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I'll have to see if I can find my paper copy and scan it in Ian. In the garage somewhere! Maybe someone can save me the effort and pdf it?
Unfortunately, these researchers pinned the talus to the tibia to do their experiments. Therefore, I was not very impressed with the unphysiologic setup for the cadaver feet in this research. In addition, I definitely didn't like the title. How does a spring lock?.......answer......it doesn't!!
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Unfortunately, these researchers pinned the talus to the tibia to do their experiments. Therefore, I was not very impressed with the unphysiologic setup for the cadaver feet in this research.
Wasn't that just to get control of the talus so they could invert and evert the reafoot with close coupling via the tibia? How might this pinning influence the observed results at the midfoot?
I'm not too fussed about the locked terminology: my front door is locked right now, if I push on it it doesn't move, if I kick hard enough it will. Is it locked? Sure is. Similarly, the midtarsal joint will reach a position in which physiological loading levels will result in no further visible deformation, only by exceeding this physiological loading will further visible deformation occur. But lets leave the semantics to one side for now. Why should pinning the talus to the leg influence the observed midtarsal motion? Moreover, why does rearfoot position apparently not influence forefoot inversion and eversion range of motion yet apparently does influence the sagittal plane motion?
I don't comprehend. If an axis is rotated in the transverse plane to increase sagittal plane rom then doesn't this rotation DECREASE the frontal plane rom?
I'm not too fussed about the locked terminology: my front door is locked right now, if I push on it it doesn't move, if I kick hard enough it will. Is it locked? Sure is. Similarly, the midtarsal joint will reach a position in which physiological loading levels will result in no further visible deformation, only by exceeding this physiological loading will further visible deformation occur.
I thought that you would immediately understand the importance of the not viewing the midtarsal/midfoot joints as "locking", any more than you would describe the spring in the leg being "locked" in any one position in the bipedal spring-mass model of walking or even in the spring-mass model of running.
Are you saying then that we should viewing the midtarsal joint less like a leaf-spring and more as a ratcheting wrench that locks incrementally into a new position of function with each few degrees of rotation? Or rather should we view the midtarsal joint, as you stated above, as a door that closes and locks and will only move further when a significantly higher threshold force (i.e. kicking the door off its hinges and breaking through the door facing) will cause it to rotate further, breaking structural components of the foot along the way? Does the midtarsal "lock" into one position of function during standing, then "lock" in another position during running, and then "lock" into another position during high jumping like a door that locks into it's frame? Aren't these all "physiological loading" conditions for each of these specific activities? The fluoroscopic video that I have from Don Green of feet walking both barefoot and in shoes and the available research on the spring-like function of the foot clearly indicates to me the midtarsal and midfoot joint are spring-like in nature, and not "locking like a door" as you describe above.
Quote:
Originally Posted by Simon Spooner
Why should pinning the talus to the leg influence the observed midtarsal motion?
Because without the ability of the talus to move independently of the tibia as it does physiologically during loading and unloading of the plantar foot, along with the associated increasing and decreasing in magnitudes of tensile forces within the Achilles tendon and plantar fascia and plantar ligaments, one would simply be guessing as to what the change in stiffness (i.e. a measurement of spring-like materials/structures) within the midtarsal/midfoot joint complex would be with these changes in external and internal moments and forces acting on and within the foot were made during the cadaver experiment. In other words, unless the talus can move independent of the tibia and calcaneus, normal midtarsal joint, subtalar joint and ankle joint motions and the corresponding plantar ligamentous restraining forces can not be physiologically simulated in a weightbearing cadaver experiment,. However, pinning the talus to the tibia could give you a good idea in a weightbearing cadaver experiment of how an ankle joint arthrodesis procedure may affect the kinetics of the midtarsal joint versus a foot with normal talo-tibial joint motion.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Wasn't that just to get control of the talus so they could invert and evert the reafoot with close coupling via the tibia? How might this pinning influence the observed results at the midfoot?
Simon, Kevin,
I'm with Simon on this one. There is information that can be leared about the range of motion that is limited by the ligaments and articular surfaces of the MTJ. This information is independent of Achilles tendon tension and other things. If you wanted to examine the range of motion of the Midtarsal joint, it is perfectly logical to pin the talus to the tibia.
