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.

One Axis Midtarsal Joint Model

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Daniel Bagnall, Aug 7, 2011.

  1. Daniel Bagnall

    Daniel Bagnall Active Member


    Members do not see these Ads. Sign Up.
    Hi there

    I'm currently reviewing Midtarsal Joint (MTJ) function and I am trying to get my head around the one axis model. From the reading I've done thus far, and from what I understand currently, it is proposed that the cuboid and navicular can be modeled as a rigid body. As a result, there can only be one axis of rotation at any given instant of time. Furthermore, three MTJ reference axis have also been described. These consist of the z-axis, x-axis and y-axis.

    Therefore, am I correct in assuming that the MTJ axis could be relating to either the z-axis, x-axis or y-axis at any given moment in time?

    Or, is there a predominant mean axis of rotation (similar to the spatial location of the STJ axis) at the MTJ based on the collective motions which determine these reference axes I've outlined that occur during the different phases of the gait cycle?

    Am I on the right track here?

    I'd greatly appreciate it if someone who has greater knowledge and expertise in this area can assist me in my understanding.

    Kind Regards

    Daniel Bagnall
     
    Last edited: Aug 7, 2011
  2. joejared

    joejared Active Member

    First, assuming certain things about the x,y,z and terms for rotation about a respective axis.

    Left and rule assumed.
    x=lateral to medial axis (pitch)
    y=proximal to distal axis (Yaw)
    z= vertical axis (Roll)


    From pronation to supination, you could assume yaw to be the primary rotation but in effect, it also rolls (twists) because the rotation about Y will pull one side of the midtarsal joints proximal as the opposite side is pushed distally. I am by no means a doctor, but would say that a single axis alone wouldn't completely define motion of the midtarsal joints, simply because of the interaction of the bones adjacent to the joints.
     
  3. Craig Payne

    Craig Payne Moderator

    Articles:
    7
    There is some confusion between a joints axis (or axes) of motion that a joint moves about and the xyz reference axes/planes that motion can be described as being relative to.
     
  4. Admin2

    Admin2 Administrator Staff Member

  5. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Craig

    This is precisely why I'm confused. Why are these reference planes also referred to as axes? Are reference planes and axes used interchangeably? If motions are occurring in each of these references planes, then wouldn't that also mean that they each have a theoretical axis of rotation? Therefore, I'm trying to ascertain if there is an actual single axis that is being referred to in the literature or is the single axis dependant on the motion that's occurring at a specific instant in time which could correlate to either the z, y or x axis? Or in other words, at any given moment in time during the gait cycle the MTJ axis is considered to be either the z,y or x axis. Do you see where I'm going with this?

    To try an illustrate my point, lets look at forefoot dorsiflexion/plantarflexion motions compared to inversion/eversion motions. Based on my current understanding, these motions individually would determine theoretical axes of rotations. As a result, why cant I get my head around there being one predominant axis when it seems to me that the axis is dependant on the motion thats occurring at any given time which could be considered to be either the z,y or axis.

    Regards

    Daniel Bagnall
     
  6. Daniel Bagnall

    Daniel Bagnall Active Member

    In addition to what I've tried to explain above:

    I think I am also getting confused when I'm trying to correlate Nester et al's work to rotational equilibrium at the MTJ. When observing rotational equilibrium at the MTJ, would I be correct in assuming that we are mainly taking into consideration forefoot dorsiflexion and rearfoot plantarfelxion moments which therefore determine the medial and lateral axis/reference plane? As a result, how does the mean axis Nester et al propose i.e. 29 degrees from sagittal plane and 38 degrees transverse plane, correlate to rotational equilibrium at the medial and lateral axis? They seem to me like two completely different axis.

    Regards

    Daniel
     
  7. Daniel,

    There are several ways we can analyse the motion occurring at the midfoot. I think you are getting confused because you are attempting to mix two different methods. One way to look at the motion is to treat the cuboid and navicular as a rigid body and analyse the motion to derive a series of axial positions, another way is to analyse the motion occurring in each plane about axes which are normal to these planes. Both are artificial constructs- axes don't really exist.

    I've never been a big fan of the rigid body approximation of the cuboid-navicular as I've always believed that motion occurs between these two bones. This is borne out by the data which demonstrates that motion between these bones is significant: http://www.jfootankleres.com/content/2/1/18
     
  8. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Simon

    So when looking at rotational equilibrium at the MTJ which theoretical axis best applies to this theory? I would think, the reference axes best explains how rotational equilibrium can be achieved at the MTJ. Most of the explanations I've read though seem to predominantly focus on the medial-lateral axis but not so much with regards to other axes.

