Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

The "Midtarsal Joint"...

Discussion in 'Biomechanics, Sports and Foot orthoses' started by admin, Jan 13, 2006.

  1. admin

    admin Administrator Staff Member


    Members do not see these Ads. Sign Up.
    Its one of those joints that is subject to so much ongoing debate and discussion ... here is Chris Nester's attempt to, at least, get everyone speaking the same language:
    Clinical and Experimental Models of the Midtarsal Joint
    Proposed Terms of Reference and Associated Terminology
    Christopher J. Nester and Andrew H. Findlow
    Journal of the American Podiatric Medical Association
    Volume 96 Number 1 24-31 2006
    What say you?
     
  2. Chris Nester visited Sacramento in April 2001 and I invited him over my house so we could talk biomechanics over a beer or two. In our long discussions over his earlier paper on the midtarsal joint and on the problems with previous podiatric descriptions of the midtarsal joint, we both agreed that the paper he and Andrew just published on the reference axes of the midtarsal joint needed to be written. It is very satisfying for me, for the sake of podiatry, to finally see this paper published. Nice also to see something as good as this paper begin from a conversation over a few brews in my living room.

    Congratulations to Chris and Andrew on their groundbreaking work on the biomechanics of the midtarsal joint. Now, no more discussion of the longitudinal and oblique midtarsal joint axes......please!!!
     
  3. The single axis model of the midtarsal joint makes life easier when trying to understand and teach mechanics of the midfoot. It was what we needed to move away from the untruth of oblique and longitudinal model. However, it should be remebered that it is a conveniant simplification of the truth and not the truth in itself. That is, while the movement seen about the midfoot can be thought of as occuring about one axis, in reality each joint must have an instantaneous centre of rotation and/or translation.
     
  4. Good point, Simon. Since we know that the navicular and cuboid do not move as a solid rigid unit (i.e. we know there are some slight movements between the two bones), then the one axis model of the midtarsal joint is an approximation of reality, but not absolute reality. However, the question must be asked, for the sake of clinical descriptions, what type of modelling approach should be used in teaching midtarsal joint biomechanics to students and practitioners?

    In my opinion, the one axis model of the midtarsal joint that moves continually in space during gait is a far better approach than the two axis, oblique and longitudinal axis, approach. Also, I greatly favor Nester and Findlow's three reference axes of the midtarsal joint, since this is what we agreed on would be the best approach for podiatry nearly five years ago.

    As we become more sophisticated in our technology, the midtarsal joint axis suggested by Nester and Findlow will probably need to be replaced since we may someday be able to clinically detect how the navicular moves relative to the cuboid. However, I seriously doubt that this technological advance will occur within the next 20 years so we can safely teach the one axis model of the midtarsal joint with the qualification that it is not not absolute reality, but a very good approximation of reality.
     
  5. Kevin,
    No real argument from me. What I find interesting is that while Chris and Andrews work seems to have been taken on board by many within the podiatric community, the more accurate work of Van Langelaan(?) which describes the centres of rotation for both the CCJ and TNJ as individual joints seems to have, in the main, been ignored.

    How much more complex is it to take moments about one axis or two axes so long as we know roughly were those axes are in space at given point within the gait cycle?

    Of note, I seem to recall that when I last spoke to Chris about their model, he seemed to be pulling back from this view point and indicated that there may have been some problems which had been overlooked at the time of publication, which he himself had now realised. Or perhaps it was the fact that we had drunk too much?
     
  6. Chris Nester lives in the world of research where he is currently working on validating a model for the foot using his recent work in Sweden, where they drilled pins into bones of live subjects and measured individual bone motions. I imagine that his newer research has made him realize that the cuboid and navicular do move independently of each other (about 3-5 degrees if I remember correctly), but could not see this clearly until he went to Sweden, where they allow live subjects to have pins drilled into the bones of their foot.

    However, from my standpoint as a clinician, I think that to break up the midtarsal joint into two joints now will be much too complex for 99% of the podiatrists, and so even though it may be more accurate, it will be so complex that it will hinder a broader understanding of the joint. In addition, we currently don't have sufficient research to begin to know how these joint axes may move during weightbearing activities such as walking or running. Maybe Chris and coworkers will provide us this information within the next year.

    Right now, it will be a major battle to get all the podiatry schools to stop teaching the longitudinal and oblique midtarsal joint model so that the more recent midtarsal joint research may be highlighted.

    For my part, I am very interested in the three reference axes of the midtarsal joint for describing the kinetics of the midtarsal joint for the many pathologies that affect the midtarsal joint. Here is where, I believe, the clinical "paydirt" will be found in this "one axis approach". I have already begun to use this three reference midtarsal joint axis type of approach in my lectures and writings on functional hallux limitus, plantar fascial functions, and posterior tibial dysfunction. It is far superior to any other approach in teaching the kinetics of the midtarsal joint.
     
  7. Ian Linane

    Ian Linane Well-Known Member

    Ok guys help me out here

    This approach is new to me so can it be explained in a way that someone new to the single axis MTJ might grasp.

    Thanks Ian
     
  8. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Ian - may want to have a look at:

    CB Payne: The role of theory in understanding the midtarsal joint. J Am Podiatr Med Assoc 2000 90: 377-379.

    While I did not discuss a one axis model, did look at why the 2 axis model is wrong, and examined why we still used it as an aid to learning and understanding, but its still a "convenient theoretical fiction"....the problem is most still take it as fact - just look how old the references are now ... don't figure:rolleyes:
     
    Last edited by a moderator: Jan 14, 2006
  9. Here are the main points that Nester and Findlow are trying to make:

    1. There can not be two axes of rotation existing at any one time to describe the rotational motion of one rigid body relative to another rigid body so that the description of two midtarsal joint axes that exist simulataneously (i.e. oblique and longitudinal) can not be an accurate description of the motion that occurs across the midtarsal joint.

    2. If we consider the calcaneus to be one rigid body and the cuboid and navicular to be another rigid body [the cuboid and navicular only move about 3-5 degrees relative to each other so we can reasonably consider them collectively to be one rigid body] then any rotational motion between the calcaneus and cuboid-navicular can be described as occurring at one axis of rotation.

