Does the Underlay Open affect prosthetic liner grip?
One of the first questions prosthetic users and clinicians often have about wearing a textile underneath a liner is simple: will adding another layer affect the traction between the skin and the prosthetic liner?
Liner contact plays an important role in prosthetic suspension and stability, so preserving that interface was a major consideration when we developed the Ethnocare Underlay.
Rather than placing fabric underneath the entire residual limb, the Underlay Open was intentionally designed with an open distal section.
This allows the end of the residual limb to remain in direct contact with the prosthetic liner while the textile portion of the Underlay helps manage moisture higher up the limb.
We tested the design for traction
We wanted to understand how much pulling force could be applied before the prosthetic liner began to move.
During our bench testing, the Underlay Open resisted approximately 333 N to 490 N before liner movement occurred, depending on the liner length tested.
Those numbers can be difficult to visualize.
A pulling force of 90 N, which we used as a higher-demand activity benchmark (ex: someone who is running full speed), is roughly equivalent to the weight of 9 kg or 20 lb.
The Underlay Open reached the equivalent of approximately 34 to 50 kg, or 75 to 110 lb, of pulling force before movement occurred.
That represents approximately 3.7 to 5.4 times our higher-demand benchmark.
These force equivalents are provided to make the bench-test results easier to understand and do not represent loads normally experienced during prosthetic use.
Why is the bottom of the Underlay Open actually open?
The open distal design is not simply a styling choice.
It allows an important area of the residual limb to remain directly against the liner, maintaining the skin-to-liner interface users already rely on.
At the same time, the Underlay fabric helps absorb and transport moisture upward.
The upper breathable section should extend above the prosthetic liner trim line, where moisture can reach an area exposed to air and evaporate more effectively.
This creates a simple system: direct liner contact is maintained distally while heat, sweat and humidity can be managed through the textile portion of the Underlay.
Designed as an addition to your existing prosthetic setup
The Underlay was designed to integrate into the way people already wear their prosthesis rather than requiring an entirely different system.
For users with pin-lock or seal-in suspension systems, the Underlay Open can help manage the conditions underneath the liner while maintaining distal skin-to-liner contact.
For other suspension configurations, the Underlay Closed provides an alternative design.
Choosing the correct version, size and setup is important, which is why we always recommend discussing the Underlay with your prosthetist.
The objective behind the Underlay Open is straightforward: help manage heat, sweat and humidity while preserving the liner contact that is already important to your prosthetic setup.
Learn more about the Ethnocare Underlay and find the configuration that fits your prosthetic system.
