Types of Orthotic Devices

The following is from my upcoming book "Practical Biomechanics for the Podiatrist" coming out in 2022. 

Orthotic Type:

1.     Functional 

2.     Sports 

3.     Dress

4.     Accommodative

 

     How can we truly differentiate these orthotic types? It is difficult on the surface, but let me tell you how I look at these. Every custom orthotic device I put in a shoe is functional by the fact that I am trying to have the orthotic device perform a function. However, being functional by those who manufacture orthotic devices means that function is changed by the orthotic material itself due to changes made to the custom foot cast. This is called intrinsic correction, the positive cast from the patient’s mold or foot scan, is changed to influence a new shape to the foot. Only in this arena, 3-4 degrees of forefoot varus means a lot to the manufacturing of the orthotic device, or a plantar flexed first metatarsal is treated differently than a metatarsus primus elevatus. Functional orthotic devices grew out of the necessity to help patients so crippled that they could not walk, or at least they were having a lot of symptoms. And yes, the Inverted Orthotic Technique, Root Balanced Technique, Dynamic Support Insole System, DC Wedge, Kirby Skive, Mueller Posterior Tibial, and Bi- and Tri-Axial Devices are all functional. Any repetitive motion or standing position can be the subject of change from a functional device. Therefore, motions like cycling, running, walking, rowing, golf, elliptical, etc, are all subject to predictable changes with orthotic devices. Activities like tennis, basketball, squash, etc, would be put into the sports orthotic category for sure. Therefore, if some measured degree is important when you make an orthotic device, you are probably making a functional one. 

     Sports orthotics have some element of the patient’s foot shape, but deviate from those truly functional by adding both a full length aspect and cushion full length or only in one area (like the heel). The motions in sports are so much more varied than straight walking. Both the predictability and the unpredictability has led to designs for various individual sports like ballet, basketball, tennis, soccer, etc, with relative incredible success. The full length aspect is so crucial since many athletes spend the majority (or over half) of their time just on the balls of their feet. Sports orthotics have their origin from a totally different place than functional orthotic devices. The function that the provider is attempting to fix is less a foot problem (like the degrees of forefoot varus or valgus), and more a sports problem (like the amount of heel cushion needed for a runner). A great example would be the orthotics made for ice-skating boots or ski boots that can only have a small forefoot correction and no rearfoot posting if they are to fit into a tight fitting boot. In this individual case, the boot itself gives so much support that less can be needed from the orthotic devices themselves. However, so many sports orthotic devices are so functional, and so sophisticated, that the phrase “sports orthosis” should not imply less support or “less function” by any means.

 

     Dress orthotic devices typically are just smaller versions of functional orthoses and can be made lower in the heel cup and a narrower cut. Of course, custom foot orthotic devices are always narrowed from the medial side, as it is crucial to be in full contact with the lateral border of the foot. Normally, thinner materials like carbon graphite or fiberglass are used so that the orthotic device takes up the least room possible. It is important to already know that there are no adjustments needed, as these thinner materials can not be adjusted for high spots. They can be adjusted for length and width. I typically tell my patients that I will make the athletic pair first, and based on the response and corrections needed, decide if I can use the same cast for the dress pair. With the advent of removable inserts, bigger versions of dress orthotic devices can now be made, and sometimes even an athletic cut orthosis can be fit into a “dress” shoe. So many sports, or at least foot deformities, need a great deal of correction. These corrections are built into the mold normally that is used for all orthotics. The practitioner must decide if the same mold can be used for a dress version as the correction may need to be reduced due to the bulk created. I prefer separate molds for athletic and dress orthoses when there are major corrections in the athletic cut. Some shallow shoes can not tolerate the use of a rearfoot post in dress shoes. Men’s shoes are more adaptable in general. Some of my women patients require hybrid orthoses like “cobra style” which cup the heel and support the medial arch some. 

     Accommodative orthoses protect the foot by off weighting and cushioning. These are the two big functions of this orthotic class. Probably, the over the counter diabetic insole was the first version, but I find that some customization really makes this type of orthotic device so much more effective. I typically will both take an impression cast and even do the corrections that I want in a functional device. The material that I make the orthotic device with will be soft like EVA, plastazote and poron. The EVA or plastazote becomes the heat moldable base that the orthotic device is made off, whereas poron or Spenco are just added layers like top covers for more cushion. Accommodative orthotic devices can be made in both athletic or dress versions, or standard orthotic length, sulcus length, or full length. The Hannaford device is one such full length accommodative orthosis that is very special to my practice. Multiple layers of plastazote, softest against the skin, are utilized to make this device. This device can be made off a corrected or uncorrected impression cast. Since there is no plastic, it can be adjusted in any way that fits the patient’s needs: thinned, narrowed, made stiffer, sweet spots added, varus or valgus wedging, metatarsal support, various top covers, and the list goes on and on. 

     

     In this book on Practical Biomechanics, it is hard to get away from foot orthoses. So, how do we all get better at prescribing this modality. I always feel that you should have a range of options when prescribing orthotic devices. It is important first to decide the type you will prescribe: functional, sports, dress, or some type of accommodative devices. When the patient sits in front of you, and you have just taken some form of image of their foot to send to a professional lab, first ask what do you need to accomplish. Here is the list of questions to help you make that decision?

1.     Do I need to change foot function by supporting a measurable degree of deformity, like 4 degrees forefoot varus or 5 mm metatarsus primus elevatus (Functional)?

2.     Do I need to change foot function or position not caused by a measurable degree of deformity, like correcting heel valgus from posterior tibial weakness or equinus forces (Functional)?

3.     Do I need to change the stresses occurring in sports, like dampening the impact force at the heel causing heel pain(Sports)?

4.     Do I need more stability in a narrow dress shoe (Dress)?

5.     Do I need to off weight or cushion a specific spot or the entire foot (Accommodative)?

The answers to these 5 simple questions should help you begin.