Do Rearfoot posts Work?

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While at Uni I was shown how to do rearfoot (RF) posts and to measure the RCSP and the NCSP and the tibial varum and calculate how much control to put in the post i.e. 4/4 (4 degrees inversion with 4 degrees of motion) dependent of the measurement and the clinical history.

The thing that has always nagged at me is when you see people wearing these devices for any length of time the RF post tends to "bite" into the shoe. By that I mean it will make an impression which can range from a minor indent to 4mm and above at wear the medial edge of the post contacts the shoe. I have also seen it a bit into the front edge of the device as well but usually not as bad.

What does this "biting" do to the measurement and percieved control?

I believe that any control is lost as soon as it does this to the shoe. As such I do not use rearfoot posts instead I -
Correct the foot as much as possible during the casting, Pour the cast inverted and use intrinsic RF grinds. By doing this I have found no issue with orthotics "biting" the shoe which makes the patient happier and so far I have been successful. Although that is based only on the ones that have come back for reviews!

Or is it that the orthotics are poorly made and accurate devices do not do this?

Regards

 

>Do Rearfoot posts Work?

I like to think they do, but do struggle a bit with the concept. Think about how much of the stance phase can the rearfoot post work? Its probably only a small percent at the start of the stance phase. The post is still in contact with the ground, but the 'centre of force' moves forward rapidly, so can the post still work after the first few % of the stance phase has passed???

 

Hi,
I believe RF posts work (not in accurate degree-based increments) by stabilising the orthosis, and not allowing it to rock.

As a matter of interest, I mostly post FF-only, and only use RF posts to "beef-up" an orthosis, in cases of pes planus (in conjunction with a deep heelcup/high medial flange), or post-tib dysfunction for example.

You may find this interesting:
Cornwall M W, McPoil T G. Effect of Rearfoot Posts in Reducing Forefoot Forces.
JAPMA. Vol 82. 7. (1992).


Regards,
davidh

 

We (Joanne Paton and I) have a paper accepted for publication in JAPMA in which we experimented with various designs of rearfoot posts. From this paper:

Weed et al (1979) believed that extrinsic rearfoot posts added
to orthotic shells improved control of foot position and
provided greater resistance to motion. However, investigations
into the effects of both external forefoot and rearfoot posts
have been inconclusive. The aim of this study was to examine
the effect of rearfoot post design on the lateral to medial
position and velocity of the centre of pressure path. The
study was a single-subject design. Four identical pairs of
polypropylene shells were constructed; three of
the pairs had a rearfoot post of specified design added. The
fourth pair, the control, was left without the post. F-scan
CoManlysis softwear was used to record measures of centre of
pressure velocity and displacement. The stance period data was
broken down into four functional phases in accordance with the
Rancho Los Amigos gait analysis committee definitions (Perry
1992) and the statistically significant differences between
the experimental conditions calculated and analysed. The
addition of a rearfoot post to an orthotic shell has an
influence on centre of pressure (COP) lateral to medial
position and velocity. While the effect of the post designs
appeared to provide reasonably predictable changes in COP
position, the effect of the post on COP velocity was somewhat
variable and inconsistent. The effect of the orthotic post was
both design and phase of gait dependent. It appears that the
addition of a rearfoot post and specifically the design of the
post can be used by the clinician to alter the COP position
and velocity.

Hopefully they will get around to publishing it sometime this decade

 

I agree, this is a bit of a nonesense.

 

Simon thanks for the synopsis of the study.

Perhaps I have not worded my question correctly - Given that post appear to have some effect intially as described by your study, I question as to how effective they are once they "bite into the shoe innersole". As in my mind the post then drops in points unevenly which must surely effect the transfer of the COP.

David

You mention that you mostly use FF posts. What sort of devices are you doing this with? 3/4 or full length?

mark

 

Rearfoot posts have several functions for foot orthoses:

1. Stabilize the rearfoot portion of the orthosis to frontal plane moments.

2. Stabilize the longitudinal arches of the orthosis to sagittal plane bending moments (i.e. arch flattening moments)

3. Allow for a platform by which to add heel height to the orthosis and/or to compensate for limb length discrepancy.

I use rearfoot posts in about 90% of the orthoses which I make for patients. I feel they are important to gain optimum orthosis control of the foot for most applications.

