Sliding AFDs really necessary for touring boots?

[PeachesNCream]

I'm going to try and summarize in lieu of trying to buy the "safest" binding for my rubber soled AT boots.

1. Skiing in itself is risking your ACL to some extent. Certain bindings may be more or less risky for ACLs but no binding will completely remove this risk.

2. Sliding AFDs without teflon pads may be more risky than non-sliding teflon AFDs.

3. Most of us can agree that sliding teflon AFDs are most-likely safer, when compared to non-sliding AFDs or AFDs without teflon, especially if you have rubber soled boots.

How'd I do?

[DGamms]

DGamms, do you really do 300+ acl repairs or is it reconstructions?

ACL reconstructions, mostly hamstring (semi-t) autograft. Some cadaver allografts too, and a rare BTB patellar tendon now and again.

If the ACL is only partially torn, sometimes the surgeon will just poke at it to theoretically promote increased blood flow and a healing response. Not sure about the data supporting the effectiveness of that.

And to be clear, I don’t do any ACL repairs or reconstructions personally. I’m not a surgeon, so don’t take my word as gospel.

[ExPowderSnob]

My point was that it is extremely shortsighted to claim these sliding AFDs are saving people's ACLs.

I said it was anecdotal, not from a peer reviewed journal... but when experts make an observation, I'll listen..

The phantom foot condition isn't mitigated by a toe release, so the assertion doesn't stand up to a simple free body diagram.

Draw the FBD and share it here. I have an engineering background, I'll understand your point better if you illustrate it. Until then, let me re-state my position.... Here is what it, the mechanically sliding and delrin/teflon frictionally sliding pad combo does do. It creates a redundant load path to allow a toe to laterally slide out of a toe piece part of the binding. If the boot can't slide along the teflon/delrin friction pad for some reason,,, dirt or debris making the mu spike, excessive normal force due to unique circumstances of the crash, etc,, then 2nd path, the physical/ mechanical sliding mechanism can also allow the toe to slide laterally releasing the boot from the binding, hopefully before ligament damage occurs.(of course assuming the DIN isn't cranked to the max).

How can two independent load paths that would allow a boot release not be better than a single path? Redundancy is a good things.. If one fails, the other still works.

It is quite literally misinformation, as it has not been shown to be true and doesn't make sense mechanically. Speaking as someone who has torn their ACL (and both MCLs and meniscuses), I don't think it's responsible to spread misinformation under the guise of it being a professional medical position.

Agree to disagree... Mechanically, fuck yes, it makes sense. It is a redundant load path that allows a boot to exit a binding. Two is better than 1, Redundancy in a critical function is better than a single action in a critical function. Maybe it is my aerospace background here, but for fucks sake, how can you argue against redundant mechanisms for something as important as a release value in a binding? Aerospace ALWAYS has redundancies in flight critical systems. When one system fails, the plane still flies because the 2nd should work. . 737 Crashes are a testament to this.. MCAS had zero redundancy, and people died. If MCAS had a redundant airspeed that could have been checked against the iced sensor, those crashes would have never occurred.

I'm sorry your kneed got fucked. I am sure that was a terrible event to have to recover from. I am not saying that the 2 paths are fool proof and will 100% prevent ACL tears, but I think one can logically see that there is a better chance of a boot releasing at it's designed DIN forces if you have two chances to meet that target.. This is the point I am trying to make.

If I had to choose, (and I did, all but one pair of my bindings are Atomic / Salomon NMC type with the mechanical sliding feature and teflon/delrin slippery plastic), it seems that those double sliding bindings are the way to go.

[detrusor]

One of the surgeons I work with claims that the rise in people skiing AT bindings w soft at boots (you know, they believe the person at REI who says they only need one setup without sacrificing performance anywhere!) is the cause of the increase in tibial plateau fractures. His anecdotal evidence is over 80%. If you add in super side cut skis it approaches 100%.

He says you catch an edge (because you have so little fucking control of the ski) and it gets way out in a “turn” then the slop in the boot is taken up, there is no elasticity in the binding and your tibial plateau goes.


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[macon]

I said it was anecdotal, not from a peer reviewed journal... but when experts make an observation, I'll listen..

Draw the FBD and share it here. I have an engineering background, I'll understand your point better if you illustrate it. Until then, let me re-state my position.... Here is what it, the mechanically sliding and delrin/teflon frictionally sliding pad combo does do. It creates a redundant load path to allow a toe to laterally slide out of a toe piece part of the binding. If the boot can't slide along the teflon/delrin friction pad for some reason,,, dirt or debris making the mu spike, excessive normal force due to unique circumstances of the crash, etc,, then 2nd path, the physical/ mechanical sliding mechanism can also allow the toe to slide laterally releasing the boot from the binding, hopefully before ligament damage occurs.(of course assuming the DIN isn't cranked to the max).

How can two independent load paths that would allow a boot release not be better than a single path? Redundancy is a good things.. If one fails, the other still works.

You're not understanding what I'm saying. Your claim that a lateral release at the toe prevents ACL injury is what I take issue with, because it's proven again and again to be untrue. I already said multiple times in this thread that I prefer a teflon sliding AFD, and I already agree with your redundancy point. Additionally, I've mentioned several other places in this thread where a sliding AFD is beneficial.

