How does retrofitting work?

The key to retrofitting is the pattern and thickness of the interface material inside the liner, called the liner profile. Liners with the same profile will fit into the same socket. Because WillowWood offers a range of liners with the same profile, patients don’t need to switch sockets to switch liners. There are many instances in which it’s clinically appropriate to swap out one kind of Alpha Liner for another. Retrofitting can be used to manage residual limb volume changes or to tailor interface materials for lifestyle activities.

Interface Materials





Locking Liner Umbrellas

standard-umbrellaStandard Umbrella

• Transtibial liners with a uniform profile feature a standard umbrella.

• Standard umbrellas have a diameter of 2.7″ (68.6 mm) on every liner size.

accordion-umbrellaAccordion Umbrella

• Liners with progressive or symmetrical AK profiles feature an accordion umbrella.

• The size of an accordion umbrella changes with the size of a liner.

• The shape of the accordion umbrella permits it to smoothly blend with a patient’s anatomy for a comfortable fit.


Alpha Hybrid, Alpha Silcone, and Alpha SmartTemp use WillowWood’s Select Fabric.

  • One-Way stretch fabric controls pistoning without a distal matrix.
  • Allows circumferential stretch, yet maintains liner elongation within specified limits.
  • Allows for easy bending and flexing of the knee (applies to transtibial use only).
  • Available in two colors!

  • Select Gray fabric is used for Alpha Hybrid Liners.

  • Select Taupe fabric is used for Alpha Silicone Liners and Alpha SmartTemp Liners.

  • Transtibial liners feature a Select panel, which allows for a broader range of knee motion.

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