For those interested, Podiatry Today Magazine has just published an article I wrote titled Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?
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A leap of faith, and/or wishful thinking. -
Hi Kevin
Thanks for a succinct article on this as well as giving a nice historical perspective. Enjoyed it and found it valuable. -
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The recent discussion we had on lateral ankle instability is a good case. You seemed confused on whether a rearfoot varus was a cause of supination or not. Which is understandable as many are confused by the neutral position explanations of lateral instability.
The cause of why some feet will have lateral ankle instability, while other feet will have pronation related problems is easily explained with understanding the inter-relationship of the STJ axis and the location of center of pressure under the foot.
Eric -
Attached Files:
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Dr. Spooner why must the post be oblique? what shore is it? how deep was the heel cup? thank you
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Shore was 65 before it was applied according to the manufacturer- what was it when it had been applied to the orthosis?
Heel cup height on which side? I think they were about 10mm all around. -
https://www.youtube.com/watch?v=7BSetRI_UH4&feature=youtu.be
What I DID write, and what Dr. Root alluded to was that a high rear foot varus position places the patient at greater risk for inversion type sprains. GRF compensation for rear foot varus is PRONATION...however...what happens when the rear foot varus deformity is not compensated at the STJ? What is that called, Eric? Further, what happens when this patient's foot strikes the ground that is irregular and the foot is highly inverted at heel strike? -
Do you think we could also say that an externally oblique post promotes an external pronation moment whitin the stj for a duration superior than a not oblique post during walking? In other words, while the cop shifts ahead after the heel strike and rapidly moves away from a normal post, an oblique post could determine a supination moment control for more time.
And one last thing; is it wrong to use a valgus extrinsic post or intrinsic rearfoot wedge for a case like this? -
You could use an extrinsic valgus rearfoot, or like I did here, an intrinsic lateral heel skive. -
Did the foot go to the ground or did the orthotic bring the ground up to the foot (see medial arch)? Clearly in this patient the orthotic GRF, especially in the medial arch prevented the arch from collapsing to the ground. And the device also reduced the pronatory compensation (degree of calcaneal eversion) in the rearfoot. Has tissue stress replaced this traditional Root Functional Orthotic approach. No.
JeffAttached Files:
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One of the great things about Simon placing me on ignore is that I can respond to his posts with the same flippant attitude as he did mine when I came back to posting here. First, after looking at his orthotics, I can safely write that those are ugly...flat out ugly orthotics that I would be embarrassed to distribute to any patient. Second, in his pics of the orthotics, he shows that he abducted the foot distal to the MTJ....why? He never offers an explanation. Third, he condescendingly states: "Hint: they didn't "bring the ground up to the foot...". Nor should they, if the patient didn't present with a significant or contributory forefoot varus deformity. However, one can tell from the pic of the patients' feet that she has a rear foot varus deformity that is either barely compensated or uncompensated...thus, this patient is predisposed to lateral instability issues, (can't quite tell, because Simon didn't provide a rear view comparing RCSP to NCSP). Here's a more complete set of jpegs to illustrate my point. In this patient I took a rear view comparing RCSP to NCSP, and am offering the lateral WB plain film radiograph. [notice the calcaneal bisection is not accurately drawn...but that's OK...because it functions as merely a reference line]. Her main problem is lateral instability from the rear foot...not from the fore foot necessarily. In the following video, hers is the second foot shown...yes, she has a forefoot varus deformity, (which is shown with reference lines), but her lateral instability is mainly from the rear foot.
https://www.youtube.com/watch?v=O-5qHOOSaQs&feature=youtu.be -
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It really makes sense now. Thank you for Your time.
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I've been following your discussion with Simon and really can't add anything more to what Simon has already told you. The basis for designing optimum foot orthoses for patients is understanding what the abnormal forces and moments are which are causing the pathology and then use the foot orthosis to modify the reaction forces (i.e. ground reaction forces and orthosis reaction forces) acting on the plantar foot to reduce the magnitudes of these pathological forces and moments. This is the basis of Tissue Stress Theory which is reviewed in my article, Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?
