June Article Discussion – Biomechanical Factors Associated with MTSS and AT

[Scott Resetar]

Attached is an intersting study published online in AJSM recently, performed out at the University of Oregon (quack quack, go ducks). I am by no means a running expert, but I learned a lot about running mechanics in this article, and some things about foot structure clicked that I didn’t have a good mental representation of before I read this. So, here we go.

The researchers discussed the mechanisms that might be similar between Medial Tibias Stress Syndrome (MTSS) and Achilles Tendinopathy (AT). The most cited factor in these conditions in the literature is either an excessive amount of rearfoot eversion, or an excessive velocity of rearfoot eversion. The authors believe however, that only total time spent in rearfoot eversion matters (represented as a % of stance phase)

Here’s the bit about foot structure that really stuck out to me:

“During the first half of stance, as the rearfoot everts, the axes of
the transverse tarsal, cuneonavicular, and tarsometatarsal joints align, allowing the foot to become soft and flexible. During the second half of stance, as the rearfoot supinates, the axes of these joints converge, turning the foot into a rigid lever for use during push-off. Therefore, if eversion is prolonged beyond midstance, then push-off will begin with a soft flexible foot. This configuration may require much greater effort from the intrinsic and extrinsic foot muscles to both stabilize the foot and generate sufficient torque during push-off.”

Makes a lot of sense.

The researchers enrolled 42 runners. 13 with AT, 8 with MTSS, and 21 matched healthy controls. They had them run trials over a force plate and bioreflective markers until they had 8 clean trials, and they averaged the measured variables before they performed their analysis.

Here are the physical characteristics they measured for the study for interactions:

As you can see, significant differences noted in tibial varus angle and dorsiflexion between injured and non injured runners.

Here are the results of the study:

As you can see, the only significant differences between groups was “Period of Pronation” and amount of rearfoot eversion at heel off. Injured runners spent ~85% of their stance phase in rearfoot eversion, versus ~60% for uninjured runners. In addition, the injured group was in about 6 degrees of rearfoot eversion at the instant of heel off, and the uninjured group had achieved an inverted position. It’s kind of confusing due to the negative sign, but the authors state it explicitly in the discussion.

I think this figure made it really stand out for me. Here’s something I can use during gait analysis. I can watch the rearfoot and try to see…Does the patient only invert the rearfoot at the very last 10% of stance phase? or do they appear to achieve an inverted position throughout the last 30-40% of stance?

The authors found that just 3 variables (dorsiflexion ROM, tibial varus angle, and period of pronation), when put into a logistic regression model, were able to correctly classify 81% of runners as injured or non-injured. Every 1% increase in period of pronation increased the odds of being in the injured group by 1.06

Discussion:
1. Overall thoughts on the study? Anything stick out to you that I didn’t mention?

2. What are your thoughts on associations between MTSS and AT? Why are they so similar biomechanically? I didn’t group these conditions together previously, but I sure do now!

3. We have beaten AT to death with our tendinopathy write-ups, but what are your common exam findings and treatments that you use with MTSS patients?

4. For running analysis, what tools do you use in the clinic? We use “Coach My Video”, free version, on our clinic Ipad.(allows slo-mo and frame by frame playback)

5. What cues can we give these patients that won’t just screw them up? (Looking for some input from Eric Magrum on this one). Do we tell them to try to stay on the outside part of the heel, or maybe “get back to the outside of the foot quicker”? Just throwing those out there.

6. What orthotic or taping interventions have you used with patients with AT and MTSS? I’m starting to try more of these in clinic, and I’m eager to see what you guys have up your sleeves.

• This topic was modified 7 years ago by Scott Resetar. Reason: formatting
• This topic was modified 7 years ago by Scott Resetar.

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[Michael McMurray]

What cues can we give these patients that won’t just screw them up? (Looking for some input from Eric Magrum on this one). Do we tell them to try to stay on the outside part of the heel, or maybe “get back to the outside of the foot quicker”?

Increased cadence cues to get people off the ground quicker – less time to pronate through stance when using elastic recoil to spring off the ground with a faster cadence (10% increase ideally).

External cuing with metronome or music best for motor learning; compared to an internal cue like, don’t hit on the outside of your foot.

The difficulties are with older folks (less elastic tendons) to be able to get off the ground quicker; and shifting stress to the Gastroc/Achilles obviously can be problematic with tendinopathy. My experience is that with achilles tendinopathy is that if there is a larger calcaneal EVR at terminal stance (pronation later int stance) they do great with increased cadence cues. May need to be graduated in more slowly.

Also think drills for running – progressively stress the tissues more efficiently.

Thoughts???

[August Winter]

1. Overall thoughts on the study? Anything stick out to you that I didn’t mention?
– Like you mentioned Scott, I thought this article reviewed the relevant gait mechanics in a straightforward way, which is always pleasant. I thought it was interesting that there was a 1:1 ration of the percentage time spent in eversion during stance and the increased risk of injury. I think these sorts of statements help me to remember the important findings more easily. I liked that they called attention to the static morphology of the tibial varum angle and why that might be a factor in the increase eversion time.

2. What are your thoughts on associations between MTSS and AT? Why are they so similar biomechanically? I didn’t group these conditions together previously, but I sure do now!
– I think the most simple way to group these two diagnoses together is by looking at them as diagnoses associated with training error ie improper recovery, improper footwear, large increase in volume etc.

3. We have beaten AT to death with our tendinopathy write-ups, but what are your common exam findings and treatments that you use with MTSS patients?
– I have not seen very many patients with this dx, but I would expect pain with palpation of the posteromedial tibia. I would expect a more cavus foot that has mid and forefoot hypermobilities compared to a hypomobile talocrural joint. I would expect over-pronation with increased loading of the LE kinectic chain: SL balance > SLS > double leg hop. As the motion was more approximated to running (SL hop) I would expect pain provocation. For treatment I would focus on education (inc rest days, dec mileage, improved sleep/nutrition, cross training) first, orthotics to control the pronation in the latter part of stance, intrinsic strengthening, proximal weakness/hypomobilities. Just like with AT the idea is about modifying what you can and then slowly began re-introducing stresses to those tendons.

4. For running analysis, what tools do you use in the clinic?
– We use Hudl. I’m sure others could speak to the positives or negatives of each, but I’ve liked Hudl for the basics.

5. What cues can we give these patients that won’t just screw them up? (Looking for some input from Eric Magrum on this one).
– Cadence, as Eric mentioned, would be my first thought. Besides cadence, you could modify their striking patterns to more of a midfoot strike by cueing them to land softly/quietly. I think this is an external cue that most people can make sense of fairly easily and promotes landing through the mid foot more. As for exercises you could do several variations of things to promote increase supination at toe off. This could be done with a box step up with heel raise focusing on supination, or using the sport cord while doing a heel raise and contralateral high knee into the resistance.

6. What orthotic or taping interventions have you used with patients with AT and MTSS? I’m starting to try more of these in clinic, and I’m eager to see what you guys have up your sleeves.
– As the article mentions, if a runner has a hypermobile midfoot and forefoot and are over-pronating then they wont have a stable base to push off from during terminal stance. I think a motion control orthotic (we use vasyli), possibly with additional medial rearfoot and midfoot posting would be helpful. As we’ve talked about before for AT, a heel lift or medial rearfoot posting would likely decrease the stress through the tendon.

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