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.

First ray mobility during gait by kinematic fluoroscopic imaging

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Feb 11, 2012.

  1. NewsBot

    NewsBot The Admin that posts the news.


    Members do not see these Ads. Sign Up.
    Investigation of first ray mobility during gait by kinematic fluoroscopic imaging - a novel method.
    Martin H, Bahlke U, Dietze A, Zschorlich V, Schmitz KP, Mittlmeier T.
    BMC Musculoskelet Disord. 2012 Feb 9;13(1):14.
  2. Anyone got a full text? Looks like another nail in the coffin of the "hyper-mobile" first ray argument. Of course what this study didn't measure was the dorsiflexion stiffness of the medial column.
  3. Indeed!

    Good to finally see some research that supports my hypothesis that what is clinically called a "hypermobile first ray" is actually a first ray with decreased dorsiflexion stiffness. A "hypermobile first ray" actually doesn't move more during gait but rather exerts less force on the ground for the dorsiflexion movement it does undergo when compared to a "normal first ray". This is another reason why we should get rid of the term "hypermobile" since the term "stiffness" is scientifically appropriate and necessary to describe this force vs motion biomechanical function of the first ray, not the term "mobility" or "hypermobility" or "hypomobility".

    Here is what I wrote about this subject in my February 2005 Precision Intricast Newsletter on the subject: "Hypermobility of the First Ray - Volume II" (Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009, pp. 77-78).

  4. Here are the drawings from my February 2005 Precision Intricast Newsletter (Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009, pp. 77-78), where I use a pine board as being analagous to the first ray with reduced dorsiflexion stiffness and oak boards as being analogous to metatarsal rays of normal stiffness. A steel plate resting on the end of the boards is meant to be analagous to the flat contour of the ground that the metatarsal heads all rest upon and the 100 pound boy walking from one side of the boards to the other is analagous to the movements of the center of pressure under the metatarsal heads during weightbearing activities. I first used these images as a mechanical analogy of why the term "hypermobility" of the first ray is improper and ambiguous and should be replaced by the term "decreased first ray dorsiflexion stiffness" during the lecture, "Understanding the Mechanics of the First Ray: Hypermobility vs. Decreased Dorsiflexion Stiffness", that I gave on November 4, 2005 at the 8th Annual International PFOLA Conference on Foot Biomechanics and Orthotic Therapy in Vancouver.
  5. Very good. All we need to do now is get him talking like that to a live audience, on a stage, in a conference hall.... In Florida, Ray Anthony asked me who the new kids on the block were... I told him: Ian Griffiths. I firmly believe that.

    But then he's had good examples to follow...

    Edit: that's now completely out of context because some posts have been deleted ;-)

    Attached Files:

  6. Back to the plot....... that study doesn't really prove nor disprove any hypotheses regarding first ray stiffness, since it only looked at motion and did not measure stiffness. The first ray stiffness might have been the same in both groups too. Their description of the clinical method they employed in determining first ray hypermobility was somewhat vague, certainly they did not measure stiffness in a quantitative sense. So..... lets not get too excited; all that it showed was that there was no significant difference in motion between groups defined by two clinicians as being "hypermobile" or not.
  7. I guess we will need to wait another seven years for that study to come along.:rolleyes:
  8. I guess. But in the mean time, lets not extrapolate beyond the available data and rather, maintain a scientific approach. Otherwise we start to sound like E.G., D.S. and all. Your hypotheses are good Kevin, but they remain as hypotheses until such time that they are tested scientifically. I reckon someone could get this study done and published in less than seven years, Kevin.:drinks
  9. Simon:

    First of all, isn't the "drawer test" used by the two clinicians that separated the test subjects into two groups a test of joint stiffness? Just because researchers call their measurement of first ray dorsiflexion motion "first ray mobility", it is still a measure of first ray dorsiflexion stiffness (or compliance) if the load applied is constant from one subject to another.

    Secondly, give me a good mechanical reason why a subject with a first ray with decreased dorsiflexion stiffness would show increased first ray dorsiflexion compared to a subject with normal first ray dorsiflexion stiffness during walking.

