Foot Types, Asymmetry between Feet: Article by Dr. McPoil

     As I am researching for a book I am writing, I came across this good paper by the prolific writer/researcher Dr. Thomas McPoil. He discusses the variations that he sees which are similar to my findings over the years. Each one of these variations from ideal (or Normal as termed by Dr Merton Root) can and do cause symptoms due to the changes in gait that they cause. The findings were: 8.6% Forefoot Varus (this seemed low), 44.8% FF Valgus, 14.7% Plantar Flexed First Ray, 98% Tibial Varum (this seems high), and 84% Subtalar Varus. One of the important points that the paper shows that only 69% of the patients were symmetrical in deformity or variation. That is the patients showed over 30% that one foot was totally different to the other. This is found routinely in our clinic and is magnified by other reasons for asymmetry like: right or left handed, old injuries, running or walking styles, the affect of shoe gear on the force of abnormal motion on each side, etc. So, as podiatrist, we have a lot of work to do at evening out these asymmetries. Rich

https://www.jospt.org/doi/10.2519/jospt.1988.9.12.406

Tissue Stress Theory by Drs McPoil and Hunt

     This is a wonderful paper from 1995 that introduced a wonderful concept of the Load Deformation Curve to foot mechanics that was the centerpiece of a new theory of taking care of overuse injuries called Tissue Stress Theory. I believe the author spent too much time ridiculing the Root Theory to try to make his point, when the Tissue Stress Theory can stand on its own. Both theories are well founded, and can be used in treating patients. I use Root Theories all the time, and I use Tissue Stress Theory all the time. To me, they are different. Today I will not talk about Root, but talk to you about the basic concepts of the Tissue Stress Theory. I would read only the later part of the paper when the Tissue Stress Theory is discussed, unless you want to go to town on Dr. Root's Normal and Abnormal Function of the Foot Theories. Rich
PS. Dr. Root was a teacher who used the word "Normal" as "Ideal" or non injury producing, and "Abnormal" as "Pathological" or possibly injury producing. This has brought confusion to the biomechanics world at first glance, but once you understand that it seems easier to grasp.

https://www.ncbi.nlm.nih.gov/pubmed/7655482

Here are the Steps to using the Tissue Stress Theory, which when it was published in 1995, was a common treatment method for overuse injuries that are still used today.

1) Identify structures stressed (by history and symptoms)
2) Application of Examination Techniques to stress the tissue (can be done by PT or Podiatrist)
3) Determination if Mechanical Overload occurred
4) Reducing Stress to the Tissue Involved (Rest, Footwear, Orthotic Devices)
5) Healing the Tissues with modalities of ice, heat, ultrasound, etc
6) Restoration of Flexibility and Strength to the area

With this model, orthotic devices used may be temporary or permanent, OTC or custom
This was a big point in the article, that orthotics can be used as a temporary treatment (not a required lifelong treatment) and I think this is very good to bring out. Some patients need the orthotics only for the Immobilization Phase of rehabilitation, some need them permanently. It is up to the doctor/therapist/patient to decide in the long run. Rich