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Osseous locking mechanism

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Ak_39, Dec 2, 2011.

  1. Ak_39

    Ak_39 Welcome New Poster


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    Hello everyone, I was wondering about the osseous locking mechanism (more like worrying about my lack of understanding), if the forefoot is locked at the midtarsal joint does that mean the subtalar joint is supernated, neutral or pronated? someone please help
     
  2. Ak_39

    Ak_39 Welcome New Poster

    Hello everyone, I was wondering about the osseous locking mechanism (more like worrying about my lack of understanding), if the forefoot is locked at the midtarsal joint does that mean the subtalar joint is supernated, neutral or pronated? someone please help
     
  3. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    The osseous locking mechanism is a bit of a furphy.
    There are variations in stiffness of the MTJ with variations in the position of the STJ
    Suggest you read some of the MTJ threads: Midtarsal Joint
     
  4. efuller

    efuller MVP

    The osseus locking mechanism was dreamed up by someone sitting in a arm chair. There is no research behind the idea. A better way to understand the midtarsal joint is to look at the articulations of the bones and the ligaments around the joints. That will help you understand what limits motion at the midtarsal joint.

    There is a decrease in range of motion of the midtarsal joint when the STJ is supinated, but that has more to do with the relative position of the anterior facet of the calcaneus and the anterior facet of the talus. It's not about the axes of the anterior facets of those joints either. See Van Langalaan 1983. In that paper there is a literature review that destorys the old idea of what caused "locking of the MTJ". I believe a pdf of that thesis was posted in the biomechanics section of podiatry aena recently.

    Who told you that the osseus locking mechanism exists?

    Eric
     
  5. RobinP

    RobinP Well-Known Member

    It amazes me that podiatry schools/universities still teach this drivel. Surely they should be the most current people?
     
  6. Alex Adam

    Alex Adam Active Member

    H. Hlavac described the principle of locking of the foot during weight bearing, a good understanding of osseous and soft tissue restraining mechanism is important( Root et al) together with propriocetive resonse activation.
    Locking can only occur at a specific moment when all structures are in the correct alignment at mid stance any movement beyond this will automatically result in another section becoming unlocked and thus produce extraneous motion.
     
  7. Griff

    Griff Moderator

    Joints do not 'lock' and 'unlock'
     
  8. admin

    admin Administrator Staff Member

    Threads merged
     
  9. efuller

    efuller MVP

    I believe that Root and Weed also talked about locking of joints. That doesn't mean that they were right and this phenomenon exists. When you look a their citations, they usually attribute this locking idea to Elftman. The van Langaalan paper clearly showed that Elftman misquoted Manter when he made this assertion. Elftman claimed it was the allignment of the axes of the joint that allowed the locking. The axes of a joint are imaginary lines and imaginary lines cannot limit motion.

    This is treating the foot as a theoretical black box with a theoretical locking mechanism. Try inserting specific bones and ligaments into the above sentence and then provide evidence that the movement of one anatomical structure "unlocks" the other anatomical structures.

    Eric
     
  10. David Wedemeyer

    David Wedemeyer Well-Known Member

    Eric I'm surprised at you. Everyone knows who discovered the concept, at least with refeence to the STJ:

    http://www.mlrs.info/staff.htm

    "Dr. Glaser in his research also discovered the locking mechanism of the subtalar joint and function of the talo-cuboid joint."

    (among his other stunning academic achievements) :rolleyes:
     
  11. Yes, David, Ed Glaser is a legend in his own mind.;)
     
  12. efuller

    efuller MVP

    And I thought you were making up talo-cuboid. It's really on his blurb on that website.

    Eric
     
  13. David Wedemeyer

    David Wedemeyer Well-Known Member

    You just cannot make this stuff up Eric. With the advent of the internet cowpies of all dimension (and odor) can be propagated in continuing education courses near you!! :D
     
  14. Alex:

    As Ian noted, the joints of the foot do not "lock" or "unlock". In fact, if you could provide me a definition of what "foot joint locking" means, then that would at least give us a basis for something to discuss. I try to never use the term "lock" or "locking" or "locked" when referring to any joints of the foot and lower extremity since this terminology is not biomechanically accurate.

    All of the joints of the foot and lower extremity will rotate and translate further with increasing magnitudes of external and internal loading forces acting across them. Therefore, by definition, they do not "lock" or become "locked" or have "locking mechanisms".

    For example, many clinicians will examine the foot, put a manual loading force of 10 lbs on the plantar aspect of the 4th and 5th metatarsal heads and declare "the midtarsal joint is now locked!". However, when this same foot runs or jumps and now the 4th and 5th metatarsal heads are loaded plantarly by a 50 lb ground reaction force, do you think the midtarsal joint will rotate and translate only the amount seen when only 10 lbs of force are applied? I hope not.