    How are using the mechanical concepts of first ray stiffness during walking any different than the mechanical concepts of leg stiffness during running? Stiffness is simply a measure of deformation for a given loading force. Therefore, we should be able to make very reasonable and mechanically valid predictions about the forces acting on and within the foot and lower extremity during these activities by using the mechanically-accepted concept of joint stiffness. Wouldn't you agree?
  10. Yes but the description is somewhat vague, we have no test- retest reliability data and we have no quantification of load/ deformation. So, my scientific head says.. hmmmm. Prove to me that the load was constant.
    O.K. several points here; firstly define "normal" dorsiflexion stiffness- something else we have no normative data for; secondly, and I'm not sure what you said is what you wanted to say, but given the same loading a subject with decreased dorsiflexion stiffness should show greater dorsiflexion under the same loading as an individual with greater dorsiflexion stiffness under the same loading. However, two individuals with the same dorsiflexion stiffness should show different deformation (motion) if the loading on the two were not the same. Thats the key, we have no idea of the loading forces on the medial colums in this study- hence we have no idea of the stiffness. I'm guessing they weren't all the same weight. So, answering your question- decreased dorsiflexion stiffness = more dorsiflexion for a given dorsiflexory force. But the same dorsiflexion might occur in 1st rays with different stiffness if the dorsiflexory force is variable. And since dorsiflexory force was not measured.... we have no idea. Which takes us back to our recent discussion on contact times and leg stiffness, without a knowledge of the applied force, contact times are pretty useless; the same argument applies here.

    See above.:drinks Viz. if we don't know what the applied force was (and we don't) and we look at deformation in isolation(which this study did), we have no idea of the stiffness. And in the paper in question- we have no idea what the stiffness was since all we have is the deformation data and no idea of the applied force. Hope this helps, Kevin.

    Two springs deform the same amount but under different loads, which spring is stiffer? The one with the higher load upon it. Which feet in this study had the higher loads on their medial columns? What do the hypotheses suggest? That'll be the pathologic feet having higher loads medial due to the "rearfoot' pronation placing "greater body weight medially" and therefore greater stiffness of the medial columns in the pathology group when compared to the control group, but now I am hypothesising... And it is Saturday night.
  11. If you had five springs in a row, four with a higher stiffness and one with a lower stiffness, and you placed all of the springs under compression of the same magnitude, which spring would exert the lowest force? Answer? The spring with the lowest stiffness.

    My point is, by definition, stiffness is a measure of force needed to deform a spring a given amount. Therefore, for a series of adjacent springs all deformed by a flat surface that determines the magnitude of deformation of each spring, then, by definition, a spring with lower stiffness will still be deforming the same amount as a spring of higher stiffness. However, the spring with a lower stiffness will be exerting decreased force on that flat surface that deforms that series of adjacent springs and the springs with higher stiffness will be exerting increased force on that flat surface.

    In other words, I don't believe that this concept needs to be tested experimentally in order to be be proven that it will be true, no more than we need to test the concept that a ball will drop and accelerate toward the ground when released from a height here on our planet. In fact, I believe this concept can likely be proven mathematically using known physics concepts since the definition of spring stiffness relies on force and deformation so that, by definition, we should be able to mathematically calculate the force exerted by the spring given the magnitude of its deformation.

    The problem I see, then, is not that a low stiffness metatarsal will deform the same amount as a high stiffness metatarsal when deformed by a flat surface like the ground, since, by definition, this should be a given. The problem, rather, is that most podiatrists are assuming that the terms "mobility" and "hypermobility" describing first ray load-deformation characteristics are accurate terms that means that the first ray will dorsiflex too much under weightbearing conditions, when, in fact, the problem is not that the metatarsal ray dorsiflexes too much, but that it exerts too little force when it is deformed a given magnitude in a dorsiflexion direction.
  12. And my point is: where in this study did they measure loading? Hence while the hypotheses may be good, they are not validated by this study, Kevin.

    Let us list the potential reasons for the no significant differences observed in this study......

    So your statement:
    Is in no way supported (nor refuted) by this study. But that's science for ya'.
  13. admin

    admin Administrator Staff Member

    copyright issues....
  14. Craig:

    The pdf is freely available on their website. How is this a copyright issue?
  15. admin

    admin Administrator Staff Member

    Because there is advertising on their site they want you to see when you download it from their site. Even though its freely available, its still subject to copyright.

Share This Page