Test Sockets and Gel Inserts and Bulldog Locks (Oh, my!)

test sockets gel inserts gel sleeves bulldog locks

Above-Knee (AK) Prostheses¬†and Below-Knee Prostheses have come a long way from the straight, locked prosthetic limb to today’s modern devices that mimic the natural movement of a human leg. This is thanks to three key parts – the test socket, the gel insert and something called a Bulldog lock.

above knee prosthetic acrylic outer shell poly liner orion3 micro processor computer knee charger

We delivered this final version of an Above Knee Prosthetic, Acrylic Outer Shell with Poly Liner Orion3 Micro-Processor Computer Knee and Charger

What are Test Sockets?

No limb is ready for its final prosthesis immediately after surgery, but the fitting process will begin as soon as the sutures heal. This allows the person to begin physical therapy and become accustomed to using a prosthesis long before the limb has healed completely, a process that can take up to six months. Each day, the residual limb will shrink in size as the swelling goes down, but a new prosthesis won’t need to be created thanks, in part, to something called a test socket. These sockets are created to fit the residual limb in its swollen state. As the limb decreases in size, the patient can add additional layers of prosthetic lining materials to keep the socket from being too loose. If the residual limb shrinks so much that the test socket no longer is functional, a new test socket can be made to accommodate the shrinking limb. Eventually, the test socket will be replaced with a customized definitive socket that will accommodate the healed limb.

What are Gel Inserts (Gel Sleeves)?

alpha classic liners

An example of WillowWood Gel Liners we may use on a patient

While the residual limb is shrinking, a patient may need to wear a prosthetic sock over it to protect the new skin. However, a prosthetic sock has two limitations. First, it does not effectively connect to a prosthesis to allow for natural movement. Second, like socks that rub on your feet in ill-fitting shoes, a prosthetic sock can create blisters on new skin because the test socket will not be customized to the residual limb. Gel inserts (Gel Sleeves) were created as a way to connect the prosthesis to the residual limb without the risk of contact sores between them. Using silicone construction and gentle compression, gel inserts can be fitted with a screw at the end that can then be connected to the prosthesis using.

Bulldog Locks

bull dog lock release pin

Top View of Bull Dog Lock and Release Pin

Bulldog locks are heavy-duty locks that are affixed to the test socket to allow for secure connection to the AK prosthesis. A screw is inserted into the end of the gel insert that simply clicks into the bulldog lock. Once secured, the prosthesis will move with the residual limb the same way a knee and lower leg does. If you stand flat on the prosthesis, the knee will lock. If you shift your weight to begin walking, the knee will bend. For as secure as bulldog locks are, they are also easy to release. Simply press the button, and the lock will release the test socket from the screw at the end of the gel insert.

Together, test sockets, gel inserts, and bulldog locks make the prosthesis fitting process as comfortable and easy as possible. For more information or to discuss your prosthesis needs, call Advantage Prosthetics and Orthotics for a consultation today.

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