Why are stiff-soled boots preferred when hiking with heavy pack load?

Kevin, they are measuring the triplane motion at the tibio-talar articulation and at the subtalar joint. They report on the frontal plane component and also the transverse plane component.

 

I'm going to agree with Kevin here. It's hard to see how a fully loaded ankle joint will tend have inversion eversion at the talo tibial joint. Maybe at the time before heel contact and forefoot loading there might be some talo tibial motion. It's hard to see after that unless there are some huge frontal plane moments. I haven't read the paper, but could it be that the small amount of motion could be leading to large percentage changes. If there were only a couple of degrees of frontal plane motion then 1 degree of ankle motion would be a large percentage.

Eric

 

Reporting degrees not percentages from three studies: two bone pin studies, one cadaver simulator study. Read the paper, this is Nesters report not mine. To me the best joint kinematic data we can derive comes from in-vivo bone pin studies. If that's what the data says, that's what it says. If I have to change my thinking in response to this, so be it. To quote Craig- "I'll go where the data takes me" and while I highly respect both your's and Kevin's opinions- the reality is, neither of you have ever measured the motion occurring at the talo-tibial articulation nor the subtalar joint using in-vivo bone pins during gait, whereas these studies did.

So with all due respect, do you have any data to support your contentions? Or are you saying that you just "don't believe the data"?

Read the paper.

 

I just scanned both Nester's and Arndt's paper. I will need to contact either Chris or Tony since it appears that the motion that the talus undergoes on the tibia within the frontal plane in these studies could be partially due to the pronation-supination axis of the ankle joint which would cause talar eversion with ankle joint dorsiflexion and talar inversion with ankle joint plantarflexion, and not necessarily a frontal plane rocking of talus on the tibia inducing a joint gapping within the ankle mortise. This explanation makes the most sense to me.

Interesting discussion. Anyone have the time to move it to a new thread? I've got a few writing projects going on now so I'm short on time.

But, I will say Simon, that I do appreciate you pointing out Nester's data to me since you certainly have made excellent points here and, indeed, I may be wrong as to exactly how calcaneal inversion/eversion occurs during weightbearing activities.

 

Kevin, I am struggling to understand your counter argument. To the best of my knowledge there are a number of studies that have employed bone pins and 3D kinematic analysis to define the movement between the talus and the tibia during gait and between the talus and calcaneus during gait. The movements that occur between either of these two sets of bones allows the researcher to define instantaneous axes of rotation at any given time and to measure the amount of motion in each plane that each bone undergoes. The motion that occur between the talus and the tibia is likely to be a combination of translation and rotation which then defines a single instantaneous axis, hence I don't understand why you are trying to differentiate the movement of "rocking" as a separate entity at this joint, since if it did occur, it's just a component of the overall movement that was observed and does not change the reality that
the data showed that in some individuals the frontal plane component of movement was greater in magnitude at the talo-tibial articulation than at the subtalar articulation what difference does it make whether or not that movement comes from "rocking"?
I look forward to Chris and Tony's replies.

 

I'm just trying to visualize the three-dimensional kinematics of the talus moving on the ankle joint during walking and running and trying to picture whether this frontal plane motion is occurring along the normal axis of rotation of the ankle joint, which is a pronation-supination axis, or whether the talus is twisting inside the ankle joint mortise within the frontal plane causing a relative incongruity within the ankle joint mortise between the talus, tibia and fibula.

I believe that Nester's and Arndt's data is correct. However, anytime a three-dimensional coordinate system is established in an experiment such as theirs, and any time motions occur at a joint that is not perfectly parallel to these orthogonal reference axes, joint motions will occur in all three body planes. I want to know if the data from their experiments represents more of a "frontal plane joint slop" within the ankle joint or more normal (or what we previously considered normal) congruous ankle motion.

In other words, is this frontal motion of the talus relative to the tibia along an ankle joint axis as described by Inman and coworkers, approximately from the tip of the lateral malleolus to the tip of the medial malleolus, or is it more caused by the superior surface of the talus becoming more incongruous with the inferior aspect of the tibial plafond by gapping either medially or laterally away from each other. I believe this is a fundamental question biomechanically that may have important clinical implications in regards to injury mechanisms and joint compliance variability.