    I haven't read the link you posted yet. If motion does occur between the cuboid and navicular what implication would this have on the one axis model? Would this also affect how equilibrium is currently perceived at the MTJ?

    I still haven't grasped this fully yet hence why I'm asking quite a lot of questions.

    Thanks

    Daniel
     
  9. You can model it either way, either using the reference plane axes or the instantaneous centre of rotation, just don't try to mix and match. If you read the MTJ rotational equilibrium thread, we did both, but not at the same time.

    The implications of significant movement between the cuboid and navicular are that a model which assumes a rigid body approximation is necessarily an over-simplification of reality. That is not to say you cannot use this model, rather that you should understand its short-comings. In reality, there will be an instant centre of rotation at the calcaneo-cuboid joint, another at the talonavicular joint, another at the navicular-cuboid joint etc etc. for all of the articulations within the midfoot.

    But we can still think in terms of a "single" net instantaneous axis to define midfoot motion- it's all about scale. If we look at the foot as a whole and move the forefoot on the rearfoot, we can say that the movement is occurring around a single net axis. Or we can say that the net movement is a composite of movements occurring about 3 axes which are normal (perpendicular) to the reference planes- two different models to explain the same observation. But if we want to look at the individual bones, then we really need to define their movements about several instantaneous axes- a different model again. Ultimately, it depends on the question you are trying to answer as to which model works best.
     
  10. Hi Simon
    Just wanted to say thanks for the link to the article which i found to be great read with coffee and cherios this morning.
    Ive been graduated for 2 yrs from university where i was taught that certain foot types display certain traits and deviations from the norm were not the ideal.
    After working in the nhs for the last 18 months and having an interest in the mechanical side of podiatry i have accepted that the terms "normal" or "ideal" in relation to foot function dont really mean anything.

    Hence why I loved reading this article
    thanks :)
     
  11. Daniel Bagnall

    Daniel Bagnall Active Member

    Simon:

    Thank you for the article. I found it to be a very interesting and informative read.

    I’m trying to figure out which model is most relevant in a clinical setting and from an orthotic px perspective. The model that seems to make the most clinical sense, when assessing MTJ function, would be to assess MTJ range of motion/stiffness as per the reference axes. Specifically this would consist of assessing MTJ stiffness in terms of assessing plantarflexion/dorsiflexion, abduction/adduction and inversion/eversion range of motion.

    When you speak of an instantaneous axis, are you saying this occurs when all these motions are occurring simultaneously? For example, in open kinetic chain, when the rearfoot is grasped and the forefoot is moved passively, can we therefore assume that this collective movement is rotating about a “single” axis?

    Regards

    Daniel
     
  12. Pretty much. Its the resultant net axis if you like. In reality, there a several instantaneous axes all occurring simultaneously at each of the joints undergoing motion. But for the sake of simplistic modelling we can say the single resultant axis is the net of all these axes put together. Its a simplified model though, and you've got to remember that.

    When you perform the examination you describe you are generating a single net axis which is perpendicular to the plane of interest. So with inversion/ eversion you generate a single axis which is perpendicular to the frontal plane and so on. So what you are determining is the movement envelope in each plane. Whether or not this movement envelope is available during dynamic weightbearing function is another question again.
     
  13. efuller

    efuller MVP

    I agree with pretty much everything Simon said, but I thought I'd say the same thing a little differently. I hope this helps.

    Axes are imaginary lines we use for different things. The reference axes are just that. They are axes that we use to orient ourselves relative to a single point. You will often her about a laboratory axis and this is used describe motion relative to the room or the ground. You can also have a reference axis in one body part. When the reference axis is in one body part you can describe motion relative to that body part. You will use different reference axes when you have different goals in describing motion.

    An instant center of rotation is an imaginary line that describes the rotation of one body relative to another at two different points in time. This axis then is helpful in describing the motion that occurred between those two bodies. It may or may not describe all the motion that occurred between those to points in time. For example, you can grab a rear foot and hold it steady and then grab a forefoot and plantar flex and dorsiflex the forefoot on the rearfoot without abdcuting oar adducting the forefoot. This would give you a horizontal axis of rotation for this particular motion. Now, you could, from the same starting position as the first example, adduct the forefoot, then abduct the forefoot without plantar flexing it to return it to the same position. This is point in time #2. Then you could plantar flex the forefoot on the rearfoot between time #2 and time #3. So, between time one and time 2 there is a vertical axis of rotation and between times 2 and 3 there was a horizontal axis of rotation. And if you look at the relative change between times 1 and 3 you would have a horizontal axis of rotation. This is because an instant axis of rotation can only be calculated between two points in time.

