Updated: Jul 29, 2020
Custom molded foot orthotics in layman’s terms are basically custom-made arch supports created from a replica mold of your unique foot. These are often made by a podiatrist or other skilled medical professional. They are much more involved than just standing in a material that captures the contours of your foot while standing, and molding a material to those contours (although there is a place for that type of device). The custom foot orthotics are usually molded in the position that the foot should be functioning in, not the position that it is currently functioning in. They can be made out of various materials. The two main categories are the built-up variety or the plate of material variety.
The built-up variety uses flexible materials that have no structural rigidity to span the length of the arch and support it. The support of the arch is provided by filling in the space between the arch and the supporting surface (insole of the shoe). These are often made of various foams, rubber, cork or similar semi-compressible materials. The main advantage of these materials is that they can be softer against the foot yet provide enough support to prevent excessive abnormal motion while positioning the foot in proper alignment. They are easier to modify and sometimes materials can pressure mold a bit as they are worn. Many are made with different layers of materials. Often, the softest layers are closest to the skin and the firmer layers are closest to the floor to give a combination of cushioning and support. This variety tends to be bulkier and take up more room in a shoe than the plate variety.
The second variety of orthotic material is a rigid or semi-rigid thin plate of material that has enough strength to span and support the arch of the foot. These materials do not require the space between the arch and the supporting surface (insole of the shoe) to be filled in as in the built up variety. This allows less bulk and allows greater versatility to fit in a greater variety of shoes. Just because these materials have rigidity does not mean they will be painful to wear against the foot. These were originally made out of a thin piece of hammered stainless steel. Materials have advanced significantly since. Most have some degree of flexibility that can function similar to the flexibility of the natural foot. There are many different materials that can be selected for their various properties. Also top covers of usually softer material can be applied over the plate to make the device softer against the skin when needed. Just because this type of orthotic does not generally have much shock absorbing material built into the device, you still get all the shock absorbing benefit that is built into the structure of the shoe. Just improving the mechanics of the foot with the positioning from the orthotic also improves shock absorption.
Selecting the correct materials is a very critical component to successful orthotics. The materials must be customized for the patient’s needs. There are many factors to consider such as the patient’s weight, foot size, type of activity, style of shoe, foot structure, type of correction needed, patient’s preference, etc. Durability is also a factor. Some materials eventually compress and lose their full correction, some do not. Some of the plastics in the plate variety will deform gradually (plastic creep) with time and continued wear, some will not. Materials used for orthotics also vary in weight. Some materials are very light weight such as some of the high tech carbon fiber plastic composites and some foams. Materials have advanced dramatically in the last few decades. A proper orthotic does not only require knowledge of foot and body mechanics, but also a knowledge of the various materials used to fabricate the orthotics. There are many factors to consider making the best custom molded foot orthotics for the patient’s specific needs.