Foot orthotics types: rigid or soft for patients?

Since there are many foot orthotics types from which to choose, chiropractic professionals need to consider which ones are best for their individual patients

The orthotic devices market is expected to grow over the next few years, and some of this anticipated growth is said to be due to an aging population that is more prone to bone disorders and injury.

However, a higher number of people seeking alternatives to surgery and improved accessibility and affordability of orthotic devices are expected to be contributing factors as well.

Since there are many foot orthotics types from which to choose, chiropractic professionals need to consider which ones are best for their individual patients. This begins with developing a clear understanding of the differences that exist among two common foot orthotics types: rigid and soft. Perhaps one of the most notable variances involves the materials with which these foot orthotics types are created from.

Foot orthotics types and materials

“A rigid orthotic is often composed of stainless steel or polypropylene or an acrylic lamination,” explains Dr. Bruce Pinker, DPM, AACFAS, FAPWCA, DABPM, a board certified podiatrist and foot surgeon at Progressive Foot Care, in White Plains, N.Y.

Conversely, a soft orthotic is typically molded from plastazote (a polyethylene foam), polyurethane foam (also known as PPT), or other types of foam, says Pinker, who has been casting for and prescribing custom-made orthotics for 20 years. 

To gain a better understanding of what each of these is, it helps to consider other common items these materials are used in. For instance, polypropylene (used in rigid orthotics) is a material that is often used when manufacturing microwaveable containers, hinges, and even car bumpers according to the website Plastics Make It Possible.

Compare that to polyethylene (a soft orthotic material), which Sciencing.com says is more commonly used to manufacture shopping bags, shampoo bottles, and other common plastic products or polyurethane (another soft orthotic material), which is typically found in padded furniture, spandex, and lycra, and it’s easier to understand the level of stability each provides.

It should also be noted that there is another type of orthotics that falls somewhere in between and that is a semi-rigid orthotic. These are “composed of leather, felt, cork, cellular rubber, polyethylene, subortholen, or tri-laminate combinations, or graphite,” explains Pinker, and are a type of orthotic that is fairly commonly used.

When considering orthotic materials, Podiatry Today stresses that it’s also important to note that “rigidity is proportional to the cube of the thickness.” Put another way, the thicker the material, the less flexibility it will provide. The length of orthotic can impact flexibility as well — which is why individuals with longer feet typically need a thicker orthotic than those with smaller feet — as can curvature of the device.

In some cases, a rigid (or semi-rigid) orthotic is more beneficial. Other times, a soft orthotic is preferred. What are some of these instances?

When a rigid orthotic is more beneficial 

Pinker calls rigid orthotics a “somewhat old-fashioned approach to managing biomechanical issues and not very popular for adults.” So, while some adults still prefer stainless steel orthotics, a semi-rigid is more commonly utilized in today’s day and age.

That being said, rigid orthotics do tend to work well when attempting to treat plantar fasciitis, Pinker says. This progressive degenerative condition impacts less than 1% of the population according to the National Center for Complementary and Integrative Health, but what is particularly troublesome is that some individuals use pain killers to ease the discomfort. With the push to reduce opioid use and abuse, this increases the priority with which to find alternative ways to treat this condition. Rigid orthotics is one such alternative and “we find that those made from polypropylene and graphite work most efficiently,” says Pinker.

Rigid orthotics can also be beneficial for children experiencing an in-toe deformity, says Pinker, further stating that “the rigid type [of orthotic] is often prescribed in the form of a gait plate.” Research confirms that gait plates offer benefits related to in-toeing. For instance, one study in the Journal of the American Podiatric Medical Association found that gait plates reduced patients’ frequency of tripping.

When a soft orthotic is preferred 

Because soft orthotic devices are more accommodative and more comfortable, Pinker says that they are often preferred when treating individuals who have been diagnosed with diabetes. PPT (polyurethane foam) is typically utilized for this purpose, providing patients with this disease the proper level of support, protection, and cushioning. 

Soft or accommodative orthotics are also preferred when managing patients post-trauma, says Pinker, especially those who are post-surgery.

The Hospital for Special Surgery adds that soft orthotics is also typically recommended if the patient has arthritis or some type of deformity “where there is a loss of protective fatty tissue on the side of the foot.” This is because soft orthotics can reduce the pressure on sore spots while, at the same time, improving balance and absorbing shock.

Conditions in which orthotics should wait

When should orthotics use be put on hold? “If a patient suffers from infection, orthotic management in the short term is not recommended,” says Pinker. “The infection must be managed immediately, and then afterwards, once the infection is resolved, orthotic management can be recommended.”

For more information on orthotics go to the Chiropractic Economics orthotics resource center at chiroeco.com/custom-orthotics.