    So, to answer your question, if you define the rearfoot as a rigid body and the forefoot as another rigid body, when you move them you can say that they have a single axis of rotation for that movement. However, other motions may occur. Motion does not have to occur about that axis of rotation. It's not like a hinge where the structure of the hinge constrains the motion. It's good to look at the anatomy of the joints to understand the constraints to motion.

    Eric

    Eric
     
  14. Daniel Bagnall

    Daniel Bagnall Active Member

    Simon and Eric:

    Thank you for your detailed explanations and helping me understand this concept better.

    Regards

    Daniel
     
    Last edited: Aug 7, 2011
  15. Daniel:

    I wrote a series of five newsletters, from August 2001 to December 2001 (10 years ago!) on the one axis versus two axis midtarsal joint axis question, that were all eventually published in my second book (Kirby KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 65-78). I think you will find these newsletters interesting and helpful.

    As Simon and Eric have already nicely pointed out, when we are discussing the motion of the midtarsal joint, we are actually discussing a motions of a set of four bones (i.e. calceneus, talus, navicular and cuboid) that are all rotating and translating in space relative to each other during weightbearing and nonweightbearing activities. To simplify the motions of the navicular and cuboid relative to the rearfoot (i.e. calcaneus and talus), researchers may often assume that the navicular and cuboid can be modelled as a "rigid body" with very little motion between them, even though we know from recent bone pin research that here is some motion between these two bones during weightbearing activities.

    Chris Nester's "reference axes" of the midtarsal joint (MTJ) is something that Chris and I actually talked and agreed upon a couple of years before he published his papers on the subject. He had made the brilliant observation, to paraphrase, "motion determines the axis, the axis doesn't determine the motion" in one of his papers. What this means is that, in any joint of the body, the actual axes of motion that occur are not so constrained that they will always occur along the same spatial location relative to the bones of the joint. Some pedal joints are more constrained than other pedal joints.

    For example, the subtalar joint (STJ) axis is a fairly tightly constrained pedal joint since the talus and calcaneus have very tight interosseous ligaments within the tarsal canal that restricts the instantaneous axes of motion to a fairly tight "bundle" of STJ axes that move relatively little relative to the calcaneus and talus. On the other hand, the MTJ has much less constraint than does the STJ so that the MTJ axis may swing widely in space depending on how the external forces and internal forces are acting across the MTJ at any instant in gait. The lessened constraint in the MTJ, especially during non-weightbearing function, is likely due to the looser ligamentous connections between the rearfoot and navicular/cuboid.

    Since the MTJ is so loosely constrained, and since its axis of motion may swing widely during gait first from one spatial location and then to another spatial location in milliseconds, the reference axes of the MTJ are an attempt by us to be able to accurately describe the motion of the MTJ by assigning their motion to a dorsiflexion-plantarflexion direction (medial-lateral MTJ axis), a adduction-abduction direction (vertical MTJ axis) and to a, inversion-eversion direction (anterior-posterior MTJ axis). In other words, if the MTJ has a triplanar motion, [which it likely has for 99.9% of the time], then a certain percentage of the MTJ motion will occur at the anterior-posterior MTJ axis, a certain percentage of the MTJ motion will occur at the vertical MTJ axis and a certain percentage of the MTJ motion will occur at the medial-lateral MTJ axis.

    Here is the text from the lecture I gave on this same subject at the PFOLA meeting from 2006 that is based on my five Precision Intricast newsletters in my book. Hope this helps.

     
  16. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Kevin

    I greatly appreciate your contribution and feed back to this thread. Thank you for providing your lecture notes.

    When I’m treating biomechanical related lower limb pathologies I’ve found your research regarding Subtalar Joint Axis Mechanics and Rotational Equilibrium Theory extremely beneficial. It has been beneficial in a sense that I’ve had a lot more success in obtaining the desired therapeutic outcomes with patients.

    I’m now trying to figure out how the STJ axis location and the MTJ axis relate to one another in terms of assessment and orthotic prescription. Kevin, how to you go about assessing the MTJ in clinical practice? When assessing MTJ range of motion, do you qualitatively measure in terms stiffness? And how to you conclude what has increased/decreased stiffness?

    Due to the STJ axis being tightly constrained I find this concept a lot easier to grasp and how this can assist with orthotic prescription variables. As the MTJ is loosely constrained and there is quite a bit more variability in the spatial location of the axis, I don’t quite understand how to apply this in regards to orthotic prescription variables. How does the MTJ axis determine what variables you think are necessary in an orthotic prescription?

