newankle

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An orthopod partner of mine asked me the other day "What do you think is the most important joint in the foot biomechanically?". That seemed like an easy answer and explanation for me but what do you all think and why?
 
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Minimal LL anatomy and biomechanics here. Thanks for posting the question, I'm curious to see replies and your answer.

My first instinct is to say the talocrural joint, mostly because it's the first attachment of tibia/fibula to foot, and without that working properly, it doesn't really matter what else is messed up. Am I on the right track?
 
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newankle

newankle

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Minimal LL anatomy and biomechanics here. Thanks for posting the question, I'm curious to see replies and your answer.

My first instinct is to say the talocrural joint, mostly because it's the first attachment of tibia/fibula to foot, and without that working properly, it doesn't really matter what else is messed up. Am I on the right track?
Good point. Most of the surgeries I do are of the ankle and certainly a poorly functioning or painful ankle can be most debilitating but I was looking for a joint within the foot so distal to the tibiotalar joint.
 
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newankle

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1st MTPJ

During toe-off in normal gait and running the center of pressure line goes right through the 1st MTPJ.

1st MTPJ is subject to various foot pathologies such as:
- hallux limitus/rigidus which can affect normal biomechanics and cause abnormal loading of the foot which can produce calluses, ulcerations, etc.
- HAV which can be asymptomatic in some patients while being very painful in others
Very good points and true. I put the 1st MTP joint #3 on my list. There may be no right answer but I still have my #1.
 

shenanigans327

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Not to be cliche, but I might have to go with the STJ. Mind you, I'm a first year just finishing up LEA...but I think that most of what Podiatrists deal in are complications and pathology relating to STJ dysfunction. I also find that just the biomechanics of normal STJ function in closed chain kinetics is fairly complex...
 

dtrack22

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If we're allowed to go with a functional (as opposed to single, anatomical) joint I'd say the Midtarsal joint. I have (what I believe) is a good reason but will have to type that out after work. Just wanted to jump on that before someone beat me to it!
 
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newankle

newankle

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Not to be cliche, but I might have to go with the STJ. Mind you, I'm a first year just finishing up LEA...but I think that most of what Podiatrists deal in are complications and pathology relating to STJ dysfunction. I also find that just the biomechanics of normal STJ function in closed chain kinetics is fairly complex...
Subtalar joint is my #2.
 

air bud

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I would go with the MTJ. Multiple ways for it to unluck and become unstable, leading to very common problems such as HAV and HL/HR. My first guess was the STJ in all honesty though.
 
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newankle

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I like the reasons stated for the midtarsal joint and 1st tarsometatarsal joint but the excursions here are minimal. My #1 is the talonavicular joint. Part of the reason is what you stated for these other joints. In school I got the feeling it was the STJ but after being in practice, dealing with things that work and don't and asking why, playing around with isolated joint fusions and such I have the most respect for the under appreciated TN joint. You likely don't get to see many isolated TN fusions but when you do, you will also have this appreciation I think. I think it can be both the most stabilizing and destabilizing joint of the foot. Look at the extremes. In an extreme flexible flatfoot it is the fulcrum about which the entire foot swings and deforms. Stabilizing this articulation/maintaining congruence is the key to success. TN arthrodesis has the single biggest effect on both the STJ range of motion and midtarsal joint range of motion so those of you that argue midtarsal joint should understand that. What happens when you fuse the joints you chose? Fuse the 1st MTPJ - so what, not much effect on hindmost or even midfoot. Fuse the midtarsal joints - this affects the rearfoot if there's not enough motion available to accommodate but actually even if the rearfoot is in valgus or varus you can still get by with adequate TN motion. I think it's a toss up between STJ and TN but like TN better. 2 cases of mine in the past that helped bring home this point to me are #1 a patient that had a displaced navicular body fx I did ORIF on and did well. 3 years later in another motocross injury he crushed the navicular (and broke mets 2,3, and ankle) so I ended up doing a TN fusion after the 2nd fracture. I was amazed at how that stabilized his foot. Previously he had a flexible flatfoot but that really stabilized the entire medial column and he did well. It also made the STJ stiff as heck. #2 is a patient I did an open tibiotalar fusion with syndesmotic fusion/fibula onlay graft. This patient I was worried about b/c was my 1st ankle fusion in private practice and at 10 weeks X-rays suggested solid fusion but clinically he could dorsiflex some. When stressed under fluoro there was no motion at the tibiotalar joint but it was occurring at the TN and midtarsus and CT confirmed solid fusion. This motion showed me there is more motion available there than I realized.
 
