What Goes Into Making Custom Orthotics?
Custom orthotics are specially-made foot devices that go into shoes to help cushion, support, and/or control abnormal motions of feet. In turn, they can improve performance, prevent injury, and relieve pain, as well as slow down the progression of foot deformities and osteoarthritis. In addition, orthotics can also help with realignment of the lower extremities, including the knees, hips, and back.
When it comes to deciding whether or not you need custom orthotics, rather than just over-the-counter (OTC) inserts, the decision should be based on several factors, including your foot type, what it being treated or what the end goal is, and how much you want to spend. Not everyone needs custom orthotics, however, they can be more effective and last longer than OTC orthotics. To learn more about the differences between OTC and custom orthotics, check out my blog “Over-the-Counter vs Custom Orthotics: Which is Right for You?”.
If the decision is to proceed with custom orthotics, it is good to know what goes into creating the orthotics, especially because they are an investment and you want them to work and last years.
FUNCTIONAL VS ACCOMMODATIVE ORTHOTICS
Before going through the process of creating foot impressions, it is important to understand the differences between the two main types of custom orthotics: functional orthotics and accommodative orthotics.
Most custom orthotics are functional orthotics. Whether worn for everyday use or for sporting activities, the goals of functional orthotics are to improve the alignment of the lower extremities, support the feet, and control abnormal biomechanics that lead to the progression of foot deformities and disorders, including flatfoot deformity, bunions, and osteoarthritis. As such, the shell is more rigid and durable and is oftentimes composed of materials like polyprophylene, graphite, or carbon composites.
Unlike functional orthotics, accommodative orthotics are usually made with softer materials, such as ethylene-vinyl acetate (EVA). Instead of trying to realign the foot, accommodative orthotics are meant to provide cushion, support, and help offload any bony prominences, mainly along the plantar sides of the feet. Accommodative orthotics are commonly used for patients with diabetes or other neuropathic disorders.
Before impressions or scans of the feet can be made, it is important to perform a thorough biomechanical exam and gait analysis. The biomechanical exam consists of evaluating the foot structure of both feet (e.g. flatfoot, pes cavus/high-arched foot), the range of motion of certain joints, the flexibility or rigidity of any deformities, and the muscle strength of certain muscle groups.
The gait analysis is important for evaluating how a person walks and how he/she possibly compensates for their foot type, certain foot deformities, or any related neuromuscular disorders that exhibit signs in the lower extremities. It is important to not only look at the feet, but to also evaluate for any discrepancy between shoulder heights, abnormal motions at the hips, and the position of the knees during gait.
These exams help the podiatrist put together the best custom orthotic prescription for the person’s feet and needs.
Foot Impressions & Scans
After performing the biomechanical exam and gait analysis, foot impressions or scans need to be taken. This can be done a variety of ways, including using plaster to create molds of the feet, using a foam box to obtain impressions, or even digital scans to create 2D or 3D models.
Using plaster is still my desired way of creating molds of the feet for custom orthotics because it allows me to have the best control over the position of the feet while they are being casted, and the plaster itself produces great impressions of the feet.
The feet can be casted either with the patient in a supine or prone position, depending on the physician’s preference and/or the ability of the patient to lie prone. Next, strips of Plaster of Paris are dipped in water and then conformed to one foot at a time. As the plaster is drying, the foot is held in a certain position, pre-determined by the physician, keeping in mind the clinical and biomechanical exams, as well as based on the type of orthotic the doctor wishes to create (functional vs accommodative). Once the plaster cast is dried, it is removed from the foot and the other foot is done repeating the previous steps.
Using the patient's medical history, biomechanical exam, gait analysis, and the plaster molds, a customized orthotic prescription can be made. The molds are then sent to a lab for manufacturing. Once ready (1-3 weeks later), they are returned to the podiatrist and a follow-up appointment is made for fitting and dispensing of the orthotics to the patient.
Some physicians do not want to deal with messy plaster and, therefore, choose using casting socks, which are made with a polyurethane resin that hardens when wet. The same principles apply as with plaster molds with applying and positioning of each foot.
Plastic wrap is first placed on the lower extremity. Next, the sock is dipped in water and then applied to one foot. While it is drying, the sock is worked and massaged around the foot, making sure to get an accurate impression. At the same time, it is held in a certain position by the doctor. Once dried, the top of the sock is cut and removed from the foot. The other foot is then casted in a similar fashion.
