3 common casting methods for foot orthotics

Custom foot orthotics are made with the sole intent of helping support and comfort your specific foot size and shape.

This makes them invaluable to helping you walk better, as well as decreasing your level of foot, knee, or lower back pain related to abnormal motion of your feet or other foot-related conditions.

How are the orthotics made to ensure that they fit your feet properly? Well, there are a few different casting options, all of which have their advantages.

Plaster slipper casting

In an article posted on OandP.com, a website devoted to orthotics and prosthetics information, Séamus Kennedy, certified pedorthist and president of Hersco Orthotic Labs, referred to the plastic slipper cast as “the gold standard of casting methods.” He said this type of cast works great for foot orthotics that are designed to improve the function of the foot (versus foot orthotics created to improve comfort).¹

Kennedy also said plaster casting is the best method to use when the foot is in the subtalar joint neutral position; however, research published in the Journal of Rehabilitation Research and Development suggested that the subtalar joint neutral position isn’t necessary. After testing 20 subjects and using digital scanning to analyze each mold, the researchers concluded “that as long as the forefoot and hindfoot are appropriately aligned, variations in the orientation of the subtalar joint would be acceptable.”²

A downside to plaster casts is that it takes a decent amount of time to obtain and you need to make sure it shows great detail, which isn’t always easy to do. Furthermore, those with foot flexibility issues will have more difficulty getting a good plastic cast.

Synthetic slipper casting socks

Another casting option is one that involves using synthetic polyester and Lycra^® casting socks. The nice thing about choosing this over plaster is that there is no mess. Plus, you can get a mold in just a couple of minutes, so it is possible to get it to the lab more quickly than plaster molds, which require at least 24 hours to properly dry.

Additionally, because the mold takes so quickly with the synthetic materials, it may be easier to use this type of casting on small children who seem to have a difficult time sitting still for any length of time. Of course, this would also be beneficial for someone who is in a great deal of foot-related pain and has a hard time keeping their foot in one position for too long.

Impression foam casting

A third casting option is impression foam, and this method is used roughly 65 percent of the time.¹ Impression foam is beneficial if you are taking an accommodative foot mold, which is created to help relieve pain in a certain area of the foot.

Just like with synthetic slipper casting socks, this option is quicker and easier to use than plaster casting, and the patient can be sitting versus having to lie down. The key to getting a good impression foam cast is to use slow, controlled movements and to avoid taking the impression on tile flooring, as the box that contains the impression foam may slip.

What happens after casting

Once the casts are made, they are shipped to an orthotic laboratory with the podiatrist’s prescription. According to Chicago Podiatric Surgeons, it then goes through 27 different steps over the course of approximately two weeks, finally resulting in custom foot orthotics made just for you.³

References

¹ Kennedy S. “Casting for foot orthotics—what works best?” oandp.com. http://www.oandp.com/articles/2004-08_08.asp. Published August 2004. Accessed February 2015.

² Hutchins SW, Lee CK, Lee WC, Leung AK. Is it important to position foot in subtalar joint neutral position during non-weight-bearing molding for foot orthoses? J Rehabil Res Dev. 2012:49(3);459–466.

³ American Podiatric Medical Association. “What are orthotics?” Chicago Podiatric Surgeons. http://www.chicagopodiatry.com/orthotics-description.cfm. Accessed February 2015.