A ProLab client called me with a question regarding a patient who is feeling that his orthoses are very comfortable when he is walking on them but they are feeling hard when he stands in one place on the orthotic devices.
This is an issue I run into a lot. I practice in Seattle and treat a lot of Boeing employees who stand on concrete all day. I have found those people that are standing in one place on hard surfaces do not usually tolerate quite as much arch height as those that spend most of their day walking or sitting.
There are some easy ways to avoid this situation and to correct for it when it does occur.
To help avoid having the patient feel excessive pressure in the arch, one of the easiest things to do is to make the orthosis somewhat wider. If the patient is going to be standing in one place for long periods of time, I like to ensure that the orthosis is the full width of the patient’s foot. Standard width orthoses, which 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. This can lead to edge irritation. By making the orthosis wider, you not only avoid this edge irritation but also spread the forces over a larger surface area.
Another hint is to always let the patient know that you would rather have the orthoses a little too rigid or little too high in the arch than have it too flexible or too low. The reasoning for this is that devices than conform better to the arch of the foot and do not collapse are usually more effective at decreasing tension on the plantar fascia, reducing pressure under the ball of the foot, and decompressing the first metatarsophalangeal joint. Those three functions take care of majority of the reasons for which we make custom orthotic devices. However, when you are making a device with that conforms very closely to the arch of the foot and that is fairly rigid, there is more potential that the patient may feel the arch of the orthoses. I let my patients to know that it is very easy to make the orthoses more flexible but almost impossible to make it more rigid or higher if it is not effective enough at taking care of their symptoms. To make the orthosis more flexible and decrease pressure on the arch, all that needs to be done is to take the polypropylene orthoses up to grinder and grind it thinner from the bottom of the orthoses. By thinning the polypropylene shell, you will increase the flexibility of the device and decrease orthotic reactive force being applied to the foot.
Another option is simply to make the orthotic devices with a lower arch and more flexibility. The advantage of this is the devices are much more likely to be comfortable when the patient is standing for long periods on hard surfaces but the disadvantage is that when the patient is active or exercising the devices are less likely to be effective reducing stress on those tissues that caused metatarsalgia, plantar fasciitis, hallux limitus, and other pathologies commonly treated with orthotics.
I think one of the best options and one that I used commonly with the patients who spent lots of time standing on hard surfaces, is to simply make them two pair of orthoses. They will have a pair with the lower arch and some increased flexibility to use when they are standing for long periods. They will have a pair that confirms closely to the arch of foot and has more rigidity for those times when they are exercising and doing other activities that put more force onto their feet. The concept is similar to have a specialized pair of eyeglasses for computer use in addition to day-to-day glasses.