Keys To Orthotic Modifications For Patients Who Work On Their Feet

Patients who work on their feet have specific orthotic needs that clinicians may be able to address with appropriate modifications. These expert panelists discuss modifications for those who stand in place for long time periods, those who carry loads on uneven surfaces and workers who have prolonged pressure on their feet.

Q:

What modifications do you make to orthoses for patients who must stand in place for lengthy periods during the workday?

A:

Oftentimes, Kevin Kirby, DPM, notes that individuals who have jobs that require them to stand for prolonged periods on concrete, asphalt or other types of hard, flat surfaces will tend to develop plantar calcaneal pain and/or plantar metatarsal head pain. He says these work-related injuries occur due to the constant, unremitting pressure acting on all the weightbearing soft tissue and osseous structures of the plantar foot.

The goal of foot orthoses in these patients is to reduce the areas of high plantar pressure at the plantar calcaneus and plantar metatarsal heads, according to Dr. Kirby. He emphasizes redistributing the plantar loading forces to other areas of the foot that are not symptomatic, such as the medial and lateral longitudinal arches of the foot.

For these patients, Dr. Kirby designs orthoses that do not deform excessively. He says these orthoses consist of either polypropylene in individuals over 170 pounds or Plastazote #3 in individuals under 170 pounds. Using these materials helps redistribute the plantar pressures away from the plantar heel and forefoot, according to Dr. Kirby. He orders deep heel cups of 16 mm, a congruent medial and lateral arch contour, a thicker anterior orthosis edge of 4 to 5 mm and a 3 to 6 mm neoprene or PPT (Langer)/leather topcover to help provide extra cushioning.

“These orthoses, along with activity modification such as light duty assignments, often are able to heal even the most resistant of these cases,” says Dr. Kirby.

In Seattle, Larry Huppin, DPM, treats many Boeing employees who stand on concrete all day. He has found those people who are standing in one place on hard surfaces do not usually tolerate quite as much arch height as those who spend most of their day walking or sitting.

To help improve orthotic comfort for these patients, Dr. Huppin notes one of the easiest things to do is to make the orthosis somewhat wider. He says “standard” width orthoses — that traditionally extend medially to about the midpoint of the first metatarsal shaft — often leave a small portion of the medial foot hanging over the edge of the orthosis, which can lead to edge irritation. Making the orthosis wider not only avoids this edge irritation but also spreads the forces over a larger surface area, according to Dr. Huppin. He says a “wide” orthosis should be as wide as the foot but not wider.

Another option is simply to make the orthotic devices with a lower arch and more flexibility, notes Dr. Huppin. As he says, the advantage of this is that the devices are much more likely to be comfortable when the patient is standing for long periods on hard surfaces. He notes that the disadvantage is that when the patient is active or exercising, these devices are less likely to reduce stress effectively on those tissues, and may lead to metatarsalgia, plantar fasciitis, hallux limitus and other pathologies that orthotics commonly treat.

For patients with orthoses that are too rigid when they are standing for long periods, Dr. Huppin says one can adjust the orthosis to make it more flexible. He says one just grinds the polypropylene orthosis thinner from the bottom. By thinning the polypropylene shell, he notes one will increase the flexibility of the device and decrease the orthotic reactive force acting on the foot.

As Richard Blake, DPM, explains, functional foot orthotic devices were designed for changing movement patterns. When the patient stands for prolonged times, he says the shift in focus is to primary support and shock attenuation. The typical standing orthosis has a higher arch than a walking orthosis but more flexibility in the plastic and more overall cushioning in the materials.

Karen Langone, DPM, has moved to more flexible device shells for patients whose occupations require them to be on their feet a great deal. There are several factors she considers: whether patients are standing as in retail or walking on the job; the type of surface they are working on; and the shoegear required for their profession. The shell of the device will be inversely flexible to the firmness of the shoe and the surface, according to Dr. Langone. She emphasizes that the flexibility of the foot, the amount of equinus (if any) and the weight and the age of the patient will also determine the flexibility of the device.

One of the best and most commonly prescribed options for Dr. Huppin is to simply make patients two pair of orthoses if they stand for long periods. This way, he notes they will have a pair with a lower arch and some increased flexibility when they are standing for long periods, and a pair that conforms closely to the arch of foot with more rigidity for when they are exercising and doing other activities that put more force onto their feet.

“The concept is similar to having a specialized pair of eyeglasses for computer use in addition to day-to-day glasses,” remarks Dr. Huppin.

Q:

What orthoses do you prescribe for patients who carry, push and pull loads on uneven surfaces (commonly the case for those who work in construction or landscaping)?

