Suspension refers to the way your prosthesis “holds” on to you, so that it does not fall off. Suspension plays a vital role because it give you a sense of security and the confidence to walk without fear of your prosthesis coming off or shifting.
There are different ways of achieving effective suspension, but your residual limb length and size has an influence on the choice we make.
Particularly long and short residual limbs have to be treated differently. The general rule is that it is easier to work with a longer residual limb.
We have systems that form a vacuum, so that the prosthesis essentially sucks onto you. This is the most commonly used method of suspension.
There is also a pin system available. This means your silicone liner has a pin at the end of the liner, which lines up with a lock inside your prosthesis when you don your prosthetic leg.
For short to very short residual limbs, we use a special elevated vacuum system and a double socket system to suspend the prosthesis. Silicone liners need to be well taken care of and must be replaced once a year.
The prosthetic knee joint is one of the most critical components of the prosthesis. Replacing the exceedingly complex human knee has been an ongoing challenge since the beginning of modern prosthetics.
A prosthetic knee has to mimic the function of a normal knee joint while providing stability and safety at a reasonable weight and cost. Developing such a knee requires familiarity with normal gait, because that is the basis for understanding an above-knee amputee’s gait.
There is a huge range of prosthetic knee joints available. The final choice will depend on your budget, age, activity levels, expectations and length of your residual limb.
At the Deist Prosthetic Centre, we are trained and have the experience to work with any type of knee joint, from your basic mechanical knee joint, pneumatic or hydraulic knee joints, all the way to your micro – processor knee joints.
If it doesn't fit correctly, you can experience pain, sores and blisters. The prosthesis will feel heavy and cumbersome. Also, your mobility may be compromised, or the prosthesis could even end up at the back of your closet.
Socket design technology has come a long way since the days of hard plastic and wooden sockets. With the emergence of contoured sockets that fit every aspect of the residual limb, amputees are more comfortable and mobile than ever before. This type of socket evenly distributes weight across the entire surface of the residual limb, eliminating pressure points. Flexible, lightweight materials enable the socket to bend and expand along with the patient's residual limb.
Fitting a socket is an art form that continuously evolves. The prosthetist's goal used to be to create a socket from softer materials; now the goal is to make the prosthesis as stable as possible, while maintaining comfort. However, even though today's materials are much lighter, it's difficult to create an inanimate prosthetic socket to comfortably contain a part of the body that is living and constantly changing.
When creating a socket, prosthetists often feel as if they're expected to stabilisesomething that seems like a stick (bone) surrounded by Jell-O (residual tissue). On top of that, they're expected to make the casing feel soft and flexible, yet stable and secure. Each socket is as unique as the person who wears it. A residual limb never keeps the same shape or consistency. To resolve this problem, prosthetists create the shape and size of the socket for the limb within a reasonable range, allowing for volume fluctuations. The wearer’s responsibility is to keep his or her weight within a range of about 2% of their body weight.
Where weight is carried within the socket can be a critical issue. With a tighter socket, weight is borne around the thigh of an above-knee amputee. If the above-knee socket is looser, more weight will be loaded on the bony structure of the pelvis area or the distal (lower) end of a below-knee limb. The goal is to balance both of these issues within a range that's comfortable for the amputee. Some amputees cannot bear weight on the distal end of their residual limb. If you're experiencing pain or redness in certain areas of your residual limb, your prosthetist can help by making slight adjustments to the socket itself or by adding socks or padding.
The use of socks and padding can be explained with this nautical analogy. Think of the residual limb as the rudder of a ship. The water can be thought of as socks. If the water level gets too low, the rudder will drag at the bottom; as water is added, the ship will rise, freeing the rudder.
Since your body continually changes, your prosthesis also requires regular adjustments to maintain alignment. It's a mechanical device, just like your car, and must be taken care of in order for it to work properly. Ideally, the alignment of prosthesis should be checked every six to twelve months. The slightest change in weight or muscle mass can change the alignment and cause problems with your residual limb. Back, hip, and knee problems can also be caused by an ill-fitting socket.
For a new amputee, the residual limb changes so rapidly in a temporary prosthesis that the alignment may require weekly updating.
One of the most important things you can do to care for your socket is to clean it thoroughly every day. Socks and liners should also be cleaned and rinsed well before donning. This can't be stressed enough. Dirty sockets, socks and liners can harbour bacteria, causing odour and skin problems, such as a rash, fungus and redness. Follow the manufacturer's directions strictly for best-practice care and cleaning instruction. If you have any questions, you should discuss the care of your prosthesis and hygiene with your prosthetist
A new amputee with a temporary prosthesis can expect that it will need to be replaced at least once before receiving a definitive prosthesis. The residual limb will shrink drastically over the first few months of wearing the prosthesis, but it may take up to two years to stabilise. Sometimes this volume loss may be handled by adding socks, but at some point the socket can become unstable, signallingthe need for a new socket. The prosthesis may require several socket changes before the limb matures.
Once the prosthetist has determined that the limb has stabilised, he or she will cast for a definitive socket. Although this is often called a permanent socket, it will need to be replaced. Just as cars wear out, so will a socket and a prosthesis. When in doubt about whether a new socket is required, contact your physician, physical therapist or prosthetist. A socket normally requires replacement when:
Amputees can surprise everyone, even their caregivers. After an amputation, an amputee may be seen as too elderly, too frail, or too seriously injured to manage walking with a prosthesis. But determination and desire can enable many people to achieve success against the odds. They don't see giving up and remaining in a wheelchair or on crutches as an option.
Learning how to wear a prosthesis and finding a socket design that works best for you can be a daunting task. Keep a list of questions for your prosthetist between appointments or call and ask. The Amputee Coalition of America is a great source for prosthetic information and can guide you in your search for answers. A support group can also provide some advice and help you realise that you're not alone.