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newankle

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Also where do you see AVN in the foot most often (other than freiberg's)? Talus and/or navicular. Why? Yes some of it may be vascular anatomy, some may be systemic dz, but from a mechanical standpoint there is a lot of compression/pressure at that TN joint and I think that may be an underestimated point.
 

dtrack22

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Makes sense. And if I had to pick between TN and CC I would have picked the TN due to the importance of the medial column and the likelihood (or lack thereof) of lateral column pathologies due to a normal to supinated foot type. My reasoning was similar to everyone else's thinking. The MTJ has a rather extensive range of motion (and it is triplanar), as well as having a direct affect on wether the entire foot is stable or rigid based on it's axes (rather "axis", singular :) ) of motion. So while the STJ may act on the MTJ, the midtarsal is the joint in which RR and FF motion must occur through in order to affect or compensate for the other.

The more I read, the less I feel like the STJ is the end-all-be-all that students can be led to believe in school. Yes, it is very very very very important...but I still think every once in awhile we should look outside of the STJ for explanations and treatments of foot pathology.

Anyways, thanks for the post newankle. Interesting. Forced me to do some review too!
 

jdikis

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I like the reasons stated for the midtarsal joint and 1st tarsometatarsal joint but the excursions here are minimal. My #1 is the talonavicular joint. Part of the reason is what you stated for these other joints. In school I got the feeling it was the STJ but after being in practice, dealing with things that work and don't and asking why, playing around with isolated joint fusions and such I have the most respect for the under appreciated TN joint. You likely don't get to see many isolated TN fusions but when you do, you will also have this appreciation I think. I think it can be both the most stabilizing and destabilizing joint of the foot. Look at the extremes. In an extreme flexible flatfoot it is the fulcrum about which the entire foot swings and deforms. Stabilizing this articulation/maintaining congruence is the key to success. TN arthrodesis has the single biggest effect on both the STJ range of motion and midtarsal joint range of motion so those of you that argue midtarsal joint should understand that. What happens when you fuse the joints you chose? Fuse the 1st MTPJ - so what, not much effect on hindmost or even midfoot. Fuse the midtarsal joints - this affects the rearfoot if there's not enough motion available to accommodate but actually even if the rearfoot is in valgus or varus you can still get by with adequate TN motion. I think it's a toss up between STJ and TN but like TN better. 2 cases of mine in the past that helped bring home this point to me are #1 a patient that had a displaced navicular body fx I did ORIF on and did well. 3 years later in another motocross injury he crushed the navicular (and broke mets 2,3, and ankle) so I ended up doing a TN fusion after the 2nd fracture. I was amazed at how that stabilized his foot. Previously he had a flexible flatfoot but that really stabilized the entire medial column and he did well. It also made the STJ stiff as heck. #2 is a patient I did an open tibiotalar fusion with syndesmotic fusion/fibula onlay graft. This patient I was worried about b/c was my 1st ankle fusion in private practice and at 10 weeks X-rays suggested solid fusion but clinically he could dorsiflex some. When stressed under fluoro there was no motion at the tibiotalar joint but it was occurring at the TN and midtarsus and CT confirmed solid fusion. This motion showed me there is more motion available there than I realized.
This is the correct answer. See the article by Astion in JBJS (http://jbjs.org/article.aspx?Volume=79&page=241) about isolated fusion of each component of the tritarsal complex. Also look up "essential" vs. "non-essential" joints of the foot in Hansen's book Functional Reconstruction of the Foot and Ankle. (http://books.google.com/books?id=ASSCGDRC-KsC&pg=PA31&dq=essential+non-essential+joints+foot&hl=en&sa=X&ei=MX6qT8OlL4aw8ATa27HnDA&ved=0CEUQ6AEwAA#v=onepage&q=essential%20non-essential%20joints%20foot&f=false).
I'm not saying the other joints aren't important, however the TN has the most influence on pedal motion within the foot.
I think the talocrural joint is a separate entity from the foot, so is left out of the discussion.
Good question posed by the OP.
All links credited to original authors.
 

NeilD

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An orthopod partner of mine asked me the other day "What do you think is the most important joint in the foot biomechanically?". That seemed like an easy answer and explanation for me but what do you all think and why?

The most important joint in the foot? How about the little white one that that you placed between your toes coming back from the beach when you are pulled over by the cops?
 

dtrack22

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newankle,

Have you moved more towards doing a medial double (TNJ and STJ) in patients that traditionally would have undergone a triple arthodesis? Just curious. Seems applicable based on your comments about the TNJ and we've had a few guest lecturers lately who have both discussed their shift away from arthrodesing the CCJ.
 

Ferocity

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The most important joint in the foot? How about the little white one that that you placed between your toes coming back from the beach when you are pulled over by the cops?
:laugh:
 
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1st MTPJ

During toe-off in normal gait and running the center of pressure line goes right through the 1st MTPJ as you are pronating the foot.

1st MTPJ is subject to various foot pathologies such as:
- hallux limitus/rigidus which can affect normal biomechanics and cause abnormal loading of the foot which can produce calluses, ulcerations, etc.
- HAV which can be asymptomatic in some patients while being very painful in others
:thumbup: