"Original Root Postulate" on the Midtarsal Joint

The bone pin studies did show motion, but it was a very small amount of motion. The question is whether it is a clinically relevant amount of motion. As Kevin said, is the assumption of no movement good enough for your research question. A lot of the times it is. I'm ok with that one.

On the other hand, subsequent research has shown that the Elftman paper, that described the axes of the cc and tn joints becoming more parallel with STJ pronation, should not be used to explain why there is a change in range of motion of the MTJ. The Elftman paper was used as evidence for MTJ "locking". That clearly was a mistake.

Mert Root deserves a lot of credit. My feet are better off because of his and others work. However, when a mistake was made, it should be pointed out. We are building on Mert's successes. Further progress will require discarding the parts where he was wrong. I believe that he said things along those lines.

Eric

 

I think you mean Zittselberger and not Elftman. It was Zitselberger who said you didn't need any ligaments for the foot to stand up. As I understand the story, they were surprised to find that when the ligaments of the cadaver foot were cut the foot collapsed, which was contrary to the Zitselberger paper.

The locking mechanism of Elftman is clearly still in Normal and Abnormal function of the foot which was published in 1977. Van Langaalan described how many subsequent people actually misquoted Elftman. Elftman was still wrong.

Eric

 

Kevin,

I think that there is a misinterpretation of Root theory here. Thermoplastic devices were made before Root. Actually before thermoplastic, we had steel. I think that you will find anyone using steel, including Whitman, found that couldn't extend such a device past the metatarsal heads. I think that if you read Eric Lee's treatise, you'll find that Mert started out using rubber butter and semi-weightbearing casting. I will have to let Mert's surrogate, his son, speak for him -- however the thing that really makes an orthotic a Root orthotic is the nonweightbearing casting technique that he developed -- i.e. the pronation of the MTJ to its EROM (Others before were doing semi-WB casts with STJ neutral). I have not found any other person before Root advocating such MTJ positioning. And the thing that separated Root from Schuster (and the East Coast from the West Coast) was this very concept that I have decided to label the Root Postulate. If Mert and Dick had spent more time talking to each other, they may have been able to boil all their differences down to this one point, and figured out a method to solve them. It took me many many hours of discussion and debate with my friend, Dave Skliar, before I was able to find out where the fork in the road occurred.

One of the things that I think Root could have done a better job is to teach the history of the thinking processes of his predecessors, and then demonstrate how and why his ideas agreed and disagreed with them. In this way, the next generation would be better informed about what constituted originality from Root and what did not. For example, when one reads Steindler, 1929, one is impressed with a general idea that is not unlike the Root idea, i.e. correct flatfeet by inverting the rearfoot and everting the forefoot. Only problem is that Steindler was doing it outside the shoe rather than inside.

While the Root postulate has served well for a majority of my practice career, yet there are times it hasn't worked, and I have done things for some people that would make Mert turn over in his urn. This, plus the fact that people like Shavelson and Glaser and Schuster disciples still get some good results tells me that we don't fully understand the MTJ nor the other intertarsal joints. Hope you understand that I believe Root was one big flagstone in the pathway to the truth about foot function, but there were many before him, and others coming behind, all who have and will leave their stones in the path.

Best wishes,
Daryl

 

Actually, according to Nester the motion between the cuboid and navicular is comparable to or even greater than that observed at the subtalar joint. I quote:

"Many clinical models of foot biomechanics combine the navicular and cuboid, but data from Lundgren et al [26] indicates that motion between these bones is comparable or greater than that at the subtalar joint (which we never ignore) (figure 4). Identifying this capability, and the fact that motion between the medial cuneiform and navicular is equal to or greater than motion at the talonavicular joint in some feet, is perhaps one of the most important findings from the recent dynamic cadaver and invasive foot kinematic studies. This is important because data demonstrate that the tarsal bones are able to make a significant contribution to the kinematics of the overall foot. Motion that was previously attributed to the midtarsal joint and rearfoot was most likely taking place between the cuneiforms, the navicular, and cuboid. These movements are invisible clinically due to overlying tissue and consequently are completely absent from most if not all clinical models of the foot."

And yes, I would recommend that everyone reads this paper: http://www.jfootankleres.com/content/2/1/18

The section I've emboldened is pretty much saying what the Blackwood article I linked to earlier was indicating. I too would recommend that people read the full paper and not just the quotes I provided, which is why I linked the website previously. Here it is again in case you missed it: http://www.amputation.research.va.gov/limb_loss_prevention/Midtarsal_Joint_Locking.asp

To reiterate what i said with regard to the Blackwood study it was:

Doesn't resolve how you assess it clinically, but actually I quite like the idea of the three orthogonal axes approach these days which Nester and Findlow proposed: http://www.ncbi.nlm.nih.gov/pubmed/16415280

Also , I think it was Huson who noted that because each of the cuneiforms have multiple articulations that a change in the available motion at any one of the cuneiforms articulations could have an impact on the available motion across many of the bones of the midfoot region. Kevin linked his chapter from Jahss previously here: http://www.podiatry-arena.com/podiatry-forum/showthread.php?p=294724 If it's not in there, it may have been in this paper: http://www.ncbi.nlm.nih.gov/pubmed/10659527 This is why I think mobilisation / manipulation of the midfoot region can be clinically efficacious.

 

If you read Normal and Abnormal Function of the Foot you will find that the authors first described the individual characteristic of each joint (axis, rom, etc.) in a “normal” foot. They then described the interrelationship and simultaneous activity of the joints of the foot throughout the stance and swing phases of gait. This painted a functional picture for podiatrists, who prior to that time, typically had little or no real interest or appreciation of dynamic function of the foot. Next, Root et al attempted to describe osseous variations and theorized how individual conditions such as ff varus, ff valgus, single ray “deformities” such as a pf 1st met, diseases and other conditions might influence function of the foot. For most students and practitioners, this proved to be a huge step forward in their appreciation of foot function and in their ability conceptualize and approach the foot clinically.

Root et al spent a great deal of time describing how stj motion would influence relative motion at the mtj, and vice versa, especially during the stance phase of gait. The two axis mtj model was useful for teaching motion relative to the cardinal body planes, especially when relating to simultaneous motion at the stj.

I criticized Kevin for modeling the mtj as a spring or leaf because a spring does not possess dynamic components such as muscles and tendons. A leaf spring is “A composite spring, used especially in automotive suspensions, consisting of several layers of flexible metallic strips joined to act as a single unit”. The bones of the foot are not multi-layered (overlapping units) like a leaf spring but rather are beams joined by tension members. So comparing the mtj to a leaf spring is just as inaccurate as using a two axis model to describe triplane motion at the mtj. Who will be un-teaching this concept in the future?

I would challenge Kevin or anyone else who cares to take a stab at it, to describe the simultaneous motion of the osseous components of both the stj and the mtj from heel strike to toe off for us, as if you were attempting to explain it to a biomechanics student or a practitioner who didn’t have prior knowledge of your theory of foot function. Although not perfect, the Root approach did give many people such as Kevin and Daryl a good foundation for understanding how the foot functioned and how symptoms and deformities might develop as a result of pathological forces. So what better description do you have for us so we can teach people "correctly"?

 

Surely the best descriptions we have come from the in-vivo bone studies and studies employing modern imaging techniques and all the scientific data and analyses which have been performed, so why not just teach them the findings of these studies? In other words, why not just teach the best available evidence? At the time, Root may have been teaching "the best available evidence" of that time, but it's no longer that time and it's time to move on.

As the article in Podiatry Now said: "Chris [Prof. Chris Nester] said 'for me, Hannah's work will put to bed the debate about the Root model: its time to move to a data-led model of foot function using the plethora of data within the literature and Hannah's experiments'".

I agree.

 

Yes, there is fluoroscopic video of elite high jumpers on takeoff. I believe it was a Belgian group. It might have been Bart Van Gheluwe or Bart would probably know who did it. There was what they described as deformation (beyond subluxation) at the mtj as the anterior aspect of the talus was weightbearing and the navicular rode up on the dorsum of the talar neck. Extremely graphic. They had still photos at max deformation that would make you cringe!

 

I don't recall fluoroscopy, but the videos are here: http://www.indiana.edu/~sportbm/pronation.html

While shoe deformation probably contributes highly to the graphic nature of these videos, I don't believe it's all about shoe deformation. On reflection, it might well account for my asymmetrical foot function- In old money I was led to believe that I had a rearfoot valgus on one foot and a rearfoot varus on the other- the valgus was on my take off foot. However, I also had a traumatic injury to this foot aged 11, which as I recall was diagnosed as a "subluxed subtalar joint"- I wonder if this injury actually made me a better high jumper? Now, there's a thought.

 

From the book: Root, Weed and Orien: Neutral position casting techniques (1971)

“Neutral position casting duplicates the joint positions assumed by a normal foot on weightbearing. Simultaneously, the non-weightbearing plantar contour of the soft tissue must be preserved in the shape of the negative cast”.

Is it just me, or are there a number of fallacies within this statement?

 

OK, Simon, cool your jets.

I haven't done a full review of the literature yet, however just a quick look indicates that the 10 deg thing wasn't just made up. Please refer to Inman's book on Human walking in which he republishes Wright et al. paper from 1964 showing the ankle rotation in gait, showing the 10 deg thing (independent of Root). I notice that Morton in his 1952 text on Human Locomotion indicates 18 deg of ankle joint dorsiflexion before the heel leaves the ground. I also notice that Lake 1952, in his text, page 106, states that ankle joint ROM during gait ranges from 80 deg to 97 deg. Then Sarrafian (no Root fan) 1983 shows ankle joint dorsiflexion maximizes at 10 deg in late stance.

As to methodology, I agree that there is considerable variation in the measurement technique. That's why over 20 years ago I started doing both active and passive measurements, however I'm becoming ever more retiscent to dx a short Achilles. I did do some crude calculations a few years ago, and found that at about 10 deg of ankle joint dorsiflexion, with the knee straight, the CoM is about over the MTPJs. It is logical that if the CoM is behind the MTPJs, then BW is pushing the metatarsals downward, i.e. an MTPJ plantarflexion moment, and that I would want to have my CoM forward of the MTPJs before heel lift is seen to occur (I will not get into the David Winter definition of heel lift, which is really a textbook, not a short forum post.) And if this is the case, distribution of body mass is critical to dorsiflexion moment around the MTJ -- the lower the CoM, the more dorsiflexion of the ankle joint you need to get the CoM far enough forward. It makes sense that if you want to carry a heavy weight, put it on the top of your head, not in a backpack. So, I agree with Jeff, the 10 deg is a guide only, and can have a very wide variation in what is normal.

Not going to disagree that there were some who had more zeal than academics in trying to accelerate better dx and tx. There has to be a balance of both. Dr. Bill Orien's addition to Root's team was the zeal that brought Root forward out of just being a lecturer. Without him, Root would never be quoted today. I try to appreciate all the good things that our predecessors did, and try to forgive them for their inadequacies.

Best wishes,
Daryl

 

It's just you. The casting position was intended to represent the osseous relationship of the "normal" foot during midstance as the stj reached neutral and when the mtj was fully pronated about "both" axes. This is an instantaneous event as foot motion continues. Root also theorized that a "normal" foot would have the same osseous relationship in resting stance. The non-weightbearing cast was used because it would better support this osseous relationship than would a weightbearing cast of the same foot with the joints in the same position. However, the non-weighbearing cast was used primarily because most feet were not considered "ideal or normal" and would undergo compensation during stance. Therefore using a non-weightbearing cast was preferred so that the foot could be positioned with the stj neutral and the mtj fully pronated and so that cast modifications could be done to support conditions such as ff varu or ff valgus. These conditions would not otherwise be reflected if a weightbearing cast were used.

 

Jeff,

I agree with you that the two axis model makes it easy to teach FF-RF interactions occuring gait. We often have to use oversimplified models to begin to understand what's happening in life. There is no question that the Root volume 2 book is invaluable to starting an understanding of foot function. I think if you look at my copy you will see that it is in bad need for a new binding and cover. The questions I listed as #6 have yet to be answered by anyone, and so I throw it out as a challenge to try to replace the currently taught model with a better one that is more accurate. I agree that leaf spring theory doesn't begin to describe what is happening in the MTJ or how to cast a patient for an orthotic. To tell you the truth, it wasn't until Ed Glaser tried to unsuccessfully make an orthotic for me that I really started thinking earnestly about why he failed and yet my Root orthotics are so wonderful. It was from these thoughts as well as my many discussions with Dave Skliar and others that I figured out that the Root Postulate is really the basis for the success of the Root orthotic. If the Root techniques were so bad, they wouldn't have survived the last 50 years. All the skives and kinetic wedges in the world would not have been as successful if they had not been built on the basic Root shell.

Best wishes,
Daryl

 

I don't think so Jeff. As you said, Root "theorised the normal foot", did he ever actually see a foot which met his criteria in real life? I don't think I have in 25 years of looking for it. So, how did he know that the 3d dimensional model of the foot captured from all the various folk he casted using the technique was the same shape as this "theoretical ideal / normal foot" he made up in his mind? Did he ever measure the osseous relationships of the foot during casting and then compare them to the osseous relationships of his theoretical, idealised, normal foot? Did he ever measure the osseous relationship of the foot in resting stance and at the midstance of dynamic gait when patients wore his orthotics? When I say osseous relationship, I mean osseous relationship not osseous plus soft tissue. Does fluoroscopy (for example) show that the foot, when wearing a Root device adopts the position it was cast in, and moreover, the idealised foot, during the midstance of the gait cycle?

The fully pronated midtarsal joint- achieved by pulling on the fourth and fifth toes. Ignoring the fact that the pull on the toes exerted during a suspension cast applies a completely different force vector in terms of magnitude, point of application and direction to that which ground reaction force during static stance would exert on the fourth and fifth metatarsal heads? Fully pronated- really?

He also seemed to assume that foot adopted the position it was cast in when standing upon the orthotic, I think Craig showed that it didn't...

Oh and when you pull on the toes to perform the suspension, it changes the "non-weightbearing plantar contour of the soft tissue [that] must be preserved in the shape of the negative cast".

 

Daryl, in all my years of teaching biomechanics, I can honestly say that it was the two axis model of the midtarsal joint that students had the greatest difficulty in comprehending. I answered your question- I said that a data led model based on current understanding should be the model which replaces the two axis model supported by Root and yourself. Your appeal to antiquity fallacy not withstanding, I build skives and wedges into orthoses which are not casted in neutral, without "the midtarsal joint fully pronated" by pulling on the fourth and fifth toes on a daily basis, and achieve clinical success too. Moreover, if Root had it wired, there would not have needed to be skives and wedges, would there? And certainly wedges existed prior to Root.

