Prosthetics

Prosthetics

Summary

Prosthetics are synthetic replacement body parts. Some are functional, and others are only for aesthetics. In many cases, prosthetics are designed for patients after a foot or leg amputation due to diabetes or a vascular disease.

Most leg prosthetics consists of the same basic components. The socket fits over the patient’s residual limb and is attached with a suspension mechanism. A rigid leg provides support and height and attaches to the flexible ankle and foot. Patients who undergo above-the-knee amputation may also have a flexible prosthetic knee as part of their device. Variations to this basic design are available to best fit the patient’s activity level and needs.

Fitting a prosthetic can be a long process that may begin before the amputation surgery. It is likely to begin with a consultation with a prosthetist, a specialist who helps fit and design prosthetics. After the amputation, patients prepare for the prosthetic through postsurgical care of their residual limb and physical therapy to build strength, balance and coordination.

When the patient is ready, the fitting process begins. First the prosthetist prepares the socket from a mold or computer scan of the patient’s residual limb. Once the socket is ready, the patient is fitted with a prototype prosthetic for testing over one or two weeks. The patient then reports any problems the device caused. The final prosthetic is built once the patient and the prosthetist are satisfied with the design.

After the prosthetic is fitted, the patient learns how to use and maintain it. Learning to walk on an artificial leg involves physical therapy and advancement through a series of mobility aides, such as a walker, crutches and a cane. The device itself requires regular maintenance.

Prosthetics provide benefits but also pose risk to users. One of the greatest benefits is regaining mobility, which helps many patients live independently. Patients may also benefit from increased confidence associated with the aesthetics of the realistic appearance of the device. However, prosthetics often require more energy during movement and can cause skin problems.

About prosthetics

Prosthetics are artificial devices used as replacement body parts. They come in many forms, including limbs or parts of limbs, breasts, hips, teeth, testicles and eyes. Depending on the type, the prosthetic may be functional, such as a flexing knee or a hearing aid, or aesthetic, such as a glass eye.

Terminology associated with prosthetics can be confusing. The word prosthetics may refer to the replacement body part or the medical science of designing, constructing, fitting and maintaining the devices. Prosthesis is another word for the device used by the patient. A prosthetist is a medical specialist who designs and fits prosthetics.

Much of the need for prosthetics is due to amputation of a limb as a result of vascular disease, injury, cancer or birth defects. About 185,000 limb amputations a year are performed in the United States, according to the Amputee Coalition of America. An estimated 1.9 million Americans are living with an amputated limb.

Lower limb amputations are more common than amputations involving the arms, hands or fingers. More than half of all lower limb amputations in the United States are related to diabetes, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Not every amputee is a good candidate for prosthetics. For example, those who are frail or have loss of vision due to diseases such as diabetic retinopathy, glaucoma or cataracts may be at risk for falls and injuries.

For patients who are candidates, there is great variety in the prosthetic legs available, but they generally consist of the same components. These include:

  • Sock or liner. Much like socks worn over the feet, the prosthetic fabric sock, gel liner or foam liner is worn over the residual limb or “stump.” This sock or liner protects the patient’s limb and provides a cushion between the limb and the prosthetic device.
  • Socket. Part of the prosthetic that fits over the residual limb and sock. It is typically made of plastic or laminated polyester. The socket may be lined with material to help reduce irritation of the limb and provide a better fit.
  • Suspension mechanism. Device or set of devices that attaches the socket to the limb. The suspension mechanism may consist of straps, suction or other means of holding the prosthetic in place.
  • Prosthetic leg. The rigid component of the device meant to replace the patient’s lost limb. It provides much of the height of the device. The leg attaches directly from the socket to the ankle in patients with below-the-knee (transtibial) amputations. For those with above-the-knee (transfemoral) amputations, a prosthetic knee is added to provide flexibility.
  • Articulating joint. Artificial joint (e.g., knee) that allows flexibility in movement such as is required for sitting, walking or kneeling. The degree of flexibility and other features of the knee will vary based on the patient’s needs. This may include a patient’s activity level, lifestyle, age and general health. Prosthetic knees may be mechanical or computerized.
  • Pylon. A tube that connects the socket at the top of the prosthetic leg to the feet. This allows rotation of the leg and helps with the absorption, storage and release of energy.
  • Terminal device. In prosthetic legs, the terminal device is the foot and ankle. Artificial feet help with balance and the flexible ankles allow walking. Much like the prosthetic knee, there are many foot and ankle prosthetics available to fit the patient’s needs. Factors to be considered are a patient’s age, weight, foot size, activity level and occupational needs. The amputation level (where the limb was severed) may also affect the type of terminal device required.