Observing how the orthosis is "biting into the shoe" was one clinical method that both John Weed and Mert Root lectured on as a way to tell how the patient was functioning on a foot orthosis. They taught that a greater medial indentation in the shoe sole from the anterior edge and rearfoot post of the orthosis indicated that the orthosis was resisting pronation of the foot. If there was greater lateral indentation in the shoe sole from the anterior edge and rearfoot post, this indicated that the orthosis was resisting supination of the foot. These little pearls from Root and Weed probably have some good mechanical basis in fact.

By the way, the amount "rearfoot post bite" is dependent also on the types of shoe sole and innersole/sockliner the orthosis is resting on. A hard rearfoot post won't hardly cause any depth of bite if it is resting on a shoe with a high durometer insole and sole.

 

Kevin

Do you think that when biting occurs that that results in a rocking of the device i.e. it deviates in pitch,control and position in the shoe?

If so how can we then say that the control is the same as the external support (not the orthotic/rearfoot post) surface has changed/deformed (shoe sole/innersole/sockliner)?

mark

 

Mostly 3/4 length.

 

Of course, if the orthosis has, for example, everted in the shoe due to an increased indentation in the medial edge of the rearfoot post and anterior edge into the sockliner/insole/sole of the shoe, then some degree of pronation control has been lost. However, if you were to then remove the rearfoot post from the same orthosis, you then wouldn't see the indentation in the rearfoot part of the insole.

Remember, just because you have not observed evidence that something has happened does not mean that it has not happened. Removing the rearfoot post would then cause the foot to get even less pronation control from the orthosis since the rearfoot portion of the orthosis would be everting more and the longitudinal arch of the orthosis would be flattening more without the rearfoot post.

In other words, the appropriate solution for indentations in shoe insoles from rearfoot posts is not to remove the rearfoot post. The appropriate solution is to make sure the orthosis is resting on a relatively nondeformable surface in the shoe or that the rearfoot post is long enough (i.e. from anterior to posterior) to decrease the medial rearfoot post compression pressure on the shoe sole/insole so that it doesn't indent as far into the sole/insole.

 

The fact it is indenting in the shoes shows how much work/force is being applied by the post. An orthotic is only as good as the surface it is placed on.

You could also argue that the post is spreading the load of the rearfoot of the orthotic over a greater area which would then allow increased resistance to indenting in the shoe.

 

Kevin

"then some degree of pronation control has been lost" - is this not a problem?

"However, if you were to then remove the rearfoot post from the same orthosis, you then wouldn't see the indentation in the rearfoot part of the insole" - is this a requirement for all orthotics to prove they are working? If there is no indent either medial or lateral then does that mean something?

"that the rearfoot post is long enough (i.e. from anterior to posterior) to decrease the medial rearfoot post compression pressure on the shoe sole/insole so that it doesn't indent as far into the sole/insole" - is there a set distance? The ones that I see have the rearfoot external post the length of the heel cup. How far would or could you go?

I see your point on the deformation of the medial long arch (MLA) without a post.

Am I getting nit picky about the lost control when the indenting/biting occurs? Or is it a matter of trade off's? i.e. rearfoot post maintains the MLA and thus increased control but loses control when it starts to bite. Complared to reduced MLA control without a rearfoot post but no loss of pronation control from biting?

 

Mark,

Dont get too hung up about it.

The points raised here are that the rearfoot post reduces pronatory force and to remove it would lessen the effect of the device and that the shoe must therefore be fairly non-deformable as Kevin says.

Leave the post on and make sure that the base of the shoe used is tough enough to take the added pressure.

job done.

 

Mark:

Answers:

It does matter if pronation control is reduced with a foot orthosis, especially if the patient's symptoms have not improved and their gait has not improved significantly. However, if the amount of pronation control given by the orthosis has reduced or eliminated their symptoms and has significantly improved their gait, then I don't worry about it, since my orthosis goals, then, have been met.