 

Simon, sorry I'm such a visual person. So I'm going to have to postpone trying to understand your techniques until we can get together and you can show me what you're doing. Not really sure what you mean by pulling on the 4th and 5th toes. The Root technique does not distract the MTPJs. Please review my lecture I did on it on Alan Sherman's site.

As to saying that you have clinical success, I can say that Dr. Scholl also has a lot of success, as does every other orthotic maker (just read their ads). I agree that I will never argue with success and never touch an orthotic that is working.

I'm sorry that I don't know what you mean by "if Root had it wired". It seems a little bit disrespectful and sarcastic. I would ask you to try to paint a picture of what the orthotic world would have been like if there had been no Mert Root. Maybe we could remake the movie, "It's a Wonderful Life" and have Jeff Root stand in as the star to see what the world would be like. Of course you seem to think that the Brits would have had it all figured out and the Yanks just came over and messed it up. Of course without Mert, you probably wouldn't have a Kevin Kirby or a Daryl Phillips, or a Jeff Root, and Langer Lab and KLM lab would not have gotten off the ground, and you certainly wouldn't have a Tom McPoil trying to question everything.

I will look forward to your treatise on the current data model. How does it explain how to build an orthotic?

Best Wishes,
Daryl

 

Neutral Position Casting Techniques (Root, Weed and Orien) page 14: “The midtarsal joint is now fully pronated by lifting the foot and everting and abducting the forefoot to its full range of motion. During this motion, the subtalar joint must be maintained in its neutral position”.

Simon, pardon my frustration, but if someone as distinguished as you in the podiatry and biomechanics community describes the clearly written Root method of casting as “The fully pronated midtarsal joint- achieved by pulling on the fourth and fifth toes. Ignoring the fact that the pull on the toes exerted during a suspension cast applies a completely different force vector in terms of magnitude, point of application and direction to that which ground reaction force during static stance would exert on the fourth and fifth metatarsal heads? Fully pronated- really?”, then I should probably just give up!

Root specifically described the technique so that the quantity and direction of force applied by the practitioner would pronate the mtj to its end rom without pronating the stj at the same time. I can’t believe how someone who supposedly has extensively studied Root theory could be so wrong when it comes understanding the basic casting technique that Root so clearly described in his casting manual. If this is how you cast the foot (pulling up on the toes), then you have clearly never made a Root type functional orthoses in your life, since the basis of the RFO is the casting technique as described by Root. I can’t begin to describe how disappointed and frustrated I was after reading your last post.

 

I guess I was partly being facetious and partly going on how Bill Orien showed me how to do it. Notwithstanding, you "pull up on the toes" to manipulate the forefoot- right? Or, do you not pull up on the toes, Jeff? I can't believe that you, someone as distinguished within the podiatric biomechanics community can believe that this mimics the ground reaction force vector exerted in static stance and "fully locks the midtarsal joint"; that the end of RoM at the midtarsal joint is achieved in this position and with this amount of force; that the position of the subtalar joint as being "neutral" as described by Root has any meaning. I can't believe many things that you believe, Jeff. So I guess we can agree to disagree. If I have never made a Root device in my life in your opinion, I'd be quite happy, since my clinical success rate has been good and personally I don't think that Root's approach to prescription and manufacture addresses the needs of all patients. In truth, I can't remember the last time I set out to make a Root orthosis. Moreover, I do not think a lasting legacy will be made by me or any other practitioner in this day and age by promoting the erroneous ideals that were perpetuated in a book written forty years ago, but each to their own. In truth, I couldn't care less what Root thought, I'd rather go where modern science takes me. It disappoints and frustrates me that in the face of all the evidence and data that you continually defend Merton Root (I understand that he was your father, but if you wish to be taken seriously today you need to move with the science). But I'm not trying to patronise you, any more than you were trying to patronise me in your last post.

 

I'm sorry that you believe my comment was disrespectful and sarcastic, Daryl. I think the orthotic world without Merton Root would be pretty much where it is today. I presume I'm allowed to form my own opinion? You seem to presuppose that there has been a lasting legacy of Merton Root- precisely what is this legacy to the orthotic world? It's not just British scientists who have added to our knowledge of foot and lower extremity biomechanics, but scientist from all over the world. I do not think the USA has particularly added any more or less. There were lots of other people working on foot orthoses, not just Merton Root, Daryl.

