In our last post, we discussed what custom-made (or prescription) orthotics are. Here, we are going to look at how they are made and what they are made of.
Creating quality custom orthotics is a detailed and involved process. As Richard M. Olsen, DPM, states, “The manufacture of functional foot orthotics is thus a multi-step process involving detailed and intricate cast correction, orthotic fabrication and application of additional items prescribed by your podiatrist for the treatment of your specific condition.”
Let’s take a look at the process.
The First Step in Making Custom Orthotics: Casting the Foot
After your podiatrist has completed a thorough exam of your legs and feet, taken the required measurements, looked at your shoes, and asked you about your lifestyle, she will cast your feet.
As we mentioned before, it is crucial that your podiatrist take a non-weightbearing cast of your foot. The most common method of taking this cast is by using plaster. Wet plaster strips are wrapped around the foot. The hollow, “negative foot mold” is then sent off to the orthotics lab. The lab will fill in the cast and discard the shell. The resulting “positive cast” looks like your foot.
Remember, your feet should be cast:
- In a non-weightbearing manner (you need to be sitting or lying down)
- In a neutral position (your podiatrist should ask you to roll up your pants so they can see the knee in relation to the foot and set the foot accordingly)
Your podiatrist should wait with you while the plaster hardens, watching your foot position (usually 5 to 10 minutes). The plaster usually takes a full 24-hours to harden completely, so after your podiatrist removes them from your feet, she will store them in a safe place before sending them off to the lab.
Custom Orthotics Are Made in the Lab
After your podiatrist takes the proper non-weightbearing cast of your feet, she will send the negative foot mold as well as your custom prescription to an orthotics laboratory. Your prescription will include not only the materials, dimensions, and accessories to be used in the orthotic’s manufacturing but also the specifications for the correction of the cast. These measurements are taken from the in-depth exam your podiatrist conducted before casting your foot.
This is where a custom orthotic differs from a stomp-box model. Your podiatrist will specify exactly how the orthotic should be designed to correct for the biomechanical irregularities of your feet (shown in the neutral cast). A stomp-box will simply build those bio-irregularities into the orthotic itself.
Once the positive cast has been constructed, the lab constructs the orthotics through the following steps:
- Under extreme heat, your individual cast is pressed against a sheet of graphite or plastic material.
- A cover made of comfortable yet durable material is attached to the harder heel and arch structure.
Materials Used in Custom OrthoticsFor your custom orthotics to provide optimum results, they must be constructed from materials that can resist the various forces and motions you put on your feet. In this sense, the materials need to be rigid enough to control for irregular injury-producing motion while still flexible and comfortable enough to be compatible with your activities. There are two main types of materials used for the rigid foundation of your orthotic:
- Plastics – Most plastics come from the polyolefin family. Polypropylene is the most common plastic used.
- Material thickness often ranges from 1/8” to 1/4”
- Flexibility of plastics have a wide spectrum, ranging from very flexible to relatively rigid
- Graphite – The graphite family is lighter and thinner than plastics.
- Material thickness is half that of plastic (1/16” to 1/8”)
- Also has a wide range of flexibility and rigidity
Cushioning materials such as Neoprene and open- and closed-cell forms are often used to complement the harder plastics or graphite and provide added comfort. Remember, these softer materials should never form the core structure of your orthotic.
The most common materials used to cover the plastic or graphite arch-support and heel cup come from the polyethylene foam family. These are closed-cell forms best for total-contact, pressure-reducing orthotics. Individual materials include:
- Ethyl-vinyl cetates (EVAs)
Remember, Custom Orthotics Are Custom Because They Are Made for You
A good podiatrist will take your lifestyle and body type into account when choosing materials for your orthotics. According to podiatrist Simon Spooner, PhD, two important factors are the patient’s weight and activity level. “I work with professional rugby players who weight about 280 lbs and can sprint nearly as fast as Usain Bolt. Trying to provide foot orthoses that can cope with those kind of forces is a challenge. You’ve got to pick the right horse for the right course.”
Your individual foot requires individual attention. Materials that are optimal for one person could be detrimental to another.
Tread Labs or Custom Orthotics? Hard to Tell the Difference
Tread Labs medical-grade orthotics uses the same materials as prescription orthotics.
- A molded, polypropylene arch support is the foundation of our insole. This strong, rigid structure has a spring-like nature that flexes as you walk. With this foundation, our orthotics provide structure and flexibility to match the needs of your feet.
- A layer of polyurethane foam covers our polypropylene arch support for long-lasting, reliable comfort.
- Our foam covers are topped with fast-drying polyester fabric with a silver ion, anti-microbial treatment to prevent unwanted odors. This surface is durable and low-friction, preventing hot spots and blisters.