After the sock impressions are created, they are then sent out to a lab for manufacturing and are returned to the podiatrist so they can be fitted and dispensed to the patient.
Click here to watch how STS socks are applied to create impressions of feet.
Unlike plaster and socks molds, the foam impression box simply involves stepping into a box that creates
an immediate impression of the feet. Think of it like leaving an impression in wet sand. Despite it being a very clean and quick method for creating impressions, it requires skill to create a good and accurate impression that will produce the custom orthotic one is hoping to achieve. There are many different techniques to placing and positioning the feet in the foam box, so, for physicians, it is important to take your time and not be careless with the process.
With technological advances, numerous digital foot scanners have become available. There may be a learning curve for the physician, depending on the scanner and technology used, however, it appears that these scanners will become the future, potentially saving time, money, and a mess (2). Future research will likely need to be conducted to compare the use of these scanners to the other techniques.
The prescription is a form podiatrists use to create and order the custom orthotics. Each part of the orthotic is carefully crafted based on the patient’s medical history, the clinical and biomechanical examination, as well as the foot impressions. Below is a list of some of the customizations that can be made with the custom orthotic prescription.
This is the base and foundation of the orthotic. As mentioned above, more rigid materials (e.g. polyprophylene, graphite, carbon composites) are used for functional orthotics while softer materials (e.g. EVA) are used for accommodative devices. The thickness of the shell, often based on the weight of the patient, also helps determine the flexibility/rigidity of the orthotic. Other shell modifications include choosing the width of the orthotic, heel cup depth, and the addition of shell cut-outs, grooves, and/or flanges.
Rearfoot posts are the added material on the bottom heel section of custom orthotics. The purpose of the rearfoot post is to control the amount of foot pronation or supination during gait (1). They are usually left off in dress (and other low-profile) shoes because the orthotic may not fit into the shoes with the post added.
The top cover adds cushion and comfort over the orthotic shell. Several different materials are available. For sport orthotics, materials that absorb shock and have moisture-wicking and antimicrobial properties may be considered, while thinness and durability may be more important qualities for dress orthotics.
Additional Pad Options
- Metatarsal Pad: Helps offload the metatarsal heads. It is used for metatarsalgia or fat pad atrophy along the ball of the foot.
- Dancers Pad: Offloads the 1st metatarsal head. It is used for sesamoiditis and other sesamoid problems.
- Reverse Morton’s Extension: Offloads the 1st metatarsal head and hallux digit. It is used for early stages of hallux limitus.
- Morton’s Extension: A rigid extension is added under the 1st metatarsal joint and hallux to prevent the 1st metatarsal-phlangeal joint from bending in end-stage hallux limitus (aka hallux rigidus).
BREAKING THE ORTHOTICS IN
Once the custom-molded orthotics are returned from the lab, a follow-up appointment is made for the fitting and dispensing of the orthotics. Because the orthotics can have effects to the entire lower extremity, it is important to break them in SLOWLY. Recommended break-in time is about 1-2 weeks; therefore, they should only be worn for no more than one hour the first day, 2 hours the next day, 3 hours the following, and so forth, until they are comfortably worn full-time. It is recommended that you wear them in any shoe they fit. Think of them as eyeglasses, in that they only work when wearing them!
As you can see, there is quite a bit that goes into creating custom orthotics; however, it is important to take all things into consideration, including the patient's medical history, the clinical & biomechanical exams, and the gait analysis, to ensure the best custom orthotic is created. The end goal is for the orthotics to be effective and last several years.
If you are interested in custom orthotics, please contact the doctor to schedule an appointment.
1. Kirby, K.A. (1996). Troubleshooting Functional Foot Orthoses. In R. L. Valmassy, Clinical Biomechanics of the Lower Extremities(pp. 327-348), St. Louis: Mosby.
2. Williams, B., Fuller, E. (2015). Point-Counterpoint: Scanner Casting: Is It Better Than Plaster Impression Casting? PodiatryToday 28(6) 50-55. Retrieved from https://www.podiatrytoday.com/point-counterpoint-scanner-casting-it-better-plaster-impression-casting
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