    3. Since research has shown that this one axis of rotation of the midtarsal joint is not fixed in space but rather is continually moving in space during weightbearing activities, it is convenient to describe it's spatial location at any time in a three axis coordinate system, which Chris Nester and I agreed could be reasonably called the "reference axes for the midtarsal joint". These axes are the medial-lateral midtarsal joint axis, the vertical midtarsal joint axis and the anterior-posterior midtarsal joint axis.

    4. Both the kinematics (i.e motion) and kinetics (i.e. moments) acting across one axis of the midtarsal joint can be easily described using this three axis reference system for the midtarsal joint, understanding that these axes are only reference axes, and not the actual axes of motion. However, these reference axes allow for easy description of a component motion or a component moment of the resultant motion or resultant moment that is occuring at any time across the single axis of rotation of the midtarsal joint.

    5. The axis of motion of the midtarsal joint is dependent on the motion of the cuboid-navicular relative to the calcaneus and is not a fixed axis, as was previously described for the oblique and longitudinal axes. Therefore, depending on the magnitude, direction, line of action and point of application of both the external forces acting on the foot and internal forces acting within the foot, this axis of motion will vary widely from one individual to another, and will move in space during different weightbearing activities.

    When Chris and I actually were actually first talking about these concepts nearly five years ago in my living room, I said that I was going to write a paper on the kinetics of the midtarsal joint, using these reference axes that we came up with, after Chris and Andrew's wrote this paper that introduced and described the reference axes. So far, I haven't taken the time to do this important paper, but have used the concept of the reference axes of the midtarsal joint in lectures and items I have published over the past few years.

    Hope this explains our views on the way the biomechanics of the midtarsal joint should be described for now and in the immediate future in lectures and papers on foot biomechanics.
     
  10. Ian Linane

    Ian Linane Well-Known Member

    Hi Kevin and Craig.

    Thanks. Helpful.
    Looks like I will have to bring the little grey cells out of retirment.

    Ian
     
  11. Jeff Root

    Jeff Root Well-Known Member

    The midtarsal joint is actually comprised of two individual joints (ie. the calcaneocuboid joint and the talonavicular joint). Do the TNJ and CCJ have independent axes of motion that can be resolved into a common axis? Can there be independent motion of either the TNJ or the CCJ without simultaneous motion of the other? Perhaps part of the problem is in attempting to use the term midtarsal joint to describe two individual joints that may not always display dependent motion. Therefore, one might argue that the MTJ has one axis of motion while the CCJ and TNJ have two axes of motion. Semantics?
     
  12. Jeff,

    I agree with you. This is the point I was making. If we look at motion of the midfoot, i.e. the MTJ then we can quite happily model this as having one resultant axis. But if we consider the TNJ and CCJ as seperate entities and accept that some movement occurs between these then we must look at the axis of each of the joints seperately as the "swedish" research has done. It should be noted that this is not the same as the oblique/ longitudinal model.

    Out of interest are there any other precedents for clumping multiple articulations together in this way?

    Best wishes,
    Simon
     
  13. Jeff Root

    Jeff Root Well-Known Member

    Simon,

    From both a clinical and educational perspective, the use of the terms longitudinal and oblique axis of the MTJ are used as a reference to relate MTJ motion to the cardinal body plane. The longitudinal axis is a reference for inversion/eversion motion at the MTJ while the oblique axis is a reference for adduction/plantarflexion of the MTJ and abduction/dorsiflexion of the MTJ. We don't necessarily need new terminology to describe MTJ motion. We can easily replace these terms as follows:
    1. replace the term "supination about the longitudinal axis of the MTJ" with inversion at the MTJ. Note single plane motion, not biplane or triplane motion.
    2. replace the term "pronation about the longitudinal axis of the MTJ" with eversion of the MTJ. Note single plane motion, not biplane or triplane motion.
    3. replace the term "supination about the oblique axis of the MTJ" with simutaneous adduction and plantarflexion at the MTJ. Note biplane motion, not single or triplane motion.
    4. replace the term "pronation about the oblique axis of the MTJ" with simultaneous abduction and dorsiflexion of the MTJ. Note biplane motion, not single or triplane motion.


    As one can see, it is much more convenient and less cumbersome to say "MTJ oblique axis supination" than it is to say " simultaneous adduction and plantarflexion at the MTJ". The original terminology makes it convenient to explain simultaneous closed chain motion at both the STJ and MTJ. For example, I could say that during closed chain STJ pronation, the talus adducts and plantarflexes and the calcaneus everts while the MTJ supinates about the longitudinal axis and pronates about the oblique axis. I could replace these terms with more accurate terminology and say that during closed chain STJ pronation, the talus adducts and plantarflexes and the calcaneus everts while the midtarsal joint inverts, abducts, and dorsiflexes. However I don't know that anyone could exactly describe the motions of the cuboid and navicular at that time.

    The MTJ is highly complex. For example, if the calcaneus and cuboid evert together and the cuboid simultaneously abducts and dorsiflexes on the calcaneus at the CCJ, and if the navicular is dorsiflexed relative to talus by ground reaction acting on mets 1 through 3, then this results in a relative inversion of the forefoot (ie. a measurement of mets 1-5 will be more inverted to the heel). In other words, the sagittal plane motion of dorsiflexion of the navicular will result in closed chain inversion of the forefoot on the rearfoot when the amount of navicular dorsiflexion exceeds the amount of dorsiflexion of the cuboid (which it typically does). Hence, sagittal plane motion can contribute to the appearance of frontal plane motion at the MTJ when the more highly mobile TNJ allows the navicular and medial column to move more in the direction of dorsiflexion than the cuboid can allow the lateral colum to move in the sagittal plane. Therefore, frontal plane motion at the forefoot resulting from MTJ motion doesn't necessarily occur about a longitudinal axis or any other axis that we might normally relate to. The MTJ is a complex little bugger!