Researchers are investigating many ways of improving leg prosthetics. Innovations include artificial intelligence and sensor technology that assist in using stairs, standing, sitting and developing a natural gait.

Before the prosthetic fitting

A patient may take several steps to prepare for the fitting of a prosthetic leg. Some can be done before the foot or leg amputation. One of the most important steps is the consultation with a prosthetist, the specialist who will help fit and design the prosthetic. This consultation helps determine the best type of prosthetic to fit the patient’s activity level and lifestyle. It also begins an important relationship between the patient and the healthcare professional that may last for years.

Patients who will also be using a wheelchair part-time are advised to get expert advice in fitting this medical device as well. Many people who use wheelchairs are not correctly positioned, are poorly matched to their chair, have inadequate padding or other support, or are not taught how to shift their weight and relieve pressure spots. These issues can cause skin ulcers, orthopedic disorders and other problems.

Following the surgery, patients must allow the surgical area to heal and learn to care for their residual limb. This requires keeping the skin clean through washing at least daily with antibacterial soap. Any abnormalities that are seen during cleaning should be reported to the patient’s physician. It is also recommended that patients not pick at scabs or acne. Allowing the limb to dry completely before wrapping or other covering it is also important to prevent bacterial growth.

Wrapping the residual limb is important to limit swelling (edema) after the amputation. The swelling is a natural response as the body tries to heal, but it can prevent proper fitting of the prosthetic. A compression bandage or garment placed around the limb helps reduce the swelling. In addition, elevating the limb above the heart and physical activity can also help this process and promote healing.

Physical therapy may start within days of the amputation. This is to strengthen the other limb and the residual stump. It also improves the patient’s cardiovascular status to prepare for using the prosthetic. Initially, a physical therapist teaches the patient strengthening exercises and later the patient can perform these exercises at home. Patients may also receive occupational therapy (OT) to improve independence in daily activities. OT may involve training in use of assistive devices such as bathtub benches and reachers.

Sutures from the amputation procedure are often removed within three weeks of surgery. It may take another nine weeks for the prosthetic fitting to occur. Such a long waiting period can lead to limb weakness or joint stiffness. An immediate postoperative prosthetic (IPOP) or preparatory limb may be fitted within days of the surgery to prevent loss of muscle as well as reduce swelling.

Certain types of postsurgical care can help prepare a patient for a prosthesis. For example, mild compression may speed stump shrinkage, which is a normal part of healing after amputation. A prosthesis is usually fitted after stump shrinkage has completed to help ensure a good fit.

It is important that the patient follow the physician’s recommendations after the amputation procedure. This follow-up care may include medications, a nutritious diet, keeping appointments with the healthcare team and several types of exercise, such as strengthening, range-of-motion and endurance exercises.

Prior to a prosthetic fitting, a prosthetist obtains measurements for the socket into which the patient’s residual limb will fit. For years, this required creating a mold of the residual limb. The socket was then made to fit the mold of the patient’s limb. Recent technological advances allow for a computer to scan the residual limb and take detailed measurements. The data can then be inputted into a machine that will build a socket. Whichever method is used, the socket is likely to be tested on the patient’s limb for fit before progressing with building the prosthetic.

It may be a few weeks after an amputation before a prosthetic fitting occurs.

During the prosthetic fitting

During a fitting, patients may be asked to put on and take off the prosthesis, as well as to walk with it. Patients may also require training and practice in how to transfer their weight onto the prosthetic device (e.g., from sitting to standing to walking).

The prosthetist is likely to first build a prototype (temporary) prosthetic for the patient to test. This prototype is the basis for designing and building the final prosthetic. Because the final (definitive) prosthetic may be used for two or more years, it is recommended that patients report any issues with comfort and functionality of the device, especially if it causes pain. The final device is designed and built using the patient’s input from this testing period.

Problems with fit may occur for a variety of reasons. Prolonged sitting or improper body position during sleep can lead to contracture (shortening of muscle tissue, which inhibits movement) in the residual limb. Contracture can cause a poor fit of a prosthesis or can lead to the inability to use a prosthesis.

