. gripping and walking). It also makes them more controllable.


The pylon is the internal frame or skeleton of the prosthetic limbs. The pylon must provide structural support and traditionally has been formed of metal rods. But more recently, they have been made of lighter carbon-fiber composites that have been used to form the pylons.


The socket is the portion of the prosthetic device that interfaces with the patient's limb stump or residual limb.Because the socket transmits forces from the prosthetic limb to the patient's body, it must be carefully fitted to the residual limb to ensure that it doesn't cause irritation or damage to the skin or underlying tissue.


The suspension system is what keeps the prosthetic limb attached to the body. The suspension systems can come in several different forms. For example in case of a harness system straps, belts, or sleeves are used to attach the prosthetic limb.

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Myoelectric prosthesis

"Myoelectric" is the term for electric properties of muscles. A myoelectric controlled prosthesis is an externally powered artificial limb that you control with the electrical signals generated naturally by your own muscles. It uses the existing muscles in your residual limb to control its functions. Multiple sensors are added into the socket and they receive the electrical signals when you intentionally engage specific muscles in your residual limb. The sensors relay the information to a control and that controller translates the data into commands for the electric motors that move your joints.The strength and speed of the movements can be controlled by varying muscle intensity. But if people have nerve or muscle damage in their residual limb, or have no arms, muscles in the chest or back can be used to direct the movements.
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Improving fit and function for hip disarticulation

Only 1-2% of prosthetic patients have this type of amputation. This involves leaving a very small portion o the femur or hip socket. This kind of amputation is not common so many prosthetists never see that in their entire careers. But for the ones who do, they don't what they can do for the person. One 1983 study shows that 25% of all hip disarticulation patients use a a prosthesis, of those many ended up abandoning it because it was to uncomfortable and difficult to use.


Working toward a new solution

One reason that there weren't many advancements in the past was because manufacturers didn't really have a reason to invest. Also because people with hip disarticulation make up so little of the population of people with prosthesis, there is not enough demand for products created for specific needs. "The prosthetics industry is not going to put too much money into this because the numbers are too minute" Says Stan Patterson,CP, founder of Prosthetic & Orthotic Associates of Central Florida (POA).

Interview with Master Sergeant Bergom

Master Sergeant Bergom fits prosthetic limbs and helps them with their new limbs.


How do you fit the prosthetic limb to the person?

Below the knee is the most common amputation . A lot of factors go into how you fit the person with the limb. It depends on how long the person has been an amputee. If they haven't had their limb for a few months it is easier to have it fit. But if they just had the amputation it is harder to fit and you have to wait to fit it because there is swelling and the fresh incision. And if the person does not elevate their stump the tendons will shorten and it will take longer for the swelling to go down. It also depends on the health of the person.

You have to have a lot of measurements. You take measurements of the leg that was not amputated just to get a baseline of what the leg should be close to. Then every inch or two inches of the remaining leg. You also need to measure how long the leg is. This lets you know a few things. How long you need to make the prosthesis and also so you know what kind of components to put between the foot and the bottom of the leg.


How long after the surgery or injury will you be able to fit the person with the prosthesis?

Again it also depends on the health of the person. For some it could be as little as two weeks and others it could take over a year. While they are preparing to be fit with the prosthesis they will have to have a to work on stretching exercises, keeping a rigid dressing on, keep an ace bandage around their stump so it will help the swelling, and general good skin care. They will also have to work on desensitizing the leg by patting it or massaging it when the incision when it is stable. But when it is really stable you can use a rough wash cloth to help the skin. This is important because, when you have a big cut you don't want to touch it, but when you put on a prosthesis that is what you will be walking on so you need to tolerate the pressures. If you consider funding it can also take a bit longer.



Does the body sometimes reject the artificial limb? Like if the person has the implants will the body not want to work with it?

A lot of people develop metal allergies. Titanium is a common one and surgical stainless steel is another one. Everyone's body is a little different. Some people can tolerate one implant and the next implant their immune system jumps in and says nu-uh. It is actually not a very common thing to get the implants. They tried it a few times and at one point they found out the implants that were attached to the bone were actually breaking down the bone in a certain percentage of people. At first the implants weren't actually left inside the body. What they would do is leave muscle loops that go through this open hole and the would put on the prosthesis and flex those muscles and it would move the prosthesis. But there were a lot of issues with infections and scar tissue.They go back to it periodically to try it out but they run into some of the same issues.


How much would an artificial limb cost and how much would insurance cover?

That is a very sticky subject. Reimbursement rates are just awful. You can get a basic arm prosthesis for as little as a few thousand dollars. You can get an above the knee prosthesis or hip disarticulation that could cost up to 100,000 dollars depending on what componentry is used. And a lot of insurance companies will bulk at prosthesis because they are so expensive. But a person with their prosthesis could get a new one every 2 - 5 years depending on their plan. Other people may only get one for their lifetime. Components break down, people's body change and one per lifetime is not reasonable. We are in the day and age where funding a prosthesis is virtually impossible.


Is there an amount of physical therapy a person has to do to get used to their new limb?

Absolutely. It depends on once again the persons health. Some people are really gungho about it and will work outside of their physical therapy sessions and will do much better than someone who just waits for their physical therapy sessions and doesn't even put their prosthesis on. They can start off even before they get fit with their prosthesis by doing their stretching exercises, the range of motion exercises. And then making sure the rest of their body is nice and strong because they are going to be hanging on to either parallel bars, a walker, or crutches. And they will need their upper body strength because they will be needing to rely on that to help get them around. They also need to make sure that other leg is strong if they have it. You need to also work on balance. There are other health issues that are looked at other than that you are just missing a leg.

Interview with Ms. Warner from the WTU, physical therapist

What kind of exercises do people have to do to stretch their limbs after surgery?

It depends on above or below the knee. You need to stretch your hip flexors and make sure the rest of the body is strong. Either way the hamstrings will be stretched. Your residual contractures if not stretched correctly. A contracture is where the muscles and tendons shorten up to do disuse so that your joint is bent and can't be straightened.


How long do you make people wear their limb in therapy?

It mostly depends on how new they are to the limb. But if they are just getting into the limb we only go 30 minutes and take it off just to make sure that they don't have any irritation of their skin.


If the person was running before their amputation, will you let them run, and how long will it take to get them back to being able to run?

Everyone is different. I normally work with older people so running is not an issue.First we have to get them walking, and once they are solid with walking we get them a new prosthesis that they can run in. There is no set time on how long it takes, because everyone is different.


How often do you see people who have the hip disarticulation, and if you do have someone who has hip disarticulation is it harder to work with them?

Not often do we see that. But first we have to reteach them how to walk because they don't have the natural knee joint. Then we have to work with getting them comfortable with walking.


Are there some people who do not want to work on getting better with their new limb?

Yes, some people might give up and only want to stay in the wheelchair. Most people don't want to mess with going and working for it. But some people want a limb but it is too expensive for them to get.

Sources

The O&P Edge, Fit and Function for the hip disarticulation patient magazine


A special thank you to Master Sergeant Bergom and Ms. Warner for the interviews