I don't want to discuss this much further because I think I've been clear enough already. Lateral release at the heel is required to mitigate the phantom foot condition that leads to ruptured ACLs. Toe release is designed to prevent trauma to the tibia, NOT the ACL. There's extensive testing that has already been done proving this, further, it's why the Knee binding even exists in the first place.

Howell's tests over at wild snow has this very well catalogued, I'd suggest you read the article here:

https://www.wildsnow.com/15123/tech-...cl-broken-leg/


ACL rupture is not mitigated by lateral toe release.

[MagnificentUnicorn]

One of the surgeons I work with claims that the rise in people skiing AT bindings w soft at boots (you know, they believe the person at REI who says they only need one setup without sacrificing performance anywhere!) is the cause of the increase in tibial plateau fractures. His anecdotal evidence is over 80%. If you add in super side cut skis it approaches 100%.

He says you catch an edge (because you have so little fucking control of the ski) and it gets way out in a “turn” then the slop in the boot is taken up, there is no elasticity in the binding and your tibial plateau goes.


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We just fixed a ladies tibial plateau fx, she was skiing in plug boots with race bindings and wc skis. Point being, there are so many variables to this, we’re skiing with long planks fairly well attached to our feet. People are going to get injured.

[roQer]

He says you catch an edge (because you have so little fucking control of the ski) and it gets way out in a “turn” then the slop in the boot is taken up, there is no elasticity in the binding and your tibial plateau goes.


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My tibial plateau went in a Look Pivot 14 with sliding AFD and a Nordica Promachine. You couldn’t exactly speak about little control, albeit in the air time shortly before the crash I wished I was on my touring setup so upon landing everything is gonna to explode and I walk out unscathed.

[macon]

^lol sounds like exactly my thoughts right before my ACL went.

Me at the lip: damn that was a bad pop
Me in the air: shit shit shit.

[ak_powder_monkey]

Look if you just ski with a DIN 16 all the time, this really isn't a problem.

Seriously though I would suspect it is important to keep release values consistently in spec with the TUV standard, I imagine boots with out the AFD plate release correctly sometimes and not others.

[stuckathuntermtn]

I wanna know more about the sewing machine incident.

[1000-oaks]

Lateral release at the heel is required to mitigate the phantom foot condition that leads to ruptured ACLs. Toe release is designed to prevent trauma to the tibia, NOT the ACL. There's extensive testing that has already been done proving this, further, it's why the Knee binding even exists in the first place. ACL rupture is not mitigated by lateral toe release.

This.

Even lateral release at the heel isn't ideal; it would be much better if the heel could drop straight down through the ski (and through the snow, etc) to take tension off the ACL. But that's not possible, so lateral is the next best thing. We just aren't designed to have long sticks strapped to our feet.

I tore mine in mid-air, jumping over the handlebars on a DH bike mid-endo. Quad strength alone can tear it when you reach the limits of your hamstring flexibility. Lessons learned: don't ride like a hack, stretch once in awhile, and stay on the bike until the bitter end.

[turnfarmer]

think the problem Campbell found with the sliding AFds was that the forward pressure broke them, making them immovable. In theory a sliding Teflon AFD would be safer. But if the design failed catastrophically, such as cracking or buckling, it could also prevent release. Testing each would be the only way to know for sure.

[PeachesNCream]

stretch once in awhile

This has a larger effect on preventing ACL injuries (and other injuries) than I think we realize and most of us are pretty bad at.

[macon]

think the problem Campbell found with the sliding AFds was that the forward pressure broke them, making them immovable. In theory a sliding Teflon AFD would be safer. But if the design failed catastrophically, such as cracking or buckling, it could also prevent release. Testing each would be the only way to know for sure.

I'm also curious how much of the rubber toe lugs on the AT boot came in contact with components that were not part of the sliding AFD.

If you look at the pressure sensitive strip he used in his test, it appears as though the boot was in contact with more than just the AFD. Page 72.

[scratchskier321]

No. With a pivot binding, the lateral release is only at the toe. The heel pivots but does not release laterally.

it releases more laterally than a 3 piece heel like tyrolia or sth. those heel's only release upwards... pivot heel can rotate outwards while it releases upwards. so it does have some "lateral" not "pure lateral"... lateral around the circle rotation, not directly 90* off the ski.

[mrkbrnblm]

Purely Anecdotal evidence, by I have now heard from 5 different orthopedic surgeons who swear by the sliding AFD, and won't ski anything else, no matter what the boot is (alpine or touring). Of those, 3 of them say they haven't seen a single patient with ACL tears who had the sliding AFD, the other 2 feel the damage they have seen wasn't as bad as they usually see in serious ACL tears..

I’m another case of a torn ACL (and MCL, and LCL) on a pair of MNC dukes with sliding AFDs. So definitely possible. I still prefer AFDs because I ski inbounds on touring boots, but like others said - they won’t make any difference at all in a “phantom foot” fall which account for the majority of ACL injuries skiing.

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