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Hi All,
I have a query regarding the treatment of uncompensated and fully compensated rearfoot varus.

With an uncompensated rearfoot varus both the rearfoot and forefoot is inverted relative to the supporting surface. And in this situation the foot bears weight mostly on the lateral aspect of both the rear and forefoot. When treating the uncompensated type my understanding is that one should use an accomidative device so as to offload and protect the foot as much as possible. Please correct me if i am wrong.

With a fully compensated rearfoot varus the STJ will pronate to bring the forefoot/medial aspect of the foot to the ground and this pronation is unwanted/destructive?
However, if i treat this by preventing the unwanted pronation by either a rearfoot post or by a rearfoot post and forefoot varus (intrinsic or extrinsic, particularly if the 1st is plantarflexed) post won't i just be creating an uncompensated rearfoot varus????

OR HAVE I GOT IT ALL WRONG?

Any help would be much appreciated and thanks in advance.

LS

I won't jump straight in with an answer to your question, but I will quote Obi Wan Kenobi:

“Many of the truths we cling to depend greatly on our point of view”
Remember this when the answers to your questions arrive here.

__________________
Science is the antidote to the poison of enthusiasm and superstition

My location

No, you have it partially wrong. You are not differentiating between the forefoot and the rearfoot. A fully compensated forefoot varus means there is enough STJ rom to evert the forefoot until it reaches to the ground. A partially compensated forefoot varus means that these is some STJ motion to help reduce the inverted attitude of the forefoot but not enough to bring it parallel to the ground. An uncompensated forefoot varus means there is no STJ motion to help reduce the inverted attitude of the forefoot to the ground.

Rearfoot varus is an inverted neutral position of the STJ. A fully compensated rearfoot varus means the STJ has a sufficient rom to bring the calcaneus back to vertical. A partially compensated rearfoot varus means that the STJ can evert but the calcaneus remains somewhat inverted when the STJ is fully pronated. An uncompensated rearfoot varus means there is no STJ motion available and the heel is inverted to the floor with no compensatory motion.

In terms of treatment, if the rearfoot lacks a rom to bring the heel to vertical, the cast (ie orthosis) should be correct inverted. For example, consider a patient who has 10 degrees of forefoot varus and their STJ rom is 20 degrees of inverted with supination and 5 degrees inverted with full pronation. The total STJ rom is 15 degrees. When the STJ is fully pronated, the heel will be 5 degrees inverted and the forefoot will remain 15 degrees inverted to the floor (5 due to rearfoot and 10 due to ff to rf angle=15). You do not need to use an accommodative orthosis for this patient. You can use a functional orthosis but you need to correct the heel (balance the cast or extrinsically post the orthosis) to at least a five degree inverted rearfoot attitude to the floor. This is the maximally pronated position of the rearfoot but it is inverted! You might want to correct the heel more inverted than the maximally pronated position, say 8 or 10 degrees inverted. It depends on other factors not discussed here (ie ankle, etc.). This type of orthosis will restore ground reaction force on the medial forefoot and will therefore, reduce overload (pressure) on the lateral forefoot and lateral column. This foot type will typically have significant callous sub 5th, which the orthosis will help alleviate.

Respectfully,
Jeff
www.root-lab.com

Thanks for the reply, Jeff.
Everything you said makes perfect sense.

But my main query was the rearfoot varus. I should have made that clear.

Consider a foot with only a fully compensated rearfoot varus (no forefoot issues at all). Because i want to stop the excess STJ pronation i correct the STJ using an orthotic to its neutral postion.......................say its 10 degrees inverted. When we consider it like this haven't i just created an uncompensated rearfoot varus to some degree (i mean, the STJ still pronate to a certain degree because it has the ROM to do so)??

Or am i still getting it wrong?

Look forward to you reply

Thanks in advance.

If you have a fully compensated rearfoot varus, you (ie or most labs and practitioners) will probably position the heel of the cast either in its inverted, neutral position; or vertical; or perhaps some place between vertical and neutral. This really depends on the lab and the practitioner. There is no "right or wrong" position since you can make a reasonable argument for all of these positions. You can't 'create an uncompentated rearfoot varus" because this is a structural condition (deformity) of the foot. The patient either has an uncompensated rearfoot varus or they don't. So you are using improper terminology to describe it.