Medial and/or lateral indentation in the shoe sole means that the foot orthosis is predominantly resisting eversion moments and/or inversion moments from the patient's foot inside the shoe. It is neither good or bad, just the expected observation when treating certain foot types and pathologies. When there is no medial and/or lateral indentation, then this means the orthosis is not predominantly resisting eversion and/or inversion moments from the foot.

Reearfoot post length may be extended anteriorly to the midtarsal joint if necessary, but sometimes this length may cause sagittal plane rocking of the orthosis on the shank of the shoe. Using more rigid heel post material is absolutely necessary to ensure optimum eversion/inversion control. Longer, harder rearfoot posts will stiffen up the orthosis much more than shorter, softer rearfoot posts and will, therefore, produce better eversion/inversion control of the foot inside the shoe.

You are getting much too worried about this rearfoot post "biting". Rearfoot post "biting" is just a sign that the orthosis is working to control frontal plane motion of the foot, not a sign necessarily of orthosis malfunction.

You should be worrying more about the amount of deformation that the medial and lateral longitudinal arches of your orthosis makes when the patient functions on it. In other words, if you put your orthosis on a table top and you apply 25 pounds of vertically downward directed force onto the apex of the medial edge of the medial longitudinal arch of your orthosis with your thumb (go ahead and practice on the bathroom scales so that you can get your thumb calibrated for this test), and the medial longitudinal arch of the orthosis deforms more than 3 mm (or even worse, the whole posterior half of the orthosis everts on the table and is not stable since there is either no rearfoot post or a soft rearfoot post) then this orthosis will not be able to give great pronation control for a patient with large STJ pronation moments and large medial arch flattening moments, unless the patient weighs less than 100 pounds.

 

Dear Foot Doctor, Kevin and other posters,

I thank you both for your comments and answers to my questions. My questions which I experessed in this thread I feel have been answered.

Happy Easter

 

Hi all,

When I was teaching, and just experimenting with the medial heel skive, I made several patients devices with and without the medial heel skive. I did these with and without rearfoot posts. When you stand on an uposted device with a medial heel skive there is more flex in the device than when you stand on an uposted device without a medial heel skive. This occurs becuase the contact point between the ground and the unposted medial heel skive device is lateral the center of the device. When the anterior edge of the device is on the ground the heel cup of the medial heel skive device the medial side of the cup is higher off of the ground. This shifts the center of pressure between the orthosis and the heel cup more medial. So, the forces on the medial heel skive device from the foot is more medial and the force from the ground are more lateral. This creates a force couple that causes the device to bend more than non medial heel skive device. When you put a rearfoot post under the medial heel skive device, the center of pressure between the shoe and device is more medial and there is less flex in the device.

The clinical application of this is that you can get some increased supination moment from an unposted medial heel skive device, but not as much as a posted device. Also, if you get too much supination (peroneal fatigue, soreness) then you can decrease the supination effect by grinding off some of the plantar medial surface of the rearfoot post. Or if you do not have as much supination effect then you can rubberized cork under the medial surface to invert the heel cup further.

Cheers,

Eric Fuller

 

Regarding RF Posts Embryological development of the foot may answer this question

During my two year fellowship (guest researcher) at the Istituto Superiore di Sanita (www.iss.com) I had a chance to look at RF posts using pressure and force plate analysis and computer assisted goniometers (all proprietary, constructed by the engineers at ISS). Subsequently I used cameras in conjunction with computer assisted software. The results were quite interesting.

I believe you must first ask the question, what type of foot pathology am I dealing with, before deciding if RF posts are indicated. This question is answered in many instances (in my opinion) by first understanding the normal embryological development of the foot and then what can go wrong during gestation.

If interested, drop me an Email (rothbartsfoot@yahoo.com) and I can give you an excellent website that reviews the embryology of the foot (with animated illustrations).

regards,
Brian R

 

Brian R

Just a quick question, if you don't mind...

Are you able to give an example where rearfoot posts are not indicated?