 

I don't think that the studies will have attempted to differentiate.

If you had a weightbearing posterior-anterior x-ray of a foot you could assume the subtalar joint was fused and measure a horizontal width across the trochlear surface of the talus and then drop a perpendicular down through the calcaneus from the trochlear width lines centre point. Knowing the length of these two lines you could then rotate them as one about their intercept and use trig to see the relationship between the vertical displacement of the lateral end point of the trochlear surface in mm and the degree of calcaneal eversion. It'll give a ball-park figure to provide an idea of how much "rocking" might be required to achieve the kind of calcaneal eversion magnitudes observed during gait. I'd guess a couple mm of vertical displacement of the lateral aspect of the trochlear surface mm would be sufficient to account for much of the degree of calcaneal eversion observed dynamically.

 

That is why I am interested. These factors would influence the kinetics of talo-tibial motion and the resultant intra-articular talo-tibial and talo-fibular joint pressures which may influence the likelihood of ankle joint articular cartilage and/or subchondral bone injury over time.

 

I think that importance of the distinction that Kevin is making, in addition to what he said, is in determining how those studies are read. Does someone who reads that there is frontal plane motion at the tibio talar joint actually think that there is separation of the bony surfaces. As Kevin pointed out, there is an increased probability of osteoarthritis at the joint if there is. It's quite similar to the external adduction moment on the tibia and medial compartment arthritis of the knee. Is there an increased risk of pathology if there is more frontal plane movement of the ankle. Then if there isn't we can be happy explaining why there isn't with there is a difference between cardinal body plane eversion and the talus twisting in the ankle mortise.

Eric

 

Surely much of the direction of resultant motion between the tibia and the talus is determined by the input force, other joint interactions and the shape of the articulating surfaces. Obviously plastic adaptation of bones can lead to changes in their structural form; plastic adaptation might occur in response to input forces and joint interactions. For example, if we have a patient with a talo-navicular coalition, a ball and socket ankle joint may develop in which the frontal plane motion might be great at the tibio-talar articulation. The ball and socket ankle is an extreme example although couldn't more subtle changes lead to a few degrees of calcaneal eversion being easily achievable at the ankle? Do individuals with ball and socket ankle joints have an increased risk of osteoarthritis? The literature seems to suggest that an absence of osteoarthritic change in ankles with this configuration is the norm. So one must then ask how does the "more common" shape of trochlear surface convert to the ball shape? Is this in response to the talus "rocking" in the ankle mortice?

In this study of subtalar arthrodesis, reductions in tibio-taar articular contact area were observed with some showing lateral displacement of the articular contact region, this suggests to me the talus is "rocking" to achieve calcaneal eversion http://fai.sagepub.com/content/12/1/19.short So, how does subtalar arthrodesis influence the risk of ankle osteoarthritis?

 

I'm a lot happier with rocking can occur than I am with x % of calcaneal frontal plane motion relative to the leg is from rocking. I know the study didn't say that rocking is occurring, but my concern was people would read it that way.

After all, with stress inversion x-rays up to 10 degrees of talar tilt (rocking) is considered normal.

Eric

 

But we don't know that it's not occurring that way i.e. via rocking. Or, do we? Certainly X % of calcaneal frontal plane motion relative to the tibia could be from "rocking". Indeed, as you state:

So, it's seems highly feasible that a high proportion of calcaneal eversion could occur via "rocking" at the tibio-talar articulation, does it not? Ten degrees of talar tilt in concert with an arthrodesis of the subtalar joint should result in 10 degrees of calcaneal eversion.

 

Simon, Eric and Colleagues:

I have moved this very interesting discussion to another thread with a more appropriate title:

Normal and Abnormal Talo-Tibial Kinematics and Kinetics

Let's continue the discussion on talo-tibial biomechanics over there so that this thread on stiff-soled boots isn't totally side-tracked.