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722
    (877) root-lab
    www.root-lab.com
     
  14. Jeff,

    My understanding of the single axis model of the MTJ is that there is one moving axis, not an "oblique axis" and a "longitudinal axis", and that the spatial location of the axis is dependent upon the force applied to the MTJ. Describing this as "the longitudinal axis" and "the oblique axis" makes it sound like there are two axes. From what I can recall from the paper, during gait the single axis appears to move through a wide arc of roughly 90 degrees, from a position were it makes a small angle with the frontal plane (thus a large angle with the sagittal plane) during loading response to a position were it makes a small angle with the sagittal plane (and thus a large angle with the frontal plane) during midstance and back to making a small angle with frontal plane during propulsion. I don't recall its relative position to the transverse plane at these times. But I have just managed to describe the single axial position without using the words oblique axis and longitudinal axis
    ;)


    If we apply the same logic to the STJ as seems to be being applied to the MTJ we could also start talking about an oblique axis and longitudinal axis as it also swings from extreme to extreme in its planal dominance during pronation and supination. I'm not suggesting that we do this BTW.

    You're right though Jeff, the MTJ is a bugger.

    Best wishes,
    Simon
     
  15. Jeff Root

    Jeff Root Well-Known Member

    Simon,

    Sorry for the confussion. When I said we don't necessarily need new terminology to describe the MTJ, I meant that we could use the existing terms inversion/eversion, adduction/abduction, and plantarflexion/dorsiflexion to describe the motion. We don't necessarily need to use the words supination and pronation, especially since it is technically impossible to have simultaneous supination and pronation of a single joint or single joint complex. Why, because supination is simultaneous adduction, plantarflexion, and inversion while pronation is simultaneous abduction, dorsiflexion, and eversion. Hence, the MTJ can't technically supinate and pronate at the same time. So I was attempting to agree with you but at the same time, explain the conceptual benefit and convenience of the two axis model. A single axis model can be used to describe MTJ motion but then we can't use the terms supination and pronation to describe closed chain function.

    For example, what do you call it when during closed chain STJ pronation, the forefoot abducts, dorsiflexes, and inverts on the rearfoot at the MTJ? That's neither supination nor pronation. There are times when the MTJ can actually supinate and proante, but probably only during open chain motion. The typical motion that occurs at the MTJ during closed chain motion can't be described as supination or pronation.

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722
    (877) root-lab
    www.root-lab.com
     
  16. javier

    javier Senior Member

    I would like to add my contribution to this discussion. On the Chris Nester's paper it was stated that:

    "Contemporary data have shown that it is possible to describe the kinematics of the midtarsal joint by modeling the navicular and cuboid bones as one rigid body moving relative to the calcaneus, and under such conditions the rotation of this body relative to another can occur only around one instantaneous axis of rotation."

    From my point of view, here is where the discussion's core lays: although it is possible and accurate to consider MTJ joints as a rigid body, is it "real"?

    Feet are flexible bodies and symptoms usually appear when there is an increase or decrease of flexibility beyond "normal" ROM.

    Thus, both Jeff (MTJ is is highly complex) and Kevin (one axis model) are right depending on the "rigid body" vs "flexible body" approach. And, both models are useful for different purposes.

    Javier
     
  17. Javier, Jeff and Simon:

    Truly the central point of the discussion is whether we should model the midtarsal joint as having the cuboid and navicular moving independently of each other or moving together, as a unit, which then would allow the cuboid and navicular to be modelled together as a single rigid body.

    From reading nearly every research paper that has been written on the midtarsal joint (there are not that many, by the way), I think we can reasonably, at this point in time, model the cuboid and navicular as moving as one unit as a rigid body. I recommed this be done, with the understanding that we can separate these two bones into two rigid bodies once we have more research data that allows us to reliably separate the two bones. This will probably take at least 10-15 more years of research, from my estimates.

    One must remember that even though it is easy for us to think of a bone as one rigid body, even a bone like the second metatarsal is not a true rigid body since it bends under loading forces. I would estimate that the distal end of the 2nd metatarsal probably bends at least 1 degree relative to the proximal end under heavy loading forces, and this is a bone that we mentally already readily accept as a "rigid body".

    The question then becomes whether the 3-5 degrees of motion between the navicular and cuboid is that much greater than the 1 degree of motion within the 2nd metatarsal, which we already accept as being a rigid body, to make the rigid body assumption of the navicular and cuboid no longer valid. I don't think so, especially for the purposes of clinicians trying to better understand midtarsal joint kinematics and kinetics.

    I strongly believe that it is much more important for clinicians to throw the oblique and longitudinal axis models out the window and try to understand the recent research by Nester and others so that they can better understand the reality of how the foot works during weightbearing activities. The little motion that occurs between the navicular and cuboid, in my opinion, should not be a significant barrier in appreciating the importance of this landmark research regarding midtarsal joint function.
     
  18. Kevin, Jeff and Javier

    My view is that time will show that the movement between the cuboid and navicular is significant. Joints exist for a reason. Why don't we have one bone bar, rather than two very different bones?

    However, at this point in time using the one, moving axis model of the MTJ makes more sense (to me). But we must interpret this correctly. If we show the foot in a quasi static analysis, the axis should be in the correct (approximate) position for that point in the gait cycle. That is if the foot is shown to be at midstance the axis at this point should be shown to be making large angles with frontal plane as in the Nester data. If the foot diagram for the analysis represents loading response or propulsion then the axis should be shown to be making a large angle with the sagittal plane. In other words the axial position is phase of gait dependent. What we do not seem to know from the Nester data is the position of the axis in static bipedal stance.

    Best wishes,
    Simon
     
    Last edited by a moderator: Jan 18, 2006
  19. Jeff Root

    Jeff Root Well-Known Member

    Kevin,

    If the cuboid and navicular were a rigid body we would probably see significant reductions or changes in the nature of MTJ and STJ motion. The cuboid must be able to evert with the calcaneus during closed chain STJ pronation while the navicular simultaneous inverts. This is part of the mechanism that converts the foot from a rigid lever to a mobile adaptor. When this occurs, the wedge shaped cuneiforms fan out further making the foot more mobile (ie. the foot splays). Looking at the cuboid and navicular as a rigid body doesn't help us explain the import change in overall foot stiffness that occurs between the foot when it goes from a pronated to a supinated position.

    Looking at the cuboid and navicular as a rigid body may be useful if one is attempting to compare the relationship between the plantar plane of the forefoot and the rearfoot as a unit and doesn't care about the finer elements of osseous motion. However, clinically variations in the nature of MTJ motion from one individual to the next are extremely interesting and significant. Variations in the range and direction of motion at the MTJ within the various cardinal body planes has a dramatic effect functionally. I'm not sure we can appreciate these functional variables when the navicular and cuboid are seen as a single unit. That doesn't mean the model doesn't have purpose, but like the two axis model it doesn't completely reflect reality.