Regards

Donna

 

When not to use RF posts

Rearfoot posts are indicated when you have a calcaneal supinatus (in embryology terms). If you are interested in viewing the embryological development of the foot, drop me an email at rothbartsfoot@yahoo.com and I will send you the URL address.

regards,
Brian R

 

Why all the secret squirrel business? Why can't you just post the URL here so everybody else can see it?

I actually asked you to explain when rearfoot posts are not indicated

Regards

Donna

 

Rearfoot Posts

In my opinion, rearfoot posts are not indicated when you do not have a calcaneal supinatus.

Below is the URL address as your requested -
http://www.rothbartsfoot.info/EmbryolWheel.html

Viewing these models (taken from Grays Anatomy and Visible Embryo) It becomes apparent, from an embryological point of view, calcaneal supinatus cannot exist without talar supinatus. Thus when supportive type orthotics are indicated, both rearfoot and forefoot posts are indicated.

Brian R

 

Donna,

I'll give you one possible answer to your question:

During sprinting.

 

Hi Simon

Thanks for that! Yeah I know I should have been more specific with my enquiry and said "apart from sprinting"...

I find it very difficult to understand how an orthosis can work effectively without a rearfoot post (either extrinsic or intrinsic)...maybe someone can enlighten me?

Regards

Donna

 

Donna:

What is a "secret squirrel"? Is that an indigenous term to your home land??

 

You don't know who Secret Squirrel is? It was a cartoon that I used to watch when I was a kid... It's actually quite disturbing because he wears a long white coat with nothing underneath...

What an agent, what a squirrel
He's got the country in a whirl.
What's his name?
Shhh...Secret Squirrel.
He's got tricks, up his sleeve,
Most bad guys, won't believe.
A bullet-proof coat, a cannon hat,
A machine gun cane with a rat tat tat tat tat.


Fights foreign spies
His disguise,
Takes him many places,
He's a squirrel of many faces,
Who's that? (Ugh!)
Who's that? (Hoot, man!)
Who's that? (Olè!)
Shhh...Secret Squirrel

Secret Squirrel

Regards

Donna

 

I think I actually do recognize that cartoon...it's just been too many years ago, I guess. My favorites here in the States during my formative years was Mighty Mouse http://www.toonopedia.com/mightym.htm and Rocky and Bullwinkle http://www.rockyandbullwinkle.com/.

 

I remember Rocky and Bullwinkle..." Hey Rocky! Watch me pull a rabbit out of a hat" "Not again? That trick never works!" They were so silly!

Back onto the subject of heel posts...I have looked at Brian's website and haven't been able to find the part that explains where heel posts are not indicated or why. Maybe I am not looking hard enough...

 

There is a lot of information on Brian's website that seems far-fetched. I think he should add that proprioceptive stimulation may allow some people to levitate...that would mesh quite nicely with the validity of the rest of the claims that he has made on his website.

However, on to the subject of rearfoot posts on orthoses: when do I not use them on my patients?

1. In patients with relatively stable feet (little pronation during midstance) that don't have symptoms caused by excessive pronation and need an orthosis that is thinner to fit more shoe styles.

2. In patients that primarily are being injured in side-to-side sports such as basketball, American football, soccer, tennis, etc. I will use generally a 5 mm polypropylene shell with a flat ground heel contact point with no rearfoot post (and a full length topcover) so that some additional flexibility is given to the device to allow the foot to have less restrictions to the ranges of inversion-eversion that are required for the sport.

3. In cobra-style dress orthoses for ladies pump style shoes and men's loafer style shoes.

Otherwise, I consider the rearfoot post an integral part of most of my patient's orthoses.

Oh, and I forgot one thing, rearfoot posts function to "reverse the anterior rotation of the innominates (hips), which in turn, positionally decompresses the intestines and colon. Waste products pass through the colon more quickly and efficiently, eliminating the pain associated with gastro-intestinal distress." What a joke!!!!

 

Thanks Kevin for the tips on rearfoot posts...makes a lot of sense However I couldn't make much sense from that website, possibly due to copious quantities of snake oil clouding the computer screen

Regards

Donna