I've written about my "doorstop" theory of midtarsal joint motion on various forums before, but I will repeat it here. One of the structures that limits dorsiflexion of the midtarsal joint is the dorsal aspect of the joint. The article in question did not look at transverse plane motion, but it is also important. Transverse plane motion of the MTJ is limited, in part, by the lateral aspect of the calcaneal cuboid joint. Looking at the anterior facet of the calcaneus, the medial part of the joint is curved and the lateral part is flat. As the forefoot (cuboid) adducts and plantar flexes the lateral part of the cc joint separates. As the forefoot abducts the flat parts abut to prevent further motion. So, the lateral part of the cc joint is the door stop.
With STJ pronation there is an anterior break of the cyma line. This is seen on a lateral radiograph where the anterior surface of the talus is more anterior than the anterior surface of the calcaneus. When the STJ is radiographed in a more supinated position the anterior surface of the talus is more posterior relative to the anterior surface of the calcaneus than when the foot is radiographed in a more pronated position of the STJ. The door stop moves. This is why there is less range of motion of the MTJ when the foot is in a more supinated position when compared to a more pronated position.
This same effect is seen in a an Evans opening wedge calcaneal osteotomy. In this procedure a chisel is oriented vertically and driven from medial to lateral at the lateral aspect of the calcaneus about 1/4 of its length from the anterior aspect. The bone is pried apart and bone graft is inserted essentially lengthening the calcaneus (and moving the doorstop further forward.) A decrease in range of motion of the MTJ is seen with this procedure.
I'm not quite sure that was your original question Simon. But that's my two cents.
Why do you think rearfoot position influenced sagittal plane motion, but not frontal plane motion?
Ah, the original question. To add to my previous post. The frontal plane relationship of the bones of the MTJ change much less than the transverse and sagital plane relationships. I haven't read the article, but am curious about how they looked at sagittal plane motion without examining transverse plane motion. Was the motion evaluation using a global reference or a single bone reference point.
I'm with Simon on this one. There is information that can be leared about the range of motion that is limited by the ligaments and articular surfaces of the MTJ. This information is independent of Achilles tendon tension and other things. If you wanted to examine the range of motion of the Midtarsal joint, it is perfectly logical to pin the talus to the tibia.
I've written about my "doorstop" theory of midtarsal joint motion on various forums before, but I will repeat it here. One of the structures that limits dorsiflexion of the midtarsal joint is the dorsal aspect of the joint. The article in question did not look at transverse plane motion, but it is also important. Transverse plane motion of the MTJ is limited, in part, by the lateral aspect of the calcaneal cuboid joint. Looking at the anterior facet of the calcaneus, the medial part of the joint is curved and the lateral part is flat. As the forefoot (cuboid) adducts and plantar flexes the lateral part of the cc joint separates. As the forefoot abducts the flat parts abut to prevent further motion. So, the lateral part of the cc joint is the door stop.
With STJ pronation there is an anterior break of the cyma line. This is seen on a lateral radiograph where the anterior surface of the talus is more anterior than the anterior surface of the calcaneus. When the STJ is radiographed in a more supinated position the anterior surface of the talus is more posterior relative to the anterior surface of the calcaneus than when the foot is radiographed in a more pronated position of the STJ. The door stop moves. This is why there is less range of motion of the MTJ when the foot is in a more supinated position when compared to a more pronated position.
This same effect is seen in a an Evans opening wedge calcaneal osteotomy. In this procedure a chisel is oriented vertically and driven from medial to lateral at the lateral aspect of the calcaneus about 1/4 of its length from the anterior aspect. The bone is pried apart and bone graft is inserted essentially lengthening the calcaneus (and moving the doorstop further forward.) A decrease in range of motion of the MTJ is seen with this procedure.
I'm not quite sure that was your original question Simon. But that's my two cents.
Eric
Eric:
I'll need to get the paper out and read it again. I don't like any cadaver study that tries to simulate weightbearing function of a joint of the foot but does not load both the tibia and the Achilles tendon. This would especially be important in trying to understand the change in stiffness within the midtarsal joint with weightbeaing of the foot.
What would have prevented these researchers from studying midtarsal joint stiffness without pinning the talus to the tibia? Was the pathological situation of effectively creating an ankle arthrodesis actually necessary to effectively study midtarsal joint kinetics? I don't think so.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
I thought that you would immediately understand the importance of the not viewing the midtarsal/midfoot joints as "locking", any more than you would describe the spring in the leg being "locked" in any one position in the bipedal spring-mass model of walking or even in the spring-mass model of running.