    If the midtarsal joint truly "locked" then it would not have any spring-like function and would not be able to absorb the loads from weightbearing activities that it certainly does quite well. The foot is a variable-stiffness spring, not a locking ratcheting mechanism as the term "locking" implies.

    Even though this concept was not clearly understood by the originators of podiatric biomechanics that you mention in your posts, there is no doubt that understanding the foot as being a variable-stiffness spring is the way forward for future podiatric biomechanists.
     
  15. CraigT

    CraigT Well-Known Member

    Kevin- excellent one line summary!
    Is there a study which quantifies the range of stiffness within and between subjects' feet??
     
  16. Craig:

    No such study has been done but it certainly is research which could be very helpful in understanding the load-deformation characteristics of feet....a topic which is one of the keys to understanding foot and lower extremity biomechancis.

    To start out your reading, here is a study that represents some ideas as to how we may progress forward on this subject.

    Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RMcN: The spring in the arch of the human foot. Nature, 325: 147-149, 1987.
     

    Attached Files:

  17. Rob Kidd

    Rob Kidd Well-Known Member

    I have read withg interest this debate - and have comments to make. But first, I agree with all the above, except please do not throw Elftman out with the bath water. Yes I recognise that his "axes" were decidedly simplistic - I have always used the words "bisection lines" to avoid any confusion with joint axes per se. However, first it is important I feel to look at the "midtarsal restraining mechanism" as defined by Elftman and his followers, in humans, and then in apes - who lack a talar head torsion angle (see Pete Lisowski's work, 1967). Then one can see that the talar head torsion that we have - as a peramorphic heterochrony of our hominoid past - lends us a restraining mechanism as defined by Elftman. The mistake, as I see it, is to attempt to give a "degree-by-degree" value to it. That is, one should simply accept that the subtalar pronated position gives one a greater M/T ROM and a subtalar supinated position gives one a lesser ROM. Thus, as a working principle, and with no degree values in mind, it is a useful clinical tool. We seem to make mistakes of trying to extrapolate scientific fact from clinically useful findings; it does not devalue them - it simply does not validate them in scientific terms, and certainly does not erode their value clinically.

    As a matter of interest, Mike Bennett, in the paper noted above, is an ex pat UK (like myself), ex of Leeds, and has been in Brisbane for perhaps 22 years. He was at one time a key member of the Australasian Society for Human Biology - our paths crossed at our annual conference in Perth in 1990.
    Rob
     
  18. Rob:

    I believe that the point to be made about the concepts proposed by Elftman (Elftman H: The transverse tarsal joint and its control. Clin. Orthop., 16:41-44, 1960) was that he felt that both the talo-navicular joint and calcaneo-cuboid joint each had separate "axes". In fact, he proposed that both the CCJ and TNJ have two separate joint axes, designated CC-1 and CC-2 for the CCJ and TN-1 and TN-2 for the TNJ. However, he never described how he came up with these "axes" or the number of feet used to "determine" these "axes". It appears, instead, that Eltman was using only his imagination and his detailed observation of joint shapes in order to come up with the idea that both the TNJ and CCJ both have two "axes". Unfortunately, Elftman's ideas, subsequently, were misinterpreted by many authors following him to come up with this idea that a "crossing of axes" somehow limited midtarsal joint motion when the foot was supinated.

    With the perspective of history giving us greater clarity, we should be able to see that this is yet another example of how improper and mechanically illogical biomechanics concepts are passed on from one generation of clinicians to another until someone comes up with a more accurate representation of biomechanical reality. The "crossing of axes" does not limit motion at the midtarsal joint....never has....and never will.
     
  19. efuller

    efuller MVP

    I haven't read the Elftman paper in over 15 years. I'm having trouble recalling what exactly he said the restraining mechanism was. I have looked at cadaver specimens where I cut the navicular free from the talus and turned the navicular perpendicular to its normal allignment and noted that curvatures don't match in that direction. However, before cutting the navicular out, there was plenty of inversion-eversion range of motion available of the navicular relative to the talus. The range of motion appeared to be limited by the ligaments around the joint and not the lack of congruence of the joint surfaces.

    The calcaneo cuboid joint is an entirely different beast. This joint is quite variable across people. So, "eye of the conesieur" (his actual wording) determinations would be even more suspect than usual. Huson also wrote about the ligamentous restraining mechanisms especially the long and short plantar ligaments and how they helped determine the motion of the joint. I think the joint is best understood as a planar joint where the joint surfaces and bony shape can sometimes help limit motion. Mostly motion is limited by ligamentous tension.

    Eric
     
  20. Rob Kidd

    Rob Kidd Well-Known Member

    I am sure you are all correct. All I am saying, is from a clinical view point (not scientific per se) the concept of a M/T restraining mechanism in which the position of the S/T jt does, at least to some extent, govern the ROM at the M/T jt (so many abbreviations!) is useful, if only to try to explain to patients why they are exessively mobile. I have long argued not to mix science and clinical accumen - they may embrace, they may not. However, noted by many (including myself)is that the increase in talar head torsion angle would tend to decrease the ROM at the MT Jt. All apes have a head torsion angle of about 20-25'; ours is about 40'. If memory is correct, try the work of Eric Trinkaus - on Neandertal feet. And as for the CC jt itself; evidence from the fossil record would tend to suggest a late development of the process calcaneus - which when one cuts to the quick is about lessening the ROM at the CC jt. It was present in East Africa at 1.7MA (OH8 - Homo habilis); it was not present in South Africa in Australopithecus sediba (1.9MA). That could easily be explained away in terms of local effects, dating issues etc. However, all evidence (from a pathetically small sample) suggests a late change to a rigid Mt jt - as against the mobile "early heel lift" chimp-like mt jt.
    I have started blathering, so I will stop - my hobby horse! Rob
     
  21. efuller

    efuller MVP

    I have a problem using the decrease in range of motion of the MTJ in response to STJ position changes to explain flexible feet. There is a wide range of flexibility in the MTJ. The most flexible foot can, in its maximally supinated position, have a greater range of motion than the most rigid foot in its maximally pronated position of the STJ. More below

    There was a paper from the early 1900's that stated that the calcaneo cuboid joint was one of the most variable joints of the body. Sometimes, the anterior portion of the calcaneus has a bony protuberance that hangs over the cuboid. (From lateral view there is an "s" shape to the cc joint.) This protuberance may limit dorsiflexion of the cuboid on the calcaneus. Other times the anterior surface of the calcaneus is flat. With a flat joint there is no bony block to motion and only the ligaments can limit motion.

    Two points. Since the joint is so variable it would be dangerous to make comparisons to the past with very few samples.

    The rigidity of the MTJ may have more to do with the shape of the CC joint than any positional change in the STJ. The STJ is rarely more than a couple of degrees from maximal pronation in static stance. It is unlikely for the STJ to have much effect on the rigidity of the MTJ becuase the STJ doesn't move that much during the stance phase of gait.
     
  22. CraigT

    CraigT Well-Known Member

    I like this discussion.
    What about if Rob changed his statement to...
    "the concept of a M/T restraining mechanism in which the position of the S/T jt does, at least to some extent, govern the ROM at the M/T jt (so many abbreviations!) is useful, if only to try to explain to patients why and how they are functioning in a relatively mobile position."

    I know this is a recurring theme in my discussion with patients when explaining what I am observing with respect to their mechanics. This is not an issue of whether the individual has mobile feet or not. I would suggest that this mechanism is present in almost all feet, just that the total ROM and change in stiffness varies.
     
  23. Rob Kidd

    Rob Kidd Well-Known Member

    I am fine with that! My point was entirely clinical, and had no scientific basis. From that view point I stil believe it to be a useful explanatory tool for patient explanations.
     
  24. There is no doubt that subtalar joint (STJ) rotational position does affect the dorsiflexion stiffness at the midtarsal joint (MTJ). Pronation of the STJ will bring the talo-navicular joint (TNJ) into a relatively more plantar position to the calcaneo-cuboid joint (CCJ) which will, in effect, decrease the distance from the TNJ to the soft tissue restraining structures of the plantar arch (i.e. plantar aponeurosis, plantar intrinsics, plantar ligaments). Supination of the STJ will move the TNJ more dorsal relative to the CCJ so that the distance from the TNJ to the soft tissue restraining structures of the plantar arch will increase. When the thickness of any compression-tension structure increases, whether it is a foot or a beam of wood, its resistance to bending (i.e. stiffness) will increase.

    It is not only the rotational position of the STJ that has a significant effect on the dorsiflexion stiffness at the MTJ. STJ axis spatial location also has a significant effect on MTJ dorsiflexion stiffness since the more medial the STJ axis location, the more plantar the TNJ is relative to the CCJ and the more lateral the STJ axis location is, the more dorsal the TNJ is relative to the CCJ. This "stacking" of the TNJ on top of the CCJ seen both in the foot with a supinated rotational position of the STJ and also in the foot with a laterally deviated STJ axis is the cause for the increased MTJ dorsiflexion stiffness in these feet.

    Therefore, not only does STJ rotational position affect MTJ dorsiflexion stiffness, but also STJ axis spatial location affects MTJ dorsiflexion stiffness since both of these parameters have a direct effect on the three dimensional locations of the TNJ relative to the CCJ and to the "thickness" of the cross-section of the foot from dorsal to plantar at the MTJ level. Because of this, both STJ rotational position and STJ axis spatial location will greatly affect the mechanics of the MTJ and are very closely intertwined with each other and how each foot will respond to dorsiflexion loads from ground reaction force during weightbearing activities. I've known about this concept for over the past two decades but have yet found time to write about it in a fashion that would do it justice.

    Here is what I wrote on this subject in my paper from over a decade ago (Kirby KA: Biomechanics of the normal and abnormal foot. JAPMA, 90:30-34, 2000):

     
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