Welcome to our All About Prosthetic Liners series where we break down the characteristics and uses of one of the most popular prosthetic components. In this article, we talk about the various prosthetic liner suspension systems and how they work. In part 2, we will discuss the different materials and characteristics of prosthetic liners, while in part 3, we will outline essential care tips.
The prosthetic liner is the most commonly used component for suspending or cushioning within a prosthesis. Often referred to as silicone socks or jelly liners, prosthetic liners are usually made from gel elastomers and silicone. They are designed to roll up and over the residual limb to shield the skin from friction-related skin injuries, as well as provide positive suspension of the prosthesis.
As of this writing, a properly fitting prosthetic liner is recognized as the most secure method for suspending a prosthetic limb. More prosthetic brands now manufacture various prosthetic liner options and styles, so there is something for everyone.
Just as there are different prosthetic liner styles, there are also various methods to attach a prosthesis. These methods are commonly referred to as prosthetic liner suspension systems.
Prosthetic liner suspension systems
There are many different ways to secure a prosthesis to your residual limb. Your prosthetist will recommend a prosthetic suspension system based on your abilities and circumstances.
A prosthetic suspension system works to deliver the following: easy on and off of a prosthesis, reliability which keeps the user from falling or tripping, and control as the user walks on their leg.
Pin-locking prosthetic liners
The pin lock is commonly prescribed for below-the-knee (BK) amputees. This is because the system is reliable and straightforward. A pin located on the bottom of the liner attaches into a lock built integrated into the socket. Securing your prosthesis is as simple as rolling on your prosthetic liner and having the pin engage with receptacle or lock within the socket. To doff or remove your leg prosthesis, you only need to press the release button.
Although the most common type of locking mechanism, the pin lock is not without issues. If you wear a lot of sock ply, 15-ply or more, engaging the lock with the pin can sometimes be difficult. For those amputees with sensitive distal (bottom) ends, a pin lock can create discomfort from mild pistoning of your prosthesis. Pistoning is the up and down motion of your residual limb within the socket.
The suction suspension system uses a one-way valve to maintain the negative pressure between the socket and the prosthetic liner. When the load on the artificial limb is lifted, the system stays in place by utilizing atmospheric pressure. This negative pressure system is dependent upon limb position is only activated during the swing phase of walking.
There are two types of suction suspension systems. The first uses prosthetic sleeves to seal the socket from the atmosphere. This system is commonly recommended for transtibial or below-knee sockets.
The second type of suction suspension utilizes membranes, which are often made of elastic material, to maintain negative pressure. The membranes are located on the prosthetic liner or inside the socket.
Elevated vacuum suspension
Elevated vacuum suspension operates more or less using the same concept as suction suspension; however, it requires an electrical or mechanical pump. Instead of relying on one-way valves, the system uses the pump to maintain lower pressure. As air is expelled from the prosthetic socket, your residual limb is pulled toward the socket walls and held there using the force of negative air pressure as vacuum effect is created. Elevated vacuum suspension uses an active pump to create a negative pressure difference that doesn't depend on limb position like suction.
The lanyard suspension system utilizes a cord, which is attached to the bottom of the prosthetic liner and is fed through a hole in the side or bottom of the socket and attached to the outer socket. To don your prosthesis, pull your residual limb into the socket and secure the lanyard.
This system is often recommended to amputees with very bulbous residual limbs or who have a lot of loose skin. A lanyard system also solves any issues of hypersensitivity along the bottom of a residual limb from discomfort related to pistoning and use of a pin lock system.Which suspension system are you employing right now? Share your thoughts with us by leaving a comment below.