Are you saying then that we should viewing the midtarsal joint less like a leaf-spring and more as a ratcheting wrench that locks incrementally into a new position of function with each few degrees of rotation? Or rather should we view the midtarsal joint, as you stated above, as a door that closes and locks and will only move further when a significantly higher threshold force (i.e. kicking the door off its hinges and breaking through the door facing) will cause it to rotate further, breaking structural components of the foot along the way? Does the midtarsal "lock" into one position of function during standing, then "lock" in another position during running, and then "lock" into another position during high jumping like a door that locks into it's frame? Aren't these all "physiological loading" conditions for each of these specific activities? The fluoroscopic video that I have from Don Green of feet walking both barefoot and in shoes and the available research on the spring-like function of the foot clearly indicates to me the midtarsal and midfoot joint are spring-like in nature, and not "locking like a door" as you describe above.
Kevin, I think you know me well enough to believe that I have a reasonable comprehension of foot biomechanics; enough to understand the difference between joint stiffness and "locking". I was merely trying to say that even when we call something "locked" like a door, that it is only showing a high degree of stiffness and that with enough force applied it will deform. What I was REALLY trying to say, is that I didn't want to get into a debate about the use of the term "locked" by the authors of the paper, but was rather more interested in why the range of motion altered in one plane and not the other?
Quote:
Originally Posted by Kevin Kirby
Because without the ability of the talus to move independently of the tibia as it does physiologically during loading and unloading of the plantar foot, along with the associated increasing and decreasing in magnitudes of tensile forces within the Achilles tendon and plantar fascia and plantar ligaments, one would simply be guessing as to what the change in stiffness (i.e. a measurement of spring-like materials/structures) within the midtarsal/midfoot joint complex would be with these changes in external and internal moments and forces acting on and within the foot were made during the cadaver experiment. In other words, unless the talus can move independent of the tibia and calcaneus, normal midtarsal joint, subtalar joint and ankle joint motions and the corresponding plantar ligamentous restraining forces can not be physiologically simulated in a weightbearing cadaver experiment,. However, pinning the talus to the tibia could give you a good idea in a weightbearing cadaver experiment of how an ankle joint arthrodesis procedure may affect the kinetics of the midtarsal joint versus a foot with normal talo-tibial joint motion.
I guess it depends on the question you are trying to answer. If we want to control for variation in the shank position, then fusing the tibia and talus would seem reasonable.
Kevin, I think you know me well enough to believe that I have a reasonable comprehension of foot biomechanics; enough to understand the difference between joint stiffness and "locking". I was merely trying to say that even when we call something "locked" like a door, that it is only showing a high degree of stiffness and that with enough force applied it will deform. What I was REALLY trying to say, is that I didn't want to get into a debate about the use of the term "locked" by the authors of the paper, but was rather more interested in why the range of motion altered in one plane and not the other?
I wasn't going to respond to your use of the term "locked" for the midtarsal joint until you used the door example, which I think needed some clarification. The title of the thread is "midtarsal joint locking"......so I figured it was fair game.
The reason I get so bothered by the term "locked"when we speak of joint position with the midtarsal/midfoot joints is because I believe that the use of such a term infers a non-spring-like mechanical function to the foot, which we rather know to be spring-like. When an automobile is resting on the ground and the springs in its suspension are not moving, do we say these springs are "locked"? No, we don't use this term because we know if we added more load to the axle the springs would simply compress more to the load applied. In much the same way, we should understand that the position that the midtarsal joint seen during manual examination, with relatively low loads, may be a quite different position than the midtarsal joint position at higher loads such as during quiet standing. The midtarsal joint doesn't "lock" into a position any more than any other spring "locks" into one position during deformation, it simply becomes "temporarily stable to load".
Quote:
I guess it depends on the question you are trying to answer. If we want to control for variation in the shank position, then fusing the tibia and talus would seem reasonable.
I would agree that the type of question that is trying to be answered will determine how cadaver experiments are performed. However, I see so much cadaver research being done just with loading forces through the tibia and without the Achilles tendon being loaded or tethered which does not realistically recreate the bending moments through the midtarsal joint or other joints of the foot for that matter. I guess what I am saying is that when I read this paper that I thought their poor experimental setup of the cadavers was so unnatural that it couldn't add anything new to my knowledge of normal foot function. However, fusing the ankle would be good to study the effects of ankle arthrodesis on midtarsal joint function.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
I'll need to get the paper out and read it again. I don't like any cadaver study that tries to simulate weightbearing function of a joint of the foot but does not load both the tibia and the Achilles tendon. This would especially be important in trying to understand the change in stiffness within the midtarsal joint with weightbeaing of the foot.
What would have prevented these researchers from studying midtarsal joint stiffness without pinning the talus to the tibia? Was the pathological situation of effectively creating an ankle arthrodesis actually necessary to effectively study midtarsal joint kinetics? I don't think so.
Quote:
CONCLUSIONS: This study demonstrated that motion in the forefoot is influenced by hindfoot position through the midtarsal joint. Specifically, the sagittal plane range of motion of the metatarsals is increased when the hindfoot is in valgus.
The study is not trying to simulate weight bearing function, but mearly trying to examine range of motion. There certainly is a problem when people try to extrapolate the results of this study to weight bearing midtarsal joint properties. That faulty extrapolation is what has given us the rigid lever/ mobile adapter crap.
Some people also tend to forget that there are two different values for stiffness of the joint. When some one is seated and you grab, and move their forefoot, and hold the calcaneus stationary you should find some radically different values for stiffness. There is the "physiologic" range of motion where the ligaments are not tight. Then as you keep trying to move the joint in a certain direction, the ligaments will become tight (or in other joints you'll get bone on bone contact) and the joint will become a lot stiffer.
Function of the joint loaded is probably looking at the stiffness values at the end of "physiologic" range of motion. A good question is whether or not the decrease in the physiologic range of motion with STJ supination effects the stiffness when loaded. To evaluate that you'd probably need to fuse the STJ in various positions. Then, if you found a difference in rigidity you'd have to figure out if you could get the STJ to reach equilibrium in that more supinated position. So, the paper did find a difference in physiologic range of motion (as did Daryl Phillips in 1983). However, that is just the first step on figuring out if that has any relation to weight bearing function.
(The ability to change the STJ position of equilibrium is also important for STJ axis location discussions. Yes, the STJ axis moves with pronation and supination, but can you acieve STJ equilibrium so that the STJ sits in a significantly more supinated position.) Sta peg / arthoresis is one method that comes to mind. Further research in this area could help better define the indications for arthroresis of the STJ.
Ah, the original question. ... The frontal plane relationship of the bones of the MTJ change much less than the transverse and sagital plane relationships. ..
This changed relationship would have to be between the anterior surface of the talus relative to the anterior surface of the calcaneus, correct? I'm so far behind you gents just trying to follow, mark
This changed relationship would have to be between the anterior surface of the talus relative to the anterior surface of the calcaneus, correct? I'm so far behind you gents just trying to follow, mark
Mark, as we are talking midtarsal joint, it has to be the relationships between the talus and navicular and calcaneus and cuboid (given a rigid body approximation at the navicular cuboid articulation).
My thanks to Kevin for the full text. This is interesting:
"Unexpectedly, we found a nonsignificant trend of
increased range of motion of the navicular in the
frontal plane from forefoot dorsiflexion to plantarflexion
when the hindfoot was inverted compared to everted
(Table 2, p = 0.06). The cuboid data for the same
loading conditions also increased when the hindfoot
was inverted, but the difference was not significant
(p = 0.3)."
So while rearfoot inversion decreased sagittal plane motion, it increased frontal plane motion. What, if any, are the implications of this to the theory of calcaneocuboid locking presented by Bojsen-moller? Here: http://mortonsfoot.com/articles/calcaneocuboidjoint.pdf
This changed relationship would have to be between the anterior surface of the talus relative to the anterior surface of the calcaneus, correct? I'm so far behind you gents just trying to follow, mark
Pretty much. What we are looking at is what limits motion (or causes increased stiffness as some point, in the available range of motion. My discussion above makes more sense in the transverse plane as compared to the sagittal plane. As you look at an a-p xray with STJ in a pronated and then a supinated position you will see the anterior facets of the talus and the calcaneus much farther apart when the STJ is pronated. When the STJ is pronated, the forefoot will be able to abduct further, relative to the talar head because it has to travel farther before the flat parts of the cc joint abut.
