Three Tips for Selecting Thermoplastic Material for Orthotic Fabrication
Categories:, Hand Therapy, , Physical Therapy
It might seem overwhelming to select the proper thermoplastic material when faced with a patient who needs a custom-made orthosis. You may worry about fabricating the correct orthosis for the client’s diagnosis, making sure it fits well, and is comfortable. You also need to choose the appropriate thermoplastic material –a step that can make your task of orthotic fabrication much easier! Follow these tips to help select the most comfortable and supportive materials to meet your patient’s needs.
1. Know the Terminology of Low Temperature Thermoplastic Materials (LTTPs)
Choosing the correct LTTP is easy when we understand what makes each material unique.
Here is a glossary of terms used when describing LTTPs:
- Rigidity is the strength of the material. High rigidity is necessary for large orthoses, specific diagnoses (such as high tone), and orthoses projecting large forces.
- Memory is the ability of the material to return to its original size and shape after being stretched. This is an important concept when frequent remolding of the splint will be necessary, as in serial orthotic fabrication. Memory makes the material more cost-efficient. When working with these materials, remember to let the orthosis harden before removing, otherwise it will lose its shape rapidly.
- Bonding is the ability of the material to stick to itself or to other materials. Coated materials do not bond unless the coating is removed. Non-coated materials can be very sticky. Coated materials may be easier to work with as they can be remolded and reshaped without difficulty.
- Conformability,or drapability, is the way the material conforms to the shape of the hand. Materials with high conformability work best with gentle handling as they conform easily to arches or bony prominences. Materials with low drapability require firm handling and are recommended for larger orthoses where this moldability is less important.
- Elasticity,or resistance to stretch, is the amount of resistance the material gives to being stretched when heated. High resistance means you must work slowly and steadily to stretch the material. Low resistance means you need to work more carefully to control the material.
2. Select the Appropriate Thickness for the Size of the Patient
Thickness of a LTTP must be taken into consideration. Typically, LTTPs come in four thicknesses: 1/8”, 3/32”, 1/12”, and 1/16”. Thinner materials – such as 1/16” and 1/12” – are better for smaller orthoses for the fingers and thumbs. Larger orthoses may need thicker materials, such as 1/8” or 3/32”. Thinner LTTPs soften and harden quicker than thicker materials – meaning their working time is shorter.
3. Test the LTTP Material
Test a sample piece if you are unsure of a material’s properties and characteristics. Follow this simple guide to test your LTTP material:
- Put the sample in hot water (140°F – 160°F).
- Memory – Does the sample turn transparent? If yes, the product will have memory.
- Activation Time – How much time does it takes to get fully transparent?
- Weight – Does it float? If yes, this product will form a lightweight support for your patients.
- Take the sample out of the water.
- Coating – Does it stick to itself? Does it stick to other materials?
- Elasticity – How far can it be stretched before tearing or stop stretching?
- Mold the material over your flexed MCP joints.
- Working Time – For how long does it remain moldable?
- Conformability – How well does it conform to the shape?
- Put the sample back into the hot water.
- Memory – Does it return to original shape?
Understanding the specific attributes of each LTTP will guide you in selecting the best material for the orthosis you need to fabricate.
By Debby Schwartz, OTD, OTR/L, CHT on July 6, 2016