In addition, the socket must be designed to disburse weight load as much as possible. After an amputation, the residual limb ends up bearing a patient’s weight, when it was never intended to perform that function. Improperly designed sockets can cause continuing pain. If this is the reason for the pain, the prosthesis may need to be modified. A socket that is too tight can cause swelling and red, irritated skin in the residual limb.

The last step in fitting the prosthetic is choosing its cosmetic appearance. There are many possibilities. Patients may opt for a natural look that matches their skin tone, including realistic veins, freckles and hair. Others may choose a decorated leg that pleases their personality and individual tastes. Whatever the appearance, it is primarily aesthetic and has little to no effect on the prosthetic’s function.

After the prosthetic fitting

After a prosthetic is fitted, patients require physical therapy to learn to use the new device. This may begin with exercises to increase strength. Patients may also walk between parallel bars to develop balance using the new leg. This advances to walking with assistive devices, such as a walker, crutches or a cane.

Using a prosthetic requires patients to take care of their residual limb and their overall health. The patient will need to continue to clean the limb daily and inspect it for signs of infection and disease. Keeping the sock or liner clean is also important to help prevent infection.

In addition, many patients injure their remaining foot following the amputation of the other. For people with diabetes, even a seemingly minor condition such as a scrape or bunion can lead to a foot ulcer or other serious foot problem. Without proper medical attention, this can lead to the loss of the remaining limb. Regular skin care, foot care and complete foot examinations are essential. Regular visits to a podiatrist may also be of help.

The prosthetist is likely to recommend how to get the longest functional life out of the prosthetic. This includes conditions to avoid, such as submerging some types of artificial limbs. In addition, prosthetics requires maintenance to keep them functioning. Normal wear and tear can, over time, strain the device and may lead to failure of the prosthetic limb and possible injury of the patient. The prosthetist may recommend inspections and preventive maintenance three to four times a year. During maintenance periods, patients may use the preparatory limb they were first given to maintain their mobility.

Prosthetic limbs last for only a few years before they need to be replaced. Some prosthetists estimate that they have a two- to three-year lifespan. Reasons to replace a device may include a patient’s weight gain or change in activity level, or because the prosthetic needs a new component, has lost functionality or is no longer safe.

Patients may also benefit from joining a support group for amputees or prosthetics users. These groups provide emotional support to patients and a means of sharing knowledge of live as a prosthetic user.

Potential benefits and risks of prosthetics

A prosthetic device, such as an artificial foot or leg, may provide many benefits for a patient after the amputation of a limb. One of the greatest benefits is mobility. Though patients may not regain their full abilities from before the surgery, many are able to live largely independent lives. Technological advances in prosthetics now allow patients to perform many recreational activities, including swimming, hiking and skiing.

There are also other benefits of a prosthetic, including:

  • Reduction of “phantom” pain from the amputated limb
  • Aesthetics, which helps boost the confidence of some patients after an amputation

Though prosthetics provide several benefits, they also pose some risks. Using a prosthetic leg requires more energy than a natural limb and can cause fatigue. Patients will need more strength to perform the same tasks they did before the amputation. This may lead to frustration and depression. Another risk is that of a second amputation. In some cases, especially in patients with diabetes, an injury to the remaining limb may become infected and require another amputation.

Skin problems may also occur, such as rash or irritation due to materials the residual limb is in contact with (e.g., sock or gel liner, suspension mechanism). A poorly fitting prosthesis can also cause friction, which may also cause skin problems.

Questions for your doctor regarding prosthetics

Preparing questions in advance can help patients have more meaningful discussions with  healthcare professionals regarding their treatment. Patients may wish to ask their doctor the following questions about prosthetics:

  1. After my amputation, do you think I will be a candidate for a prosthetic?
  2. Are there any reasons I should not get a prosthetic?
  3. Can you recommend a prosthetist? Can you recommend a support group for me?
  4. What can I do to prepare for my new leg?
  5. How can I limit the risk of injuring my stump or my remaining leg?
  6. How do I wear the prosthetic?
  7. What do I need to do to care for my prosthetic?
  8. What sort of skin care do I need to perform? How often should I have a doctor inspect my skin, stump and remaining leg?
  9. How will I recognize when my prosthetic requires maintenance?
  10. What advances are being made in the field of prosthetics, and how might they apply to me?
  11. How is my prosthetic adaptable? What components can I get for swimming, golfing, skiing or other recreational activities?
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