Differences between liner interface materials
We are often asked what are appropriate applications of thermoplastic elastomer liners and silicone liners and if there are any long term effects on residual limbs from liners? So our clinicians chatted and here is what counsel they had to share.
Alpha® Liners were introduced in 1996 and have proven to be very skin-friendly for most amputees. Today the range of Alpha Liners includes several interface material options to accommodate a variety of residual limbs. These materials have different stiffnesses and react differently to loading and shear forces during walking.
Thermoplastic elastomer (TPE) liners feature a blend of thermoplastic elastomer, mineral oil, and Vitamin E which protects the skin from abrasion and offers the highest level of comfort for the amputee. Because it is a soft, moldable material that adapts to a shape over time, TPE can accommodate geometric changes such as prominent bones on an amputee’s limb shape. This property allows these liners to be pre-stretched by the prosthetist at the time of fitting to promote an even more comfortable fit. TPE also absorbs shear forces that would otherwise be transferred to an amputee’s limb during walking, making it suitable to residual limbs which have tender skin or skin grafts. An additional benefit is that the mineral oil in these liners conditions the skin. However, TPE liners may be affected by any lotions that are applied to the skin; therefore, the use of lotions on the skin of the residual limb prior to donning a TPE liner should be avoided.
In contrast, Alpha Silicone Liners are a thermoset material and are thus firmer and less elastic. Silicone liners do not readily change shape, and exhibit less flow and force-absorbing capability compared to TPE. While silicone liners certainly offer comfort, they are better suited to more robust residual limbs and the more active amputee population. Alpha Silicone Liners also include a unique blend of Vitamin E and skin conditioners, but unlike TPE, they are not usually affected by lotions that may be applied to the skin of the residual limb. Another difference is that Silicone liners are NOT moldable by the methods that apply to TPE liners.
All Alpha Liners provide comfort and protection from load forces to the amputee. TPE liners offer the highest level of comfort, while silicone liners provide a high level of comfort and durability for the more active amputee. Of course, it is up to clinicians to determine what interface materials are best for each of their patients. If you have questions about liner interface materials, you’re always welcome to contact us.