Custom foot orthotics are supportive devices inserted in footwear that help to control the biomechanical functioning of the foot. In turn, this can affect the functioning of the lower limbs, which can help to deal with issues besides the foot, such as ankles, knees, hips, and lower back.
Casting the Feet
Orthotics are made from casts of the feet of which there are several methods used today. Whichever process used, the goal is to capture a three-dimensional copy of the bottom surface of the feet, which is used as a mould, or digital file from which to manufacture the orthopedic appliance.
Even within different casting processes, there are different ways to cast the foot, depending on what is needed. The foot can be casted full weight bearing, where all your body weight is used, semi-weight bearing, where some downward weight is used, and non-weight bearing, where the foot is suspended from the ground during the casing process.
The plaster cast method is one of the more well-known techniques. The patient’s foot is completely suspended, and their feet are wrapped in a plaster bandage. Wax can also be used in the same way. Another well-known method is the foam box, where the foot is pressed into a piece of foam resulting in a semi-weight bearing model. There are also digital/computer-based systems that can use used. This technique can be through a scanner or by using pins that create the shape of the foot. In both methods, the three-dimensional shape is measured digitally.
The casting methods that create a two-dimensional image is not considered a custom device. They use a pressure pad or plate to determine where the pressure occurs but does not capture the shape or height of the arch.
Creating the Orthotic
In the case of plaster casting, wax or the foam box method, the filled in, physical cast is made which is used to create the arch for the custom foot orthotic. To actually create the arch, material is heated up and vacuum formed around the physical cast. Once the material has cooled, it can be shaped into what we see as the orthotic base/arch.
The digital/computer-based systems create this orthotic base/arch digitally, and are either milled out or printed digitally. In some systems, the physical cast can be created from a digital file, which is then used as a base to vacuum form the material around.
Orthotics can be made as soft, semi-rigid or rigid. After the assessment and a discussion with your Canadian Certified Pedorthist, they will determine which is best for you. Each has its advantages and disadvantages.
Full-length orthotics are designed to replace the original liner in the shoes. They are able to be thicker and softer because of the thickness, but it may not fit in tighter shoes such as dress shoes. In this case, a three-quarter or half-length orthotic is used, which can be worn on top of the liner, provided it is not affected by any internal support the shoe may already have.
Additional features can be added to improve comfort and to address any pain. Because of all the different features and materials that can be used, your friend may have a different-looking pair. Orthotics are medical appliances, and given your particular issues it is up to the professionals to decide what would be best for you, and ultimately up to your feet to decide if the correct choices were made.
In the entire process, there can be a few or many different machines used. Some of the more common machines used are grinders, band saws, an oven, vacuum press and a fume hood to remove the glue fumes.
Talk to your Canadian Certified Pedorthist if you would like more information! To find one near you, visit https://pedorthic.ca/.
Written by Jaimie McVean, Certified Canadian Pedorthist