In terms of the data-led model, I'll again quote Nester: " variation between people in foot kinematics is high and normal. This includes variation in how specific joints move and how combinations of joints move. The foot continues to demonstrate its flexibility in enabling us to get from A to B via a large number of different kinematic solutions. Rather than continue to apply a poorly founded model of foot type whose basis is to make all feet meet criteria for the mechanical 'ideal' or 'normal' foot, we should embrace variation between feet and identify it as an opportunity to develop patient-specific clinical models of foot function. Clinicians should consider foot function in terms of the entire foot, and, given what we know about the variation between subjects, the general ranges of motion likely at specific joints, and what is observable clinically, rationalise the most likely kinematic solution for each patient".

Me? I like a tissues stress approach, with subject specific emphasis. Are you still applying a Root model, Daryl?

BTW, I didn't say I was writing a treatise on the current data model, so this "throw away comment" comes across as either an attempt at being sarcastic or an attempt to develop a straw-man fallacy on your part, Daryl.

 

Ok Simon, I went to my happy place santa and now I'm all calmed down! Sorry that I vented on you!

How much force does it take to move the mtj to its end range of pronation? Obviously if you apply enough additional force to the mtj you will, at some point, get additional pronation. But after pronating the mtj as described by Root during casting or by placing your thumb on the plantar surface of the 4th and 5th met heads as some advocate, in most feet (certainly not all) there appears to be very little additional pronation available. The fact is, the mtj is at or extremely close to its end rom in the direction of pronation. By contrast, if you supinate the mtj from this “maximally pronated” casting position, there is a tremendous range of supination available. So whether the mtj is at 95, 98 or 100 percent of its maximum range of pronation during casting is probably irrelevant. There is clearly pronation stability along the lateral column as compared to when the joint is not in this position and the shape of the resulting orthoses will act to promote lateral column stability by resisting further mtj pronation.

If you allow the foot to pronate at the stj as you pronate the mtj, the range of pronation at the mtj increases dramatically with stj pronation. Although the term ‘locked” is a poor term to describe the maximally pronated position of the mtj, this increased range of mtj pronation that occurs as the stj is further pronated helps demonstrate the relative stability of the pronated mtj that occurs when we maintain the stj in the neutral position. It is that relative stability that we are attempting to capture in the position of the negative cast and maintain with the resulting orthosis.

Using the knee for comparison, when you fully extend the knee it doesn’t take a lot of force to move it to a position of resistance. Yes, you can force a few additional degrees of hyper-extension, but the fact is you are very close to the functional end rom of the knee in the vast majority of people, as compared to the tremendous range of flexion available. A knee brace doesn’t need to support the knee in a fully extended or hyper-extended position to effectively support the knee. So why would a functional orthoses need to capture every single degree of mtj pronation in order to be effective in supporting the mtj?

When I suffered extreme hyper-extension of the distal phalanx of my index finger attempting to catch a football many years ago, I sustained a mallet finger injury resulting in a flexed distal phalanx (approx. 30 to 40 degrees flexed). My finger was placed rectus in a splint for 12 weeks. The hyper-extension of the joint exceed my “normal” rom. Clearly joints have the ability to have an increased rom when enough force is applied. But the reality is that most joints function with a pattern of motion and typical rom and it doesn’t take much force to move a relaxed joint to very close to that normal, functional end rom. Most joints don’t have powerful tendons like the Achilles tendon that require significant force to approximate their end rom.

 

There are a number of cross conversations going on in this threads its getting confusing.

I think we talking at cross-purposes. I still it as 'Root Theory' as one thing; and the varied clinical application or interpretation of that 'Root Theory' that individuals apply in clinical practice as another thing.

 

I have watched this thread with amusement, amazement (choose you own adjective). Look people, we surely all ackowledge the fine work done by Root et al, but surely there has to be a time to let go.
The last 48 hours has rather reminded me of a time in 1991 when I published a rather poor, but to the point publication in the UK journal, entitled (something like) "questioning the corner stones of modern podiatric diagnosis". At the time of publication, the pod world was divided; half wanted me put down, the other half, said; "Thank God some one has the balls to challenge this stuff". I suspect most in The US didn't see it, simply because at the time, they didn't read UK literature. Simon is right when he says, I frankly do not much care what Root says, I simply follow science (paraphrased). Please, all out there let go, yes let go; follow science, but please never forget the forefathers.

 

Agreed. We should also be cogniscent that there may be many forefathers, with many different points of view who while being held in esteem in their own country, may be relatively unheard of outside of it. My mate Dave is world famous in Plymouth. Theodore Coates is probably a name few podiatrists in the USA recognize; Gordon Rose is another; what about Leslie Smart?

 

I had lunch with Theadore Coates )or was it his brother?) the guy that worked for unilever, got the word "orthodigita" into the Oxford dictionary. He was ok, I was 18 then, am 58 now...........

 

Yep, times change and things move forward. I've attached a few slides from a lecture I gave on the evolution of foot orthoses therapy in Belgium last year.

 

For those that might be interested to see what us Brits were up to in terms of podiatric biomechanics during the late 1950 to early 60's, here's a couple of papers from G.K. Rose.

Another favourite of mine were the series of papers published in the chiropodist by Arthur Swallow (?) Alas I no longer have copies of these, but as I recall he was pretty much describing a tissue stress approach.