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722

    (877) root-lab
    www.root-lab.com
     
  20. Kevin and Jeff,

    I've had chance to review some of the midtarsal joint literature today and went back the the Van Langelaan data and also the Ouzouman and Shereff study. It is difficult to draw strong conclusions due to the varying methodologies employed but Ouzouman and Shereff noted a RoM of only 7 degrees at the TNJ and only 2.3 degrees at the CCJ when a relatively small dorsiflexion/ plantarflexion load was applied. When an inversion / eversion load was applied TNJ ROM was 17.7 degrees and CCJ was 7.3 degrees.

    Van Langelaan noted a range of motion between the cuboid and navicular varying between 3.9 degrees and 6.8 degrees. My conjecture is this: if the cuboid and navicular are considered as a rigid body so too should the calcaneus and cuboid since the ROM at the CCJ is at best only just over a degree greater than between the cuboid and navicular.

    How many degrees ROM do we need before 2 objects cannot be considered as a rigid body?

    Best wishes,
    Simon
     
  21. Ian Linane

    Ian Linane Well-Known Member

    Whilst still very new to this concept I am curious as to, when speaking of the rom at these joints, whether consideration is given to the differing rom in any one joint over a 12 and 24 hour period. For example, if there is 3-4 degrees of rom available and people feel that is not so significant as to prevent the joints being considered, theoretically, as functioning as one, what are the implications to this theory if the respected joints gained a further couple of degrees of rom throughout the day and then maybe dropped down to only 1-2 degrees of rom in early morning.

    Would this make the new concept, because of the variation in rom, less /more valid, or reduce it to an arbitrary approach to try and make up for disatisfaction with the existing LMTJ and OMTJ approach. Honestly curious.

    Or am I showing ignorance here?

    Ian
     
  22. Jeff Root

    Jeff Root Well-Known Member

    Ian,

    You don't have to wait 12 to 24 hours to experience a change in MTJ ROM. There is an instantaneous change in the range and direction of motion at the MTJ as the position of the STJ is altered. As the STJ moves, the positional change between the talus and calcaneus directly causes a change in the range and direction of potential motion at the MTJ. This can be easily demonstrated clinically as follows (right foot used in the example):

    Place the patient in a supine position with their right foot extended off the examination chair but have the chair (or table) support their lower leg (like in the supine casting technique). With your left hand, place your thumb on the plantar aspect of the 4th/5th met heads and grasp the 4th/5th met heads between your thumb and index finger. Fully supinate the foot at the STJ. With your right hand, grasp the medial and lateral aspect of the calcaneus and hold it in the fully supinated position. With your left hand laterally oriented, place your thumb on the plantar surface of the foot directly inferior to the cuboid and navicular. Then place your 2nd and 3rd fingers on the dorsum of the foot on the dorsal aspect of the cuboid and navicular. While stabilizing the calcaneus with your right hand, move your left hand in the direction of plantarflexion/dorsiflexion, adduction/abduction, and inversion/eversion while moving the cuboid and navicular as a unit. Alter the direction of applied force in each cardinal plane as you observe the motion of the forefoot in the open chain. In the average MTJ, you will find that the greatest range and freedom of motion occurs when the forefoot is moved in the direction of simultaneous adduction and plantarflexion and simultaneous abduction and dorsiflexion.

    Next repeat this exact same process with the STJ in a fully pronated position. You will notice a dramatice increase in the ROM and direction of motion available at the MTJ when the STJ is pronated versus when it is supinated. There is a direct correlation between the potential range and direction of motion at the MTJ and the corresponding position of the STJ. For example, it is very apparent that there is more transverse plane motion of the forefoot available at the MTJ when the STJ is pronated than when it is supinated. Therefore, how can one model the cuboid and navicular as rigid unit when the nature of motion at the MTJ is positionally influenced and changes as the position of the proximal segments is altered? In essence, the MTJ changes shape in response to proximal segment changes.

    The clinical technique I described helps demonstrate the mobile adaptor rigid lever concept. Some have described it as a locking and unlocking of the MTJ but that isn't appropriate terminology. Better terminology would be increased motion potential and decreased motion potential.

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722

    (877) root-lab
    www.root-lab.com
     
  23. Ian,

    What you should appreciate is that due to the nature of this research, much of it is has been performed on cadaver specimens. Hence little consideration is given to "warming up" of ligamnets. As such results are somewhat artificial. Moreover, the nature of the research also means that sample sizes are small, hence our certainty of the accuracy of the findings is not necessarily too good. But your point is well made. There are many factors in this kind of research which are "ignored" because they are difficult to control or achieve.

    One small step....
     
  24. efuller

    efuller MVP

    If I were designing the foot, I would make it solid. However, the foot is the product of evolution and it was not designed ideally. If you look at horses they evolved from multiple toes to a single toe. Their survival was probably more dependent upon speed than our ancient ancestors. I can’t really think of a reason why we would need to have motion between the navicular and the cuboid. This motion may be just leftover from where the ideal situation would be fusion, but the amount of motion left is good enough evolutionarily for most of us to pass on your genes.

    On the idea of how much motion allowed constitutes enough to consider two separate bones a rigid body. Why don’t we just go by the amount of motion that we can see with the naked eye? When you grab a foot and manipulate it, you can easily see plenty of motion between the forefoot and rearfoot at the midtarsal joint. I’m not sure that you can detect any amount of motion between the navicular and cuboid with the naked eye when you try to. I guess the answer to this question depends on what question you are trying to answer. There might be some very detailed finite element analysis that would need this information. However, the additional data gained from this effort might be below the measurement error in the surrounding joints. That is to say having this knowledge may not add to accurate predictions with the use of a model of foot. To make life easier you make assumptions like the cuboid and navicular can be assumed to be a rigid body. However, you should check your assumptions. Clinically, I think that we can treat them as a rigid body.