The only thing I would do differently with the foot orthosis is to add a small valgus forefoot extension (e.g. 3 mm laterally under 5th metatarsal head skived down to 0 mm thickness 1st intermetatarsal space) which would then add the benefit of significantly increasing the external subtalar joint pronation moment during late midstance and propulsion. I treat quite a few tennis players (my office is next door to a large tennis club) and use forefoot extensions quite often in athletes who are involved in side-to-side sports such as tennis, basketball, etc. -
Simon:
Were this patient's peroneals tonically active during standing? Looks like a very similar foot to the one that I used in my paper on SALRE to illustrate the peroneal tendon activity in feet with laterally deviated STJ axes. -
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Less then two weeks away from my article being published on the cause of growing pains in children and the anatomic/pathologic link to RLS in adults, using Root biomechanics. Cheers!
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You still appear confused. You are talking about how compensation for rearfoot varus is pronation. And you are talking about how an inverted heel will cause supination. Now if you used the concepts of center of pressure relative to location of the STJ axis you could explain both of those phenomenon. Joints move when there is a net joint moment or torque. When a joint "compensates" it is moving in response to moments applied to the joint.
It is possible to have an inverted heel, that will have its center of pressure lateral to the STJ axis and it will pronate. If the heel were inverted far enough that the center of pressure under the heel was medial to the STJ axis you would get a supination moment from the pressure under the heel. It still may not supinate because there may be moments from other sources (peroneal muscles) so that there will be a net pronation moment about the STJ.
When a foot strikes irregular ground, it will tend to move in the direction of the moment created by ground reaction force. When the irregular ground is more medial you get supination moment, when the irregular ground contacts more laterally you get a pronation moment. Matt, I bet you intuitively understand this. However, this is a better explanation of why certain motions occur.
Eric -
A rear foot varus deformity that is not compensated remains inverted and is fully pronated. The peroneal tendon complex has no method of compensation to closed kinetic chain forces either from above or below, thus the patient is subject to supinatory injuries, ie., inversion type sprains. This is what Root discussed in Vol 2 on page 122 and 298. Hope this helps. -
"Uncompensated", "partially compensated"; "compensated" can you enlighten as to the derivation of this bull****, Kevin? -
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Here is what Root et al wrote in Normal and Abnormal Function of the Foot (page 340-341):
"Indirectly, a spastic peroneus longus muscle can also supinate the subtalar joint. A spastic peroneus longus muscle fixes the 1st ray in its most plantarflexed position, thus everting the forefoot relative to the rearfoot. The spasm also prevents supination from occurring around the longitudinal axis of the midtarsal joint. Therefore, only inversion at the subtalar joint can compensate for the everted forefoot position. Ground reaction against the 1st metatarsal head exerts a strong inversion force upon the rearfoot and easily overcomes the weak pronation force exerted by the peroneus longus muscle upon the subtalar joint. Thus, when the peroneus longus muscle becomes spastic, the entire foot supinates at the subtalar joint. This is the etiological factor that causes the pes cavus deformity associated with Charcot Marie Tooth's disease".
Jeff
Note: I edited the reference page number which was originally incorrect. -
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In a laterally deviated axis foot there tends to be, in the absence of muscle activation, higher loads on the lateral forefoot. This occurs because in order to balance the sum of force x distance medial to the axis has to equal the sum of force x distance lateral to the axis. When the axis is lateraly positioned the distance to parts of the foot that are lateral to the axis is smaller so the forces have to be higher. When you have higher forces laterally there will tend to be discomfort on the lateral metatarsal heads and the only way one can decrease force on the metarsal heads is to increase force on the toes. Thats why you would see chronic flexor activity. However, we are only seeing a snapshot and we shouldn't jump to conclusions without seeing the patient.
So, a valgus wedge that was big enough, would cause the STJ to pronate and with STJ pronation there is talar adduction. This would cause the STJ axis to become less laterallly positioned. This could allow increased pressures on the medial side of the foot and decreased pressures on the lateral side of the foot. This is how a valgus wedge could lead to reduced flexor activity.
The nice thing about tissue stress is that you don't have to use vague and poorly defined terms like "gain support".
Eric -
Perhaps you've misread or misinterpreted my post. I was not criticizing your orthosis treatment since you have done almost exactly what I would have done for this patient. I was just pointing out that the tonic peroneal activity seen in feet with laterally deviated STJ axes is predicted using SALRE theory but from what I remember of hearing from Drs. Root, Weed and other STJ neutral theorists, tonic peroneal muscle activity was not predicted using STJ neutral theory. That's all.:drinks -
Jeff -
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Jeff -
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It appears to me that your patient has an inverted rearfoot. If the forefoot is parallel to the ground, then she would appear to have an everted forefoot to rearfoot relationship.
Jeff -
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