 

The leaf spring model is only useful for describing that the midtarsal joint and midfoot joints do not lock, but rather continuously deform during loading situations to offer a "shock-absorbing" effect within the longitudinal arch of the foot for weightbearing activities....something that a midtarsal joint that "locked" with a few pounds of loading force could never do.

Benno Nigg wrote the following about modeling in one of his books:

Therefore, when I present that the longitudinal arch of the foot acts like a leaf spring under loading conditions, it should be understood that I am attempting to model a certain aspect of mechanical behavior of the foot but that, of course, the foot is not a leaf spring that is used in vehicular suspensions.

The purpose of describing such a model is to make podiatrists and other clinicians realize that their idea that the midtarsal and midfoot joints "lock" in place with 10 pounds of dorsiflexion loading force is erroneous, and that the position of the longitudinal arch of the foot with only 10 pounds of loading force on the forefoot is simply only one of the many "loaded equilibrium positions" of the midtarsal and midfoot joints that will occur within the wide range of weightbearing activities performed by the human species on a daily basis.

 

Also, here is a link to Shephards paper from 1951 in which he describes the midtarsal joint as being uniaxial.

http://www.bjj.boneandjoint.org.uk/content/33-B/2/258.full.pdf html

I like this comment from towards the end: "It might be thought, therefore, that peritalar movement interferes with hinge movement at the midtarsal joint, but since both peritalar and midtarsal axes pass through d, the centre of the sphere defined by the talo- navicular joint, hinge movement at the midtarsal joint can occur whatever the position of the peritalar joint."

 

Simon,
Your drawing of the round ball and the wedge is a completely erroneous depiction of a calcaneus and the heel cup of an orthosis. I keep seeing that exact same argument made by a number of individuals but it is a false premise. Again, I must ask why it is okay for you and Kevin to use false models and yet you criticize others when their models aren’t completely accurate?

To begin with, the heel cup is nothing like a flat plane (i.e. wedge) in the frontal plane like you have drawn. It is concave with a lip at both the medial and lateral borders. Put your sphere in a rounded cup and you will have a more accurate picture of the heel cup. You chose a wedge to try to prove a point but in doing so, you are not representing reality and are distorting the truth by make a false point.

Next, you need to show sections of the heel cup in the sagittal plane since the heel is a complex shape and has an angle of inclination created by the inclination angle of the calcaneus and medially, by the beginning of the transition into the medial arch. The medial aspect of the heel cup has an anterior inclination angle. So you need to look at the heel in the frontal and sagittal planes to get an accurate representation of the interaction between the heel cup of an orthosis and the heel. I have attached a frontal plane photo of a cast of the exact same foot, one with a medial heel skive modification and one without it to demonstrate how inaccurate your graphic is. Will you now be good enough to stop using your drawing? You are welcome to use my pictures of real casts and orthoses to demonstrate reality.

 

Jeff, I appreciate that you are keen to have a "pop" since I have spent the last couple of days critiquing and pointing to errors in your fathers work, but to quote Daryl, you may want to "cool your jets" or as I prefer "wind your neck in". I did not make the drawings, they were from a 1961 paper by GK Rose. I suspect everyone else here will have already recognised that, I wonder why you did not? I was discussing GK Rose's contributions to foot orthoses therapy within the lecture and used some of his diagrams as illustrative points. The shape of the orthotic beneath the heel will be dependent upon the type of orthotic. A DC wedge for example will approximate a flat inclined plane, the Interpod prefabricated devices will too; the shape of a medial heel skive device will be different again as will a MOSI. Given that Rose was using a weightbearing casting technique, I should imagine the orthoses he made also had a relatively flat inclined plane within the heel cup- hence his diagrams (in fact if you bother to read the papers you'll see he gives diagrams of cross-sections of his orthoses. But to re-iterate, they were not my diagrams, they were from a lecture I was giving on the history of foot orthoses therapy. Now, perhaps if you go to the trouble to read the paper's from which the diagrams were taken which I've conveniently already attached for you, you will see that Rose was using the circular wheel as a "model" to explain how the calcaneus can rotate about an interface axis between it and the ground. When we look at the shape of medial tubercle of the calcaneus in the frontal plane, it actually makes for a good analogy; much better than pretending that the calcaneus rests on both the medial and lateral tubercles as I believe your father's book illustrated it... Anyway, I had chosen to speak about Rose's work within this lecture for a number of reasons, not least because he clearly recognised that the subtalar joint axis moved in-vivo as the foot pronated and supinated, and he'd also realised that wedging medial to the subtalar joint axis should be more effective in attempting to prevent the rearfoot from pronating than wedging both medial and lateral to the axis. This, it could be argued, forms the basis of the SALRE theory, the medial heel skive and the MOSI techniques-which in my opinion, was pretty forward thinking for 1961. I also drew comparison with some of Kevin's later diagrams which he made to exemplify similar points, hence my slide from the end of the lecture with Ecclesiastes 1:9. Embarrassed? You should be.