    Simon also mentioned the motion found in the CC joint in the Van Langalaan paper. As I recall this was a weight bearing test and this would prevent a significant amount of motion in the plantar flexion dorsiflexion direction. The amount of motion measured in this manner is a minimum; it is possible that there is more.

    Simon also asked if there were any articles that ignored motion of one or more joints. There was a paper by Hinterman and Nigg about the lever arm of tendons about the “ankle joint complex”. This paper essentially treated the complex as a single joint.

    I haven’t read the Nestor paper yet, but I hope they talked about envelope of motion. To understand joint range of motion you have to understand the anatomical structures that limit the motion. The bones will move relative to one another until something stops them. As you move the joint in all directions the motion will be limited, sometimes sooner and sometimes later depending on the restraining structures. This explains the motions that are seen. In the single axis model, during gait, there is initially mostly frontal plane motion and then later there is mostly transverse plane motion. There is range of motion available in both of these directions and this range is allowed by the restraining mechanism.

    Another reason to search for the axis is that it may aid in understanding and calculating moments. Yes, you can calculate moments about an axis. but just because there is motion in a certain direction, does not mean that is the direction with the greatest moment. In propulsion, the greatest moments will be applied to the medial lateral axis whereas the greatest motion may be about the vertical axis. So, it is important to think of moments separately from motion in some instances.

    Eric
     
  25. Eric,
    I read somewhere that of all the bones in the human foot, it is the cuboid which shows the greatest difference from that of our ancestors. This would lead one the conclusion that the human cuboid is required for bipedal locomotion and standing. Thus I am not sure your argument holds true. But of course we are still evolving. Question, how frequently do we see a coalition between the navicular and the cuboid? Moreover, if we follow your line of thought, is the motion at the CCJ "left over" too since ROM here is hardly greater?

    >>>Simon also mentioned the motion found in the CC joint in the Van Langelaan paper. As I recall this was a weight bearing test and this would prevent a significant amount of motion in the plantar flexion dorsiflexion direction. The amount of motion measured in this manner is a minimum; it is possible that there is more<<<

    Actually the dorsiflexion/ plantarflexion motion at the CCJ which I mentioned previously was data from Ouzounian and Shereff. And as I recall, this paper artificially loaded specimens while the Van Langelaan study embeded markers in live subjects. Thus, both studies attempted to measure closed kinetic chain motion. But the loading in the Ouzinian study was a little weak!! Not withstanding then, the ROM at the CCJ appears little more, if at all, greater than that between the navicular and the cuboid. Perhaps I am missing your point Eric? Personally I am interested in weightbearing motion and not so interested in non-weight bearing motion. Could you explain?

    Let me state my position once again as it seems I am being drawn as the guy standing against the single axis model. I think for now the single axis model is a good approximation and makes the teaching of MTJ mechanics a whole lot easier. But it is not the truth :cool: And we all know that really.

    Best wishes
     
  26. It's nice to see Simon Spooner, Eric Fuller and Jeff Root at it again discussing the midtarsal joint....now all is right in the podiatric biomechanics world. And other good news is that Chris Nester has promised me that he would take some time within the next week to discuss his midtarsal joint research on Podiatry Arena. :D

    Simon, I am in basic agreement with you. Certainly your point is valid that we know that the cuboid and navicular to have some movement between them and that this motion is necessary for normal function of the foot. However, as Eric mentioned, we can probably now consider the cuboid and navicular to collectively be one rigid body when we discuss the midtarsal joint since this greatly helps simplify our discussion of midtarsal biomechanics, and foot biomechanics as a whole, considering our current level of knowledge.

    Jeff, the point is not whether I agree that the cuboid-navicular movements are important or not, since I know they absolutely are important to have normal foot function. However, what I am advocating is for us to take "baby steps" in describing midtarsal joint biomechanics instead of going full into trying to describe and understand the complicated biomechanics of the calcaneo-cuboid, talo-navicular, calcaneo-navicular joints separately during weightbearing activities. Since we don't have any good data yet on live subjects that informs this approach, I think it would be ill-advised for us to try and discuss it, except theoretically.

    I favor, rather, as Eric suggests also, of modelling the foot differently depending on what subject that I am trying to discuss. In my papers on subtalar joint (STJ) axis location, STJ rotational equilibrium, Blake inverted orthosis and medial heel skive techniques, I modelled the talus and tibia to be a single rigid body [the talo-tibial unit] so that I could discuss the biomechanics of the STJ with more clarity (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987; Kirby KA: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989; Kirby KA, Green DR: Evaluation and Nonoperative Management of Pes Valgus, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchill-Livingstone, New York, 1992; Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992; Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001).

    In my newsletters and lectures on the relationship on arch flattening and functional hallux limitus, I modelled the rearfoot to be one rigid body, the forefoot (excluding the digits) to be another rigid body and the hallux and digits to be another rigid body (Kirby KA.: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997, pp. 141-152). This was done to help clarify my mechanical discussion of the sagittal plane kinetics of the ankle, midtarsal and metatarsophalangeal joint and the relationship of longitudinal arch height to functional hallux limitus.

    In addition, I have used numerous other models in my newsletters and newsletter books that were created for the sole reason of making the complex biomechanics of the foot and lower extremity less difficult for the average podiatrist so that they could better understand the mechanical basis of the pathologies that they treat on a daily basis.

    Now, considering the educational benefits that these modelling approaches (i.e. using rigid body assumptions where we know there is a movable joint) have had for the average clinician to better understand foot and lower extremity biomechanics, I don't think that it is now difficult to see the educational benefit of modelling the cuboid and navicular as one rigid body when we discuss midtarsal joint biomechanics. The precedent of modelling a group of more than one osseous structure of the foot and lower extremity as one rigid body has been set within the podiatric literature now for the past 19 years. These modelling techniques will continue to be utilized by those who are intent on optimizing the transfer of foot and lower extremity biomechanics knowledge to students and clinicians for years to come.
     