Mark, as we are talking midtarsal joint, it has to be the relationships between the talus and navicular and calcaneus and cuboid (given a rigid body approximation at the navicular cuboid articulation).
Gday Simon, where the navicular-cuboid posterior surfaces can go depends on the relationship between talus and calcaneal anterior surfaces, that's what i was trying to say. the triplane change in the STJ axis? affects the talo-calcaneal anterior surface relationship, the navicular-cuboid 'follow'? Being pedantic, yep, just thinking it through as I've got to get things right in order for my 'brain' to follow a discussion.
Love the thread, even if there is a mini bitchfight on the side. But with the BIG 3 involved I'm very keen to understand.
Love the thread, even if there is a mini bitchfight on the side. But with the BIG 3 involved I'm very keen to understand.
Mark:
Actually, the "bitchfight" was all staged in order to promote the popularity of this thread. When Simon threw me out of the Big Time Podiatry Arena Ring onto my head, I just popped one of those "fake blood capsules" into my mouth and bit down so that it only looked like there was blood streaming out of my mouth. Sorry for the let-down.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Sorry you are having some difficulty following our discussion. In reading back through your questions, it is probably best if you just totally forget about the notion that both the calcaneo-cuboid (CC) joint and talo-navicular (TN) joint have independent joint axes that criss-cross during supination and then become parallel during pronation, as first described by Efltman a half century ago (Elftman, H.: The transverse tarsal joint and its control. Clin. Orthop., 16:41-44, 1960.) This was a guess by Elftman and, in my opinion, was totally wrong. Unfortunately, Root et al decided to accept his explanation and put it in their book, which has given it more credibility in the last few decades.
The midtarsal joint (MTJ) motion will tend to change with pronation and supination of the subtalar joint(STJ). This change in MTJ motion occurs not so much due to a change in position of two imaginary joint axes in the CC joint and TN joint as Elftman claimed, but likely are more due to the change in the spatial location of the CC joint relative to the TN joint in the STJ pronated and supinated position.
With STJ supination, the TNJ is more superiorly "stacked" on top of the CCJ which will create a greater stiffness at the MTJ to forefoot dorsiflexion relative to the rearfoot when compared. However, when the STJ is pronated and the TNJ is more medially positioned to the CCJ and the dorsal-plantar thickness of the MTJ is reduced which makes the MTJ have greater sagittal plane compliance. The foot, therefore, is similar to a 2x4" piece of lumber and the increase in stiffness of that board when that board is placed upright on it's 2" edge versus when the board is placed flat on its 4" side, which makes it more thin and have more compliance which doens't resist sagittal plane deformation as well as when the STJ is supinated.
Remember that the structures that restrain MTJ motion are the plantar ligaments and plantar fascia. These plantar tensile load-bearing structures are some of the main structures that determine the kinematics and kinetics of the MTJ and are much more important than any imaginary joint axes you have seen in textbooks or lectures over the years.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Thanks Kevin, it wasn't the Elftman oblique and long? midtarsal axes hypothesis that i was hung up on. I'll stay out of this thread now.
But this is excellent, this will sink in.
Quote:
Originally Posted by Kevin Kirby
...With STJ supination, the TNJ is more superiorly "stacked" on top of the CCJ which will create a greater stiffness at the MTJ to forefoot dorsiflexion relative to the rearfoot when compared. However, when the STJ is pronated and the TNJ is more medially positioned to the CCJ and the dorsal-plantar thickness of the MTJ is reduced which makes the MTJ have greater sagittal plane compliance. The foot, therefore, is similar to a 2x4" piece of lumber and the increase in stiffness of that board when that board is placed upright on it's 2" edge versus when the board is placed flat on its 4" side, which makes it more thin and have more compliance which doens't resist sagittal plane deformation as well as when the STJ is supinated.
Remember that the structures that restrain MTJ motion are the plantar ligaments and plantar fascia. These plantar tensile load-bearing structures are some of the main structures that determine the kinematics and kinetics of the MTJ and are much more important than any imaginary joint axes you have seen in textbooks or lectures over the years.
Midtarsal joint "locking"
Linear Mode