 

No! The caption directly above the picture says "Orthotic Design/Negative Model Acquisition. I don't know the exact context of your lecture but I keep seeing that same or a similar drawing used to attempt to "prove" that a functional orthosis can't possibly control STJ pronation because the heel is "round" and will roll off an inclined plane. The next slide with the same caption shows Rose using the MASS casting technique. Or is that a picture you inserted? I can't tell. But based on the context of the limited information you presented, it appears to me that you were making the point that some people believe that the MASS casting technique creates a better plantar contour for making an orthosis using the argument that a functional orthosis is similar to a varus heel wedge. Perhaps if you would have provided an explanation along with your slides I would have better understood what point you were attempting to make.

 

Daryl:

Due to the flurry of postings recently, and my busy schedule, I missed your question here.

In answer to your question regarding my negative casting technique that Drs. John Weed, Ron Valmassy, Chris Smith, John Marczalec, Lester Jones, Bill Sanner, Rich Blake and others taught me, here is what I do now.

I still use two 5" x 30" strips of plaster, have the patient supine, position the foot in neutral position or slightly pronated from neutral position for casting by grasping the 4th and 5th digits and loading the digits with a force that is directed superiorly toward the patient's head. However, I deviate from what I was taught by my professors during casting by now often plantarflexing or dorsiflexing the medial column depending on the patient I am casting.

In general, for children and teenage flatfoot patients, I plantarflex the medial column of the foot during casting to increase the medal longitudinal arch (MLA) height. For adults with pes cavus deformity, I will dorsiflex the medial column to lower the MLA height and preload the plantar fascia. For many older adults with flatfoot deformity that have compliant medial columns I will also dorsiflex the medial column to lower the MLA.

Therefore, Daryl, I use the parts of the neutral suspension casting technique that I like and discarded and then modified the parts I didn't like to optimize the foot orthosis therapy for my patients.

Good discussion.:drinks

 

Rob,

In your opinion, how has science changed the way in which podiatrists now examine, diagnose and treat foot conditions? Please be as specific as possible. Thanks.

 

Again, read Rose's paper. Yes he did advocate a casting technique with many similarities to the MASS technique, again this was discussed in the lecture, again this is why a picture of his casting technique from one of his papers was included in the slide and moreover why Ecclesiastes 1:9 was included at the end of the lecture. That you couldn't tell whether or not this was someone taking a MASS cast exemplifies the point, again for the record, he was advocating this in 1958-1961. The caption "Orthotic Design/Negative Model Acquisition" was there because those were two areas I believe Rose contributed to within the evolution of orthotic therapy and the two areas discussed and illustrated by those two slides within the lecture. I sincerely think you need to stop with the knee jerks and jumping to the wrong conclusions, Jeff. If you'd have asked me what points I was making with the slides rather than going on the offensive, I'd have explained it to you. The point being that there are several aspects of modern foot orthoses therapy which trace their origins back to earlier workers. In this case, earlier workers that were publishing prior to your father.

I've quickly airbrushed one of Rose's diagrams from my slide, compare this shape to your picture of the cross-section through the medial heel skive. Do medial heel skives offer greater supination moment to the foot than the rounded heel-cup in your other device? This, I believe is the point Rose was making in his diagram. If you look at the picture of the Schwartz meniscus which Rose employed in his second paper, you'll see that the cross-section would have not been too dissimilar to this. I also know that a later version "the Rose-Schwartz meniscus" was manufactured from Rohadur and included a medial longitudinal arch support as well as an asymmetric heel cup. Unfortunately I couldn't find a picture of this when I was making the lecture.

 

Simon, when I first replied I didn't realized that you had attached his papers to your next posting.

 

Yes, I believe they do. However, individuals like Ed Glaser have argued that the heel will slide off a medial heel skive and have used the varus wedge and sphere diagram in their argument. My apologies if I misinterpreted the intent of your posting. And yes, I was hastily skimming them.

 

Jeff, we've known each other long enough to know that it's just academic debate and sometimes it gets heated! Ed Glaser has made several statements, that doesn't mean he's right.:drinks

Great discussion. Here are a couple of further slides from my lecture. I think that by the end of the 1970's Carlson and Berglund were coming to similar conclusions that Rose had established back in 1961. Nothing new under the sun- feet are still flat and all these people, like many today, were all trying to stop them from being so flat.

 

One other comment/observation. People criticize the Root casting technique because they don’t believe that loading the lateral column with so little force will fully pronate the mtj to the end rom like ground reaction force can. However, some also plantarflex the 1st ray or medial column to increase the ff valgus attitude of the forefoot. I understand the logic of this increased valgus in the cast but plantarflexing the medial column does just the opposite of what grf does to the medial column in most feet. So the purpose of casting is not to replicate grf or the weightbearing position of the joints, it is to place the joints of the foot in a position that the practitioner believes will be most beneficial during casting so that the cast and resulting orthosis will influence the mechanical forces in a manner to best address the pathology in question.