    Kind Regards

    Daniel
     
  17. Daniel:

    That is a good set of questions.

    In the non-weightbearing exam, I will see how much the medial and lateral forefoot will dorsiflex relative to the rearfoot for a given manual plantar load. I take mental notes of this "stiffness", but don't measure it quantitatively. However, the most important observation I make during my exam is how the forefoot moves on the rearfoot during weightbearing (i.e. standing, walking and/or running) so I can see if the changes in MTJ position during weightbearing activities seem excessive or not.

    I feel that the most important part about the material I presented in my lecture from five years ago is the concept of rotational equilibrium of the midtarsal joint. In other words, the concept of rotational equilibrium about the MTJ axis is where we can predict with the certainty of Newtonian mechanics that when we see MTJ stability or motion with the foot being subjected to external loading conditions, we know that there must be some internal forces acting across the MTJ that are resisting the external forces tending to make the MTJ stable or the longitudinal arch flatten and/or forefoot abduct/adduct and/or forefoot invert/evert. This is critical to understanding how mechanical treatments such as foot orthoses, shoes, braces and foot/ankle strapping can produce their profound therapeutic effects.

    I don't worry about the MTJ axis since the MTJ axis will tend to move into a new spatial location which will be dependent on the magnitude, direction and point of application of the external forces and internal forces pulling and pushing on the forefoot relative to the rearfoot at any instant in time. I suggest worrying more about abnormal motion of the forefoot on the rearfoot, understanding that this is caused by a external force-internal force mismatch that our treatment might be customized to address.

    I have added a video of my daughter-in-law's foot that I shot for this lecture on the MTJ. Note that I can apply an input force onto the forefoot in many directions to cause a MTJ axis to change over widely varying spatial locations. Did the "MTJ axis" of this foot have much affect on the motion produced? No, because in a loosely constrained joint such as the MTJ, the motion determines the axis and this can lead to widely varying spatial locations of the MTJ with a wide range of external input forces onto the forefoot.

    Hope this helps.


     
    Last edited by a moderator: Sep 22, 2016
  18. Daniel Bagnall

    Daniel Bagnall Active Member

    Kevin:

    Your response and everyone else's input has helped immensely. Thanks again for your all of your help.

    Regards

    Daniel
     
  19. Shalom

    Shalom Active Member

    However this theory fails to understand that where significant restriction exists in the MTJ i.e due to trauma, arthropathy and long-term osseous restriction, significant consideration needs to be given to the motion of the MTJ when prescribing orthoses. Despite the STJ neutral theory and rotational equilibrium, Newtonian does not postulate the differences in a given force that opposes movement where there exists significant disparities in force generated, and the structural components of this force.
     
  20. What the .......???!!!:confused:
     
  21. Shalom

    Shalom Active Member

    Exactly my thoughts also.
    Not convincing thought coming from a man who claims that he understands foot mechanics like the lines on the back of his hand. You dissapoint me.

    Restrictions in the MTJ complex, will alter the kinetics and kinematics of an individuals walking. Where you state that 'I don't worry about the MTJ axis since the MTJ axis will tend to move into a new spatial location which will be dependent on the magnitude, direction and point of application of the external forces and internal forces pulling and pushing on the forefoot relative to the rearfoot at any instant in time. I suggest worrying more about abnormal motion of the forefoot on the rearfoot, understanding that this is caused by a external force-internal force mismatch that our treatment might be customized to address.'

    You are neglecting the fact that where there is osseous restriction in the MTJ, its axial movement should be taken into account when prescribing orthoses as it will not just 'move into a new spatial location' as it is unable to do so, then you have an abnormal forefoot motion when compared to the rearfoot, however you cannot purely take Newton's laws of physics and say 'to every force there is an opposing counter-force when clearly there is a force mis-match'. So then going from a force abnormality is it not also possible that there is an axis-miss match? Ie - MTJ Axis does not allow sufficient movement as the STJ axis.

    What do you propose?
     
  22. "Shalom":

    What do I propose? I propose that you first tell me your real name before I take time out of my busy day to attempt to respond to your rambling and nearly incoherent statements. That is what I propose.
     
  23. efuller

    efuller MVP

    The axis is an imaginary line that describes the motion that we see. The motion can determine the axis. The axis cannot determine the motion. The MTJ is essentially a planr joint with an infinite number of potential axes of motion. However, it will have only one at any instant in time.

    Eric
     
  24. Shalom

    Shalom Active Member

    Who? Who is but the form following the function of what and what I am is a man in a mask.
     
Loading...

Share This Page