Below Knee Prosthetics
1. Patella Tendon Bearing
The patella tendon bearing socket places weight distribution over areas of the residual limb that are tolerant to pressure. This allows the user to put weight on the patella tendon, which is right below the kneecap. The patient is then able to minimize pressure over the residual limb and other boney areas, which are most sensitive. Most below the knee amputees are able to wear a patella weight bearing prosthesis. The Patella Tendon Bearing prosthesis is held onto the patient’s residual limb using one of the following common suspension systems.
- Removable Supracondylar
- Supracondylar Suprapatellar
- Suspension Sleeve
Patella Tendon Bearing Removable Supracondylar Suspension
Removable Supracondylar Suspension, holds the prosthesis on the residual limb by attaching above the bone on the inside of the knee. The user removes the supracondylar wedge to put the prosthesis on then puts it back in once the remnant limb is in the prosthesis. The wedge locks in over the bone of the knee. Supracondylar Suprapatellar
Supracondylar Suspension keeps the prosthesis on the limb by holding on above the inside bone of the knee. A variant of the Supracondylar Suspension design is Supracondylar Suprapatellar. This socket design extends the socket above the kneecap. This particular system is commonly used in individuals with short residual limbs because high trim of the socket improves the control the patient has of the prosthesis. Patella Tendon Bearing Suspension Sleeve
A suspension sleeve is attached to the prosthesis and held in place by tension and friction of the material. The sleeve is generally rolled up on the thigh and holds the prosthesis on with suction and friction on the patient’s skin. Suspension sleeves are made of silicone, or similar gels, neoprene and elastic fabrics. 2. Silicone Suction Suspension (3S)
Silicone suction suspension employs a roll on silicone liner that creates suction on the patient’s residual limb, and then uses a pin coming out of the bottom of the liner to lock into the prosthetic socket. It can be used with a patella tendon bearing, total surface bearing, or hydrostatic socket designs. Total surface bearing sockets which load all parts of the patient’s residual limb are often used with the 3S system. Prosthetic socks must still be worn over the silicone insert to compensate for swelling and general fluid changes in the residual limb.
We at Northcliff Orthopaedic Centre makes use of Silicone Liners developed by Össur. Iceross stands for Icelandic Roll-On Silicone Socket. It was developed by Össur Kristinsson, a prosthetist and prosthetic user, as an alternative suspension system to more conventional methods. It functions as the interface between the skin and the inner socket wall to protect the residual limb and to provide greater comfort to transtibial and transfemoral amputees while wearing their prostheses. Iceross is available in a range of designs to suit different residual limb conditions as well as activity and impact levels.
3. Suction socket
A suction socket employs a roll on silicone liner that is rolled onto the patient’s residual limb, and then uses a suspension sleeve or a Seal-end liner and a valve in the end of the socket. The suction socket can be used with total surface bearing, or hydrostatic socket designs. Total surface bearing sockets, which load all parts of the patient’s residual limb are often used with below the knee suction socket system. This system creates a positive suspension, and very little movement is allowed between the prosthesis and the residual limb. Prosthetic socks must still be worn over the silicone insert to compensate for swelling and general fluid changes in the residual limb.