    Last edited: Jan 18, 2006
  27. Jeff Root

    Jeff Root Well-Known Member

    Kevin,
    I guess only time will tell if modelling the navicular and cuboid as a rigid body will improve our understanding of MTJ function. I agree that we need different models of varying complexity for different purposes. What the model fails to demonstrate is the concept of independent medial and lateral column movement, which I feel is important even at the more basic level. Let me use the adult acquired flatfoot in my example since it is a common and significant adult onset biomechanical problem. The adult acquired flatfoot seems to be an event that originates in the medial column. During normal gait, the head of the talus appears to move more in the sagittal plane than the anterior aspect of the calcaneus. As the head of the talus adducts and plantarflexes the anterior aspect of the calcaneus everts with the cuboid as the cuboid dorsiflexes on the calcaneus. As the head of the talus plantarflexes, the navicular plantarflexes but to a lesser extent than the head of the talus which results in relative dorsiflexion of the navicular. What would historically be called long axis supination of the MTJ is probably a varus rotation of the navicular that acts to splay the medial column as vertical ground reaction forces increase at the distal forefoot (ie. met heads).

    In the adult acquired flatfoot, the loss of medial column integrity is evident and a varus attitude of the navicular can be demonstrated by the tuberosity of the navicular which becomes more medially and less plantarly directed. The medial tuberosity is an attachment for the posterior tibial. The forefoot supinatus seen in these individuals may likely originate, in part, by a varus rotation of the navicular relative to the cuboid. Interestingly enough, when the 1st met is dorsiflexed by ground reaction force, it also inverts. Therefore frontal plane motion of the 1st ray and navicular are connected and are highly significant in terms of 1st ray function.

    As we have discussed many times before (I think Chris Nester stressed this point originally), it is the motion that describes the axis. Therefore in any study that considers the axis of the MTJ, we must look at the forces applied. The typical motion between the forefoot and the rearfoot which is driven proximally by the STJ direction of motion and the distally by the interaction of the supporting surface consists of closed chain STJ pronation and supination, the net effect which is: 1.closed chain STJ pronation = abduction/dorsiflexion and inversion of the forefoot on the rearfoot and 2. closed chain STJ supination = adduction/plantarflexion and eversion of the forefoot on the rearfoot. Because the forefoot must be able to adapt to variances in terrain, the forefoot can also 1. abduct, dorsiflex, and evert (ie. pronate) and 2. adduct, plantarflex, and invert (ie. supinate).

    I believe the two axis model was employed to show the independant frontal plane motion at the MTJ. The single axis model can be used to show the net effect of the motion and in that sense is more accurate. It doesn't help in understanding the individual osseous movements which create the motion the net motion of the forefoot.

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722

    (877) root-lab
    www.root-lab.com
     
  28. efuller

    efuller MVP

    I believe the literature sited said that the CC joint is the most variable. Some are flat some are "s" shaped in the lateral view. So, I agree that it is quite variable. Pardon my theorizing, but I was assuming that our hands/ feet/ paws started more mobile and have become less mobile over evolutionary times. The horse went from many toes to one toe. I may be completely off on this one, I'm just thinking out loud.

    I agree that the cuboid is needed for locomotion. However, my point was that we may not really need motion between the navicular and the cuboid. What purpose does this motion serve?

    [/QUOTE]
    >>>Simon also mentioned the motion found in the CC joint in the Van Langelaan paper. As I recall this was a weight bearing test and this would prevent a significant amount of motion in the plantar flexion dorsiflexion direction. The amount of motion measured in this manner is a minimum; it is possible that there is more<<<

    Actually the dorsiflexion/ plantarflexion motion at the CCJ which I mentioned previously was data from Ouzounian and Shereff. And as I recall, this paper artificially loaded specimens while the Van Langelaan study embeded markers in live subjects. Thus, both studies attempted to measure closed kinetic chain motion. But the loading in the Ouzinian study was a little weak!! Not withstanding then, the ROM at the CCJ appears little more, if at all, greater than that between the navicular and the cuboid. Perhaps I am missing your point Eric? Personally I am interested in weightbearing motion and not so interested in non-weight bearing motion. Could you explain?
    [/QUOTE]

    The motion seen between these joints may be magnified by the parts distal to these bones. When the cuboid adducts on the calcaneus the entire forefoot moves through the same number of degrees and there is more distal motion further away from the axis of rotation. Motion between the cuboid and Navicular is not magnified in this fashion.


    The van Langaalan study was done on cadavers in a loaded aparatus. My point is that you will see more plantar flexion range of motion when the foot is unloaded. So, you could find more motion than was found in the study.

    Whether or not you look at the range of motion loaded or unloaded depends on the research question. I would agree that the loaded motion might be more important than unloaded motion. However, if we want to look at stress, motion may not be that relevent. Sagital plane stress (thelargest magnitude stress) would be related to moments about the medial lateral axis of the joint regardless of what motion occured in the transverse plane.

    Eric
     
  29. I agree that the independent sagittal plane movement of the metatarsal rays would be one instance in where I would want the navicular separated from the cuboid in a model. As you have described, the medial and lateral columns have independent motion. However, we still don't really know if the navicular is causing most of this movement of the medial column relative to the lateral column or whether it is the joints distal to the navicular that cause the majority of the movement. I suspect that it is the medial metatarsals and cuneiforms dorsiflexing that cause the vast majority of what we previously called "long axis supination" and not an inversion or dorsiflexion motion of the navicular relative to the cuboid that causes this movement of the metatarsal heads relative to the rearfoot.

    In posterior tibial dysfunction (PTD) there are a cascade of pathological mechanical events that occur:

    1. Medially deviated STJ axis pre-exists in the foot that leads to increased magnitudes of tensile forces within the posterior tibial tendon during weightbearing activities.
    2. Increased tensile stress within posterior tibial tendon causes plastic deformation, tearing or complete rupture in the tendon that causes decreased tendon tensile force acting on the tendon's osseous insertion points.
    3. Decreased PT tendon tensile force causes decreased magnitudes of STJ supination moment, decreased magnitudes of forefoot adduction moment about the vertical reference axis of the midtarsal joint and decreased magnitudes of forefoot plantarflexion moment about the medial-lateral reference axis of the midtarsal joint.
    4. Decreased forefoot adduction moment and decreased forefoot plantarflexion moment cause increased tensile stress on spring ligament complex.
    5. Spring ligament undergoes plastic deformation, tearing or complete rupture which then causes forefoot to dorsiflex and abduct on the rearfoot.
    6. Forefoot abduction on the rearfoot causes increased medial deviation of the STJ axis (relative to the plantar metatarsal heads) which increases the STJ pronation moments during the latter half of stance phase of gait.
    7. #2-#6 occur again until rotational and translational equilibrium are established at the joint axes of the foot.