For example, if the tibia in a patient is normally vertical and your orthosis places the tibia in a position of varum, you have not "created a tibial varum" have you? Tibial varum is a structural condition (deformity) while an inverted tibia is a relative position of the tibia. We need to be careful to differentiate between fix or structural conditions and positional relationships of the body. So in the case of an orthosis that prevents compensatory eversion of the heel and allows it to function inverted, you are not "creating an uncompensated rearfoot varus", you are reducing compensatory pronation which allows the heel to function more inverted or less everted. It’s just a positional change of the heel. If you use the term uncompensated rearfoot varus, it implies something entirely different. This is why we need to be both consistent and accurate in use of terminology. I frequently find myself take liberties that I shouldn’t because technically, it is incorrect but often convenient.

You should remember that since the perpendicular forefoot to rearfoot relationship is represented in the positive cast of the foot, if you pour the cast inverted then you will be inverting the plane of the met heads by the same degree as you invert the rearfoot, which will create an inverted position of the forefoot relative to the floor. The only was to eliminate this, is to fill the anterior, medial arch to reduce this “varus like” correction. I have found that this is usually not necessary and we almost always keep the anatomical ff to rf angle of the cast in our orthoses.

Have I made this clear?

Respectfully,
Jeff
www.root-lab.com

It all depends on who drew the heel bisection and who determined STJ neutral position. When I was a student at the California College of Podiatric Medicine (CCPM) back in 1979-1983, home of the STJ neutral theory of podiatric biomechanics, we had two podiatric biomechanics professors that routinely drew their heel bisections about 5 degrees different from each other.

Therefore, in the same patient, one professor may say the patient had a 3 degree partially compensated rearfoot varus with a 3 degree inverted relaxed calcaneal stance position (RCSP) and a 4 degree forefoot valgus, then after we students had erased the calcaneal bisection lines and had the other biomechanics professor examine the same patient, then the patient would magically now have a fully compensated rearfoot varus with a 2 degree everted RCSP and a 1 degree forefoot varus deformity.

What is the lesson from this story?? Unless the heel bisections are drawn exactly the same on the posterior heel of the patient from one clinician to another then the amount of rearfoot varus/valgus that has been "determined" will correspondingly change as the examiner changes. And just imagine, if professors of biomechanics who work with each other on a daily basis at the same prestigious college of podiatric medicine that is known worldwide for its biomechanics excellence can't come within 3-4 degrees of each other with their heel bisections, what hope does the average podiatrist have of drawing the exact same heel bisection line as another podiatrist? Very little to none. I estimate the range of error in just heel bisections alone to be +/- 10 degrees if we were to have a group of 50 podiatrists all draw the heel bisection on one foot. Not very accurate when you consider the range of motion of the subtalar joint is only about 25 degrees normally.

You may want to read closely the article I just had published for Podiatry Today to get a closer look at some of the controversies surrounding the STJ neutral theory of foot biomechanics.

Like Simon said: "Many of the truths we cling to depend greatly on our point of view."

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
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Thanks Jeff,
You have made it very clear. Much appreciated.
Cheers,

The problem in the uncompensated, and partially compensated foot is the lateral column overload and relatively lateral location of center of pressure. (This lateral location of center of pressure will tend to place an abduction moment on the knee and possibly contribute to knee pathology.) So, the treatment should be directed at increasing forces under the medial forefoot so there will be a decrease in force under the lateral forefoot. This can be done with any kind of device as long as there is a forefoot varus wedge under the metatarsals.

I had a hard time figuring out how you would create an uncompensated rearfoot varus. After having tried to supinate STJ's in standing feet for many a year, I realized that you were making the assumption that something placed under the foot could comfortably supinate the Sub talar joint 7-10 degrees to get the STJ to neutral. It's not going to happen. Yes, it will be very difficult to get the STJ in neutral position while keeping the forefoot on the ground, but I question whether this should be the goal.

The vast majority of asymptomatic feet are a fully compensated rearfoot varus. Therefore, we could question whether or not these feet need any treatment. Why is an STJ position that is pronated from neutral pathologic? What structures are injured when this occurs? My instructors would have said that this "unlocks" the midtarsal joint. What pathology is caused by an unlocked midtarsal joint?

A different way of thinking is to use the tissue stress approach to foot biomechanics. Things (anatomical structures) break when placed under too much stress. To allow them to heal, they need to have the stress reduced. Design your orthosis to reduce stress on the structure that hurts. A lot of the time that will involve reducing pronation moments from the ground applied to the foot.

Regards,

Eric Fuller