 

The negative model just provides a starting point for the 3-dimensional shape of the finished orthotic, nothing more, nothing less. The finished foot orthosis doesn't hold joints in positions, all it can do is alter the reaction forces at the foot's interface with it. The shape of the orthotic is only one of three orthotic design elements which ultimately determine the kinetics at the foot-orthosis interface. This was one of my points yesterday- just because you cast a foot in a certain position, doesn't mean that the foot will adopt that position when standing on the orthosis. Think about it logically: why should it? The forces being applied to the foot during a non-weightbearing casting process are nothing like the forces being applied to the foot when standing on the finished orthosis. Reaction forces along with internal forces will determine the equilibrium positions of the joints (Kevin's point) so why on earth would we expect the foot to adopt the same position on the orthoses that it was in during casting when both the internal and external forces acting on the foot will be completely different between non-weightbearing casting and standing on the finished device? It's non-science to expect it to, if you ask me. To me that seems obvious.

Put another way, the only way I'd expect an orthosis to place the foot in the same position that it was cast in should be if the foot orthoses replicates precisely the magnitude and distribution of forces that the foot was subjected to during the casting process. I guess this is where systems like this come into play http://www.youtube.com/watch?v=qs77Qf--m68 Although once again, there is nothing new under the sun- here's yet another slide from my "evolution of foot orthotic therapy" lecture attached. This time it's George Ogden who in 1948 invented and patented a direct mold, foot alignment system for orthotic manufacture. But even then, once removed from the jig, the forces exerted at the foot orthosis interface will still not be the same as those exerted during the molding/ casting process since the force being applied by the jig will have been removed.

Personally, I start thinking about where I want the higher reaction forces and lower reaction forces at the foot-orthosis interface when I start to cast the foot. I have knowledge of how surface curvature will influence the load-deformation characteristics and ultimately the reaction forces at the foot orthosis interface, so I manipulate the foot into a position which I think will give me something close to the surface geometry I'm looking for in the finished device at it's interface with the foot- it'll save me time and work later, since unlike the majority of you, I manufacture all of my own devices.

Jeff, I went back through "neutral casting techniques" today. Much of the book concerns itself with "errors" in technique. Here's what I'd recommend you and anyone else who owns a copy of this book do: go back through the book look at all the "errors" listed in the book and think about how these "errors" might change the shape of the finished orthoses, then think about how this might change the load/ deformation characteristics of the devices at specific points at the foot-orthosis interface. Then stop thinking of them as "errors" and consider them as useful techniques that you can use to modify the design characteristics of the finished orthoses that you prescribe and manufacture. And that, even if I say so myself, is a pearl.

 

Simon, I already have. In the days of Rohadur orthoses, if you supinated (inverted) the ff of the negative cast, a triangular shape would often break off at the anterior, medial aspect of the device (size approx. 1"X1"X2"). It makes sense, if you increase the supination moments of the device the material needs to be capable of supporting the increased load. Feet with ff supinatus would also do the same thing but if you re-casted, the ff supinatus would then be less or absent. In addition, if you supinated the "oblique" axis of the mtj (i.e. adducted and plantarflexed the ff), the device would often break transversely just anterior to the rearfoot post (along the mtj). An acquired plantarflexed 1st ray would do the same thing, and if you re-casted, the degree of 1st ray plantarflexion would be reduced in the new cast. Most of these patients had some element of residual 1st ray plantarflexion, unlike ff supinatus that would more often completely reduce. So we knew how the casting position influenced the forces acting on the orthosis due to the breakage patterns in the devices and we could see how the orthotic forces influenced the soft tissue by the changes that occurred in the plantar contour of the foot.

We would often call the practitioner and tell them when we suspected a casting error based on the appearance of the cast. This gave them an opportunity to re-cast. If they chose not to re-cast, we would make a note of this on their copy of the Rx. If the device broke as we suspected it would, we would refer them to our note on their returned copy of the Rx form in their patient's chart. After that happened a few times, most practitioners became very appreciative of our proactive advice. We always recorded the ff to rf measurements from he cast on the Rx so we could tell from the Rx if the patient had an inverted or everted ff. Since polypropylene and composites don't break like acrylics, this is less of an issue plus it allows practitioners to do things in their casting and Rx that would have resulted in orthotic shell failure with acrylics, such as Rohadur and Polydor. I wrote about all this way back on the Podiatry Mailbase and in the early days of the Podiatry Arena.

 

Oh well, Ecclesiastes 1:9 "nothing new under the sun".

Anyway, last couple of slides I'll post from my lecture- promise. For the record, there were more slides dedicated to Merton Root and his colleagues in this lecture than any other individual or group. What you should take into consideration is that at this particular conference I was also giving a lecture on "myth's in podiatric biomechanics", one of which was the "locking" of the midtarsal joint...