    The two axis model was wrong. The longitudinal axis that was taught to me and that was said to be occuring at the midtarsal joint to cause inversion of the metatarsal heads relative to the rearfoot is not the primary cause of this observed motion of the plane of the metatarsal heads to the rearfoot. It is more likely being caused by rotational motions of the navicular-cuneiform joints and cuneiform-metatarsal joints than by rotational motions at the talo-navicular joint. Further research will be necessary to determine how much each joint contributes to this apparent frontal plane motion of the metatarsal heads to the rearfoot during closed kinetic chain STJ pronation and supination.
     
  30. I guess the motion between the navicular and cuboid may be important for terrain adaptation, for independent movement of medial and lateral "columns", which may be linked with peroneus longus function and to allow independent propagation of stress along the medial and lateral columns.

    When we think of variation it is important to remember that some of this is genetic and some is environmental (acquired). For example, the beautiful shape of my nose is partially due to my parents genes and partially due to playing rugby for twenty years. Taking that back to the cuboid, the genotypic shape of the cuboid is fixed at the time of fertilization of the egg, but function, i.e. the environment, may alter the phenotypic shape over time. So when we look at cuboids and say, there is great variation, we cannot be certain how much of this variation is genetic and how much is environmental. P= G + E + (Gx E) + i. Acquired characteristic are unlikely to be passed on to our offspring, but there are some studies which appear to show this. However, these tend to be psycholgical characteristics.
     
  31. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    More on the MTJ

    Three-dimensional in vivo motion of adult hind foot bones.
    J Biomech. 2006;39(4):726-33
     
  32. Here is a quote from the discussion of that article:

    "The rotational motion associated with the navicular and cuboid was similar; the same was true for their translational motions. This supports the claim that these two bones move as a unit."

    This study also supports a uniaxial midtarsal joint axis since these researchers found relatively little motion between the navicular and cuboid in the six adult feet studied.
     
  33. Jeff Root

    Jeff Root Well-Known Member

    If the head of the talus adducs (transverse plane) and plantarflexes (sagittal plane) and the calcaneus everts (frontal plane) during closed chain STJ pronation, then specifically how do the navicular and cuboid move if the cuboid and navicular move as a unit? Please indicate the exact cardinal plane(s) of motion for the navicular and the cuboid with respect to the relative motion of the talus and calcaneus. As Simon indicated, do we therefore consider the talus and calcaneus as a rigid body and if so, why is there a STJ and why do we need STJ motion?

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722

    (877)rootlab
    www.root-lab.com
     
  34. obeywan

    obeywan Welcome New Poster

    How do we apply this to working practice?

    It is Sunday morning and I have just logged on to this discussion. It is interesting to see the development of ideas, and speaking as an osteopath in the UK I wish that osteopaths were as lucid and as willing to share in order to develop both knowledge and profession.
    I have a simple question. How applicable is this to working on real patients? For example there have been arguments that the sacro-iliac joint does not move and yet if it did not move very slightly then we would not be able to walk, viz the restricted joint we treat and the pain that patients feel when the joint locks up. If the navicular and cuboid did not move independently then would we be able to walk as we do? If they do and yet you want to describe their combined movement as that of a single unit, who does this benefit except the researchers?
    Best wishes
    Oliver O'Callaghan-Brown
    Registered Osteopath
    Surrey UK
     
  35. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Oliver - welcome to Podiatry Arena! :)

    Its sometimes called 'academic wankery' - ie academics playing with themselves ;)

    Seriously, on the one hand we have the lab based studies such as the few mentioned in this thread and those others that look at the effects that foot orthoses have on different parameters etc etc

    On the other hand we have various types of outcome studies that show if orthoses work or not (they work).

    What is lacking is studies combining the two --- eg if we can get an adequate model of what happens with the MTJ (or any other segment), then we can get better modelling of the effects that different foot orthoses have in different feet on that MTJ model - once we got that, we need to evaluate the clinical outcomes of foot orthoses that have design parameters designed to alter that model of the MTJ in a predictable way .... then we go back to clinical practice with that data to better prescribe foot orthoses and get better clinical outcomes...God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die
     
  36. Oliver (AKA Obeywan):

    Welcome to Podiatry Arena. It's good to have an osteopath who is brave enough to ask questions in a podiatry forum such as this. By the way, I love your "nickname".

    Let me try to add some clinical relavance to this midtarsal joint discussion for you [and obviously others who are not so daring to ask a question on such a forum]. It just so happens that, currently, midtarsal joint biomechanics is one of my prime academic interests.

    Let me tackle your first set of questions:

    I don't know about the relevance of comparing the sacro-iliac joint to the naviculo-cuboid joint, so let's just look at the pedal joints in question. Here are a few things that we do know about the midtarsal joint:

    1. It does not have two simultaneously occurring axes (i.e. longitudinal and oblique midtarsal joints) as previously described by early authors and taught within the podiatry academic circles for the past 30 years.

    2. It does allow three dimensional (3D) movement of the navicular and cuboid relative to the rearfoot (i.e. talus and calcaneus) both during nonweightbeaing and weightbearing activities.

    3. There is discernable movement between the navicular and cuboid that is probably on the magnitude between 2-7 degrees depending on the individual, the activity occuring, and the internal loads applied within the foot and external loads being applied to the foot.

    4. Studies that have measured the combined movements of the navicular and cuboid together (i.e. as one rigid body), relative to the rearfoot (i.e. as another rigid body) have suggested that it is best to consider the midtarsal joint as having one axis of rotation that is constantly moving in 3D space depending on the phase of gait.

    5. The midtarsal joint should be considered to be a relatively non-constrained joint in that its movement, and therefore its axis location, will be very much dependent on the external loads applied to the foot and the internal resisting forces from the joint surfaces, ligaments and muscle activity of those anatomical structures that are part of or cross the midtarsal joint. In other words, the location of the midtarsal joint axis will be dependent on the loads applied to the foot, so that the motion of the midtarsal joint determines its axis, not the other way around (i.e. the axis determines the motion).

