Above Knee Prosthesis
The above knee amputation is also very common. However the loss of the anatomical knee does make it more difficult to walk and uses more energy than when the amputation is below the knee. Despite this, many people are able to walk very well with an above knee prosthesis These are the parts of the above knee prosthesis or artificial limb. Figure 4.6:
Socket:
Just like the below knee prosthesis, the socket is the part of the prosthesis that will be in contact with the skin. Many of the same problems with socket fit occur with an above knee prosthesis as with a below knee prosthesis. (Please see page 75) People with above the knee amputation must also learn how to adjust the socks that are worn with the leg to keep a good fit. See the section 5.4.2 on managing prosthetic socks. Unlike the below knee prosthesis, where one socket design is used for all sockets, the above knee prosthesis may have one of two socket designs that are used. The two most common types are the quadrilateral socket and the ischial ramal containment (IRC) socket. Quadrilateral Socket: Principles (Figure 4.7)
1 Total contact
2 Narrow front to back
3 Weight is borne on the ischium or buttocks bone
Things to check for a good fit:
1 The end of the stump should touch the bottom of the socket but not have too much pressure or be uncomfortable.
2 The buttocks bone should sit on the top back of the socket.
3 There should be a relief for the adductor tendon. (The muscle attachment in the upper inner leg near the groin)
4 The socket should feel snug.
5 There should be no groin pain.
Ischial Ramal Containment Socket Principles: (Figure 4.8)
1 Total Contact
2 Narrow side to side
3 The ischium or buttocks bone should be inside the socket
Things to check for a good fit:
1 The end of the stump should touch the bottom of the socket but not have too much pressure or be uncomfortable.
2 The socket should enclose the inner thigh tissue.
3 The buttocks bone sits within the back wall of the socket.
4 There should be no groin pain.
Suspension:
See Page 76 for explanation. The most common types of suspensions for the above knee prosthesis are: Silesian band (Figure 4.9): Made of cloth or leather, this belt wraps around the waist below the pelvic bone and above the hip. The belt attaches to the lateral wall of the prosthesis and buckles into the front wall of the prosthesis.
Pelvic band with external hip joint( Figure 4.10):Used when the person with an amputation has a short limb or weak hip musculature with decreased ability to control hip movement, particularly hip abduction or movement of the limb out to the side.
Suction suspension: (Figure 4.11) This suspension does not need a belt but requires the socket to be in direct close contact with the skin. Prosthetic socks are not worn with this type of socket. There is an air valve at the bottom of the socket to allow the person with amputation to push the air out of the socket. This creates negative pressure or suction inside the socket. This suspension is frequently used in younger more active persons with amputations. Putting on this type of socket requires strength, balance and coordination. The advantages of this system is the increased freedom of motion allowed while promoting the use of the remaining thigh musculature and improving comfort if correctly fitted. The person with an amputation who is using a suction suspension will need to keep a stable body weight without changes of more than 5 kg.
Knee Joint:
The knee joint is very important for both safety and mobility. For the highest degree of safety some people will choose a limb whose knee does not bend. Others may have a moving knee joint. The stability of the knee joint is related to many things. The type of knee joint, the alignment of the prosthesis and the strength of the person controlling the limb all effect how well a person can control the prosthetic knee. (Figure 4.12)
Shank:
This is the part of the limb that connects the knee and the foot. It is made of durable materials such as rust proof metal, wood, hard foam or plastic. (Figure 4.13)
Foot/Ankle:
The foot and ankle are the same for either a below the knee or above the knee prosthesis.
Cosmetic Cover:
Once the prosthesis is made it is covered with a soft material that is shaped to match the other limb. This is called the cosmetic cover. It has no functional purpose except to make the limb look more like a real limb. Some people may choose not to have the cover applied.