An Interface Material for Every Activity

You’ve probably heard of the concept of “retrofitting” in many aspects of your life – maybe retrofitting the windows in your house, or retrofitting the stereo in your car. In each example, you are replacing some of the equipment that was not originally part of the item.

Did you know you can do the same thing with Alpha® Liners? There are many instances in which it’s clinically appropriate to swap out one kind of Alpha Liner for another… as long as certain guidelines are followed.

Before we explain the details of retrofitting, let’s start with a quick refresher. Alpha Liners are available in four types of interface material – Classic, Hybrid, Silicone, and SmartTemp. Alpha Classic® Gel is a thermoplastic elastomer that adapts to the shape of the limb and offers the highest level of comfort and cushioning, while Alpha Silicone® is known for providing support and durability. A special type of silicone liner, called the Alpha SmartTemp® Liner, includes Outlast® thermal management technology to delay the onset of sweating. Alpha Hybrid® Gel is intended for those who need a balance between the comfort of Classic Gel and the durability of Silicone.

The type of material isn’t the only Alpha option; there are also choices with respect to the placement of the material inside the liner. Is the material thicker at the distal end than at the proximal end? Is there more material in certain areas of the liner to address specific anatomical concerns? We refer to this as the “profile.” The illustrations below show a cross-section of two of our most popular profiles, Uniform and Progressive. Some profiles, such Uniform, are available in different thicknesses. And, of course, each kind of liner is available in a selection of sizes.



With this background in mind, let’s get back to the topic of retrofitting. There are two types of retrofitting: Lifestyle Activity Retrofitting, and Volume Management Retrofitting.

Lifestyle Activity Retrofitting 

This type of retrofitting, which involves swapping a liner of one interface material for another,  is appropriate when an amputee participates in a variety of activities that cannot be sufficiently accommodated by a single type of liner. For example:

  • Starting out in a Alpha Hybrid Liner for a day at office, but putting on an Alpha Silicone Liner for a workout at the gym
  • Wearing an Alpha SmartTemp Liner while doing yardwork in the hot summer sun, then switching to an Alpha Hybrid Liner for relaxing afterward

This approach, which should only be considered when the shape and volume of the residual limb are stable, must involve liners that have the same profile, thickness, and size.

Another factor is whether the liner has a locking umbrella at the distal end or not. If a socket was created for use with a locking liner, the fit is not going to be the same if the patient switches to a cushion liner. Still another consideration is that WillowWood offers two different types of locking umbrellas – a standard umbrella, which has a smooth surface, and an accordion umbrella, which has ridges to allow it to conform to the shape of the distal end of the limb. A socket designed for one type of umbrella will not accommodate the other.

WillowWood has created a helpful guide to show exactly which part numbers will retrofit which each other. As long as these guidelines are followed, the amputee may reap the rewards provided by the different types of materials without the prosthetist having to make multiple sockets for multiple activities.

Stay tuned for our next blog, which will cover Volume Management Retrofitting!


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