A:

Dr. Blake emphasizes that such working activities definitely require more stabilization. He says most of that stabilization must come from the high top boot that patients wear but one can add some of the stabilization to the orthotic device with flat posts, deeper heel cups and wider widths.

In her geographic area, Dr. Langone sees a great deal of patients in retail, the restaurant industry, landscaping and construction. For a gardener in sneakers, she will dispense a semi-flexible device with arch reinforcement if added support is necessary along with a padded topcover.

For patients who do construction and landscaping work, Dr. Kirby will always use a polypropylene orthosis to provide additional stiffness to the boot or shoe. He says this helps protect the plantar arch structures of the foot while patients climb ladders, balance on narrow beams or walk over uneven terrain. Dr. Kirby says the orthosis often has a 3 mm neoprene or PPT/leather topcover and is of sufficient thickness to resist the extra arch flattening forces that these orthoses will experience when patients are required either to carry, push or pull heavy loads. He also recommends that these patients purchase high top boots to increase ankle stability due to their walking on uneven surfaces. In addition, if patients are climbing ladders or using shovels regularly, Dr. Kirby recommends boots with steel shanks in the arches to protect their plantar arches from these activities.

Dr. Huppin will try to make these devices a little wider than average to ensure there is an orthotic surface under the entire arch of the foot. If the orthosis is narrower than the foot and patients are applying significant pressure to it when under load, the medial edge is more likely to irritate the foot, according to Dr. Huppin. In addition, he notes these patients are usually wearing work boots that easily accommodate a wider orthosis.   

Q:

How do you modify orthoses for patients with prolonged forefoot pressure from kneeling, stooping or squatting for their jobs?

A:

In such a situation, Dr. Huppin says the primary goal is simply to transfer pressure off the metatarsal heads and redistribute it proximally onto the metatarsal neck, metatarsal shafts and the medial arch. Once again, he asserts that a wide orthosis is beneficial as it will more effectively transfer pressure to the medial arch. Dr. Huppin says a device made from a minimum cast fill will conform close to the arch of the foot and better transfer pressure off the metatarsal heads, assuming one is using an orthotic lab that does overfill the medial arch.

For a mechanic working on concrete in a traditional workboot, Dr. Langone will generally use a flexible or semi-flexible polypropylene device. For this device, she adds a padded topcover and can also add PPT arch reinforcement, if desired, for extra reinforcement with cushioning.

“It is nearly impossible to eliminate all plantar pressure from the forefoot with an orthosis,” notes Dr. Kirby.

The best way to treat metatarsal head or forefoot pain due to excessive forefoot pressure, notes Dr. Kirby, is to design the foot orthosis with a thicker than normal anterior edge that ends just at the metatarsal necks. He notes the anterior edge of the orthosis often comes in the form of a fairly deep parabola that is longer at the second and third metatarsals to make certain the end of the orthosis supports each metatarsal. Dr. Kirby says one may use metatarsal pads along with a neoprene or PPT/leather topcover of 3 to 6 mm thickness to help further cushion the forefoot.

When treating abnormal forefoot pressures, Dr. Blake emphasizes the need for an orthosis that has a full-length cover to which one can add great shock absorbing material as a forefoot extension such as 1/8 inch Poron. However, at times, he notes the abnormal pressure is to only one bone or one small area, which requires offloading with accommodations and metatarsal pads, similar to how one would treat sesamoiditis with a dancer’s pad (reverse Morton’s extension).

One trick Dr. Blake often uses is to cover the orthotic device initially with full-length leather. Within a few days to a week, he notes the leather will pick up the exact spots/area to accommodate/protect.

As Dr. Huppin notes, other modifications that will transfer pressure off the metatarsal heads include:

• a non-beveled distal edge to transfer pressure off the metatarsal heads and onto the metatarsal neck;
• a Poron metatarsal bar on the distal end of the orthosis to transfer pressure off the metatarsal heads and onto the metatarsal neck and shafts;
• a Poron forefoot extension to the sulcus, providing cushioning under the metatarsal heads to decrease velocity at forefoot contact, resulting in decreased force under the metatarsal heads; and
• a positive cast inversion to further increase orthotic arch height and more effectively transfer pressure off the metatarsal heads and onto the medial arch. n

Dr. Blake is the Past President of the American Academy of Podiatric Sports Medicine. He practices in San Francisco.

Dr. Huppin is the Medical Director of ProLab Orthotics. He is in private practice in Seattle.

Dr. Kirby is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is in private practice in Sacramento, Calif.

Dr. Langone is a Fellow of the American College of Foot and Ankle Orthopedics and Medicine and the Treasurer of the American Association for Women Podiatrists. She is a Fellow and Past President of the American Academy of Podiatric Sports Medicine. She is in private practice in Southampton, NY.