Knit-Rite Ultra Low Friction Sheath™ (ULFS)
The Ultra Low Friction Sheath, or ULFS, is a concept in sheaths designed to address problems and improve function for amputees where the coefficient of friction presents a problem in donning, for sockets or prosthetic shrinkers, and the socket design does not incorporate the use of a pull sock.
Donning problems addressed include proximal bunching of socks as plies are added, adductor rolls and proximally directed pressure on soft tissue, “hammocking" due to increased proximal tension from sock plies, and socket rotation. The ULFS sheath has been found to be especially beneficial for difficult-to-fit limbs, such as those with excess soft tissue or edema, bulbous distal ends, or other uniquely shaped limbs, and to aid in donning removable rigid dressings. The ULFS has also proven beneficial for donning shrinkers because it reduces skin shear and tension on the suture line. We recommend using a Soft Sock under the ULFS for shrinker applications. Furthermore, the ULFS may be used as a conventional sheath any time a maximum reduction in friction is desired.
Another benefit provided with the ULFS ultra-low coefficient of friction is that more socks can be applied to the residual limb before donning, thus providing increased soft tissue compression. This results in better socket stabilization, greater security, increased proprioception, and often improved suspension and reduced pistoning.
Using the Double Layer ULFS Sheath, made of two layers of a slick, thin nylon fabric, is simple. The patient must simply don the appropriate socks, then invert the ULFS sheath upon itself, keeping the outer layer about three inches longer than the inner layer. The wearer can very easily slide the limb completely into the socket, as the outer layer slides upon the inner layer, with reduced proximal displacement and bunching of adductor tissue and socks. It is important to leave
extra space in the outer layer to ensure that the product will slip upon itself.
The Single Layer ULFS Sheath is designed with locking liners in mind. Featuring a hole in the toe to accommodate locking devices, alignment of the single layer of ULFS material around the pin is not a problem. Almost as slick as the original ULFS, the single layer is the next best thing in donning friction reduction and provides many of the same benefits.
The ULFS is currently available in a 14" and 21" length, in five widths. Since the material is extremely thin, but does not stretch, excess material and wrinkling is imperceptible to the wearer and has not been a problem.