    6. The argument of whether the midtarsal joint is actually better described as one, two, three or four axes is nothing more than a matter of deciding which mechanical model (i.e. 1,2,3 or 4 axis) of the midtarsal joint not only best describes the reality of function of the midtarsal joint but also doesn't complicate its description so much that the intended audience isn't hopelessly confused by its complexity. [For this reason, I think when describing the midtarsal joint to clinicians, the one axis model is in many cases the best way to start teaching midtarsal joint biomechanics since most clinicians do not understand the basic premises of mechanical modelling or of rigid body mechanics.]

    7. Understanding the concept of mechanically modelling the midtarsal joint as being uniaxial does not, in any way, conflict with the fact that there is actual and discernible movement between navicular and cuboid in the live foot during nonweightbearing and weightbearing activities. The two facts can coexist very nicely, as long as one understands the concepts of modelling and rigid body mechanics in much the same way that the calcaneus (which clinicians seem to have no problem understanding about being a "rigid body") is actually elastic and bends a measurable amount as loads are applied to it.

    Now to answer more directly your question: the navicular and cuboid do move and their movements during gait are important to normal gait function but probably much less important than the movements at the ankle joint, subtalar joint, midtarsal joint and metatarsophalangeal joints during weightbearing activities.

    The modelling of two bones as one rigid body is a common modelling technique that has been used for at least 30 years within the international biomechanics community. Even though this modelling technique definitely has limitations, it does allow progress to be made in answering research questions, when the data doesn't allow adequate separation of these two bones into two discrete rigid bodies.

    Good scientific researchers don't like to guess, and should not guess, at things that they can't measure or gather accurate data on. However, guessing at things is a very common practice with clinicians, even though they like to consider that they "know this to be a fact" when instead they are making "educated guesses" based on clinical observations or previous weak research. The history of medicine certainly points to this fact and it is well substantiated in the literature. The bottom line is that, clinicians "think" they know a lot of things, when, in fact, they have little basis of good scientific evidence for this assumed knowledge. I know this very well since I am also primarily a clinician, with a full time and busy practice.

    If the clinician wants to understand the scientific research that is occurring within the international biomechanics community on foot and lower extremity biomechanics, he or she must be able to understand the common language of the biomechanics community. With this understanding of the common language of the biomechanics community, then the clinician will begin to appreciate this research on the midtarsal joint that is currently being done around the world.

    And finally to answer your question more directly, reducing the 3D movements of the navicular and cuboid relative to the calcaneus and talus as occurring around one axis has very signficant benefits for the clinician, as long as they understand the concepts of modelling and rigid body mechanics. By making this modelling approach, the mechanics of the midtarsal joint can be more easily understood by the clinician so that as knowledge grows within the clinician, they can then gain a deeper understanding of the complexities of the midtarsal joint and be ready for more complex biomechanical subjects. It may not make sense initially, but those of us involved in writing on and teaching the subject of midtarsal joint biomechanics think that this type of mechanical model of the midtarsal joint will greatly increase the ability of clinicians to more completely understand both the kinematics and kinetics of the midtarsal joint during nonweightbearing and weightbearing activities.
     
  37. Jeff Root

    Jeff Root Well-Known Member

    I guess I need to answer my own question! The STJ exists in part, because the calcaneus needs to move more in the fronal plane (ie inversion and eversion) than the talus is capable of. The talus can't move as much in the frontal plane as the calcaneus does because it would result in ankle instability. When the calcaneus everts, it also everts the cuboid making the axis of the calcaneocuboid joit more horizontal. When the calcaneus everts and the axis of the CCJ becomes more horizontal, the cuboid can move more in the sagittal plane and when the calcaneus inverts and makes the axis of the CCJ more vertical, the cuboid can more more in the transverse plane.

    When the calcaneus everts with the cuboid, the head of the talus simultaneous adducts and plantarflexes due to internal rotation of the leg during closed chain STJ pronation. Since the head of the talus doesn't evert, there isn't an eversion moment on the navicular. However, as the 1st ray dorsiflexes it also inverts and the navicular inverts as well by rotation about the head of the talus. Simutaneous cuboid eversion and navicular inversion enable the three cuneiforms to splay out thereby contributing to the important adaptive function (ie mobile adaptor) of the foot. The independent inversion of the navicular and relative eversion of the cuboid are an import aspect of foot function that could not exist if the navicular and cuboid acted functionally as a rigid body. Cadivorically it would be easy to fuse the cuboid and navicular to demonstrate this concept since I doubt any of the proponents of modeling the navicular and cuboid as a rigid body would be willing to have it done on them in an attempt to prove their point!

    Some of the critics of the two axis MTJ model don't support its use because it "is false" but are willing to replace it with a false model. Where is the logic in that?

    Respectfully,
    Jeff Root

    Root Laboratory, Inc.
    16739 Placer Hills Rd.
    Meadow Vista, CA 95722

    (877) rootlab
    www.root-lab.com
     
  38. javier

    javier Senior Member

    Just another thought about this subject.

    I have visited an uncommon number of patients showing joint laxity this week, and I was wondering if there is some study comparing foot function on these patients vs "normal" subjects. Or if joint laxity grade was considered when researchers recruited their subjects for the studies that have been named on this thread.

    A decrease or an increase of joint laxity or stiffness would affect both proposed models: rigid body and mobile adaptor. Is it right?
     
  39. Changes in the stiffness of joints in the foot (stiffness being defined as the amount of externally applied force required to move a joint a given distance or arc of degrees) will be regulated by internal forces acting across or in the joint such as, for example, ligamentous tensile force, muscle/tendon force and joint compression force. The rigid body assumption commonly used in biomechanics can be used along with the concept of joint stiffness (as defined above) to make models of the foot that can describe more clearly how the foot reacts to external loading forces such as becoming a mobile adaptor during gait. I have just written a series of four Precision Intricast newsletters using rigid body concept and concept of forefoot dorsiflexion stiffness to discuss the mechanical nature of the midtarsal and midfoot joints (The Load-Deformation Characteristics of the Foot: Volumes I-IV, November 2005 - February 2006, Precision Intricast, Inc., Payson, Arizona).
     
  40. javier

    javier Senior Member

    Interesting subject. Could you share further info with us?

    Thanks,
     
Loading...

Share This Page