Welcome to Rewind Friday, Folks. Today we review the importance of the great toe extensor. Enjoy!

Gait Topic: The Mighty EHB (The Short extensor of the big toe, do not dismiss it !)

Look at this beautiful muscle in a foot that has not yet been exposed to hard planar surfaces and shoes that limit or alter motion! (2 pics above, toggle back and forth)

The Extensor Hallicus Brevis, or EHB as we fondly call it (beautifully pictured above causing the  extension (dorsiflexion) of the child’s proximal big toe) is an important muscle for descending the distal aspect of the 1st ray complex (1st metatarsal and medial cunieform) as well as extending the 1st metatarsophalangeal joint. It is in part responsible for affixing the medial tripod of the foot to the ground.  Its motion is generally triplanar, with the position being 45 degrees from the saggital (midline) plane and 45 degrees from the frontal (coronal) plane, angled medially, which places it almost parallel with the transverse plane. With pronation, it is believed to favor adduction (reference). Did you ever watch our video from 2 years ago ? If not, here it is, you will see good EHB demo and function in this video. click here

It arises from the anterior calcaneus and inserts on the dorsal aspect of the proximal phalynx. It is that quarter dollar sized fleshy protruding, mass on the lateral aspect of the dorsal foot.  The EHB is the upper part of that mass. It is innervated by the lateral portion of one of the terminal branches of the deep peronel nerve (S1, S2), which happens to be the same as the extensor digitorum brevis (EDB), which is why some sources believe it is actually the medial part of that muscle. It appears to fire from loading response to nearly toe off, just like the EDB; another reason it may phylogenetically represent an extension of the same muscle.

*The EDB and EHB are quite frequently damaged during inversion sprains but few seem to ever look to assess it, largely out of ignorance. We had a young runner this past year who had clearly torn just the EHB and could not engage it at all. He was being treated for lateral ankle ligament injury when clearly the problem was the EHB, the lateral ligamentous system had healed fine and this residual was his chief problem.  Thankfully we got the case on film so we will present this one soon for you !  In chronic cases we have been known to take xrays on a non-standard tangential view (local radiographic clinics hate us, but learn alot from our creativity) to demonstrate small bony avulsion fragments proving its damage in unresolving chronic ankle sprains not to mention small myositis ossificans deposits within the muscle mass proper.

Because the tendon travels behind the axis of rotation of the 1st metatarsal phalangeal joint, in addition to providing extension of the proximal phalynx of the hallux (as seen in the child above), it can also provide a downward moment on the distal 1st metatarsal (when properly coupled to and temporally sequenced with the flexor hallicus brevis and longus), assisting in formation of the foot tripod we have all come to love (the head of the 1st met, the head of the 5th met and the calcaneus).

Wow, all that from a little muscle on the dorsum of the foot.

The Gait Guys. Definitive Foot Geeks. We are the kind of people your podiatrist warned you about…

The Power of Facilitation: How to supercharge your run.

While running intervals this crisp, cool 19 degree morning, something dawned on me. My left knee was hurting from some patellar tracking issues, but only on initial contact and toe off. I generally run with a midfoot strike. I began concentrating on my feet, lifted and spread my toes and voila! my knee pain instantly improved. Very cool, and that is why I am writing this today. 

Without getting bogged down in the mire of quad/hamstring facilitation patterns, lets look at what happened.

I contracted the long extensors of the toes: the extensor digitorum longus and the extensor hallicus longus; the short extensors of my toes: the extensor digitorum brevis, the extensor hallucis brevis: as well as the dorsal interossei.the peroneus longus, brevis and tertius were probably involved as well.

Do you note a central theme here? They are all extensors. So what, you say. Hmmm… 

Lets think about this from a neurological perspective:

In the nervous system, we have 2 principles called convergence and divergence. Convergence is when many neurons synapse on one (or a group of fewer) neuron(s). It takes information and “simplifies” it, making information processing easier or more streamlined. Divergence is the opposite, where one(or a few) neurons synapse on a larger group. It takes information and makes it more complicated, or offers it more options.

In the spinal cord, motor neurons are arranged in sections or “pools” as we like to call them in the gray matter of the cord. These pools receive afferent information  and perform segmental processing (all the info coming in at that spinal cord segment) before the information travels up to higher centers (like the cerebellum and cortex). One of these pools fires the extensor muscles and another fires the flexor muscles.. 

If someone in the movie theater keeps kicking the back of our seat, after a while, you will say (or do) something to try and get them to stop. You have reached the threshold of your patience. Neurons also have a threshold for firing.  If they don’t reach threshold, they don’t fire; to them it is black and white. Stimuli applied to the neuron either takes them closer to or farther from threshold.  When a stimulus takes them closer to firing, we say they are “facilitating” the neuron. If it affects a “pool” of neurons, then that neuronal pool is facilitated. If that pool of neurons happens to fire extensor muscles, then that “extensor pool” is facilitated.

When I consciously fired my extensor muscles, two things happened: 1. Through divergence, I sent information from my brain (fewer neurons in the cortico spinal pathway) to the motor neuron pools of my extensor muscles (larger groups of motor neurons) facilitating them and bringing them closer to threshold for firing and 2. When my extensor muscles fired, they sent that information (via muscle spindles, golgi tendon organs, joint mechnoreceptors, etc) back to my cerebellum, brain stem and cortex (convergence) to monitor and modulate the response.

When I fired my extensor muscles, I facilitated ALL the neuronal pools of ALL the extensors of the foot and lower kinetic chain. This was enough to create balance between my flexors and extensors and normalize my knee mechanics.

If you have followed us for any amount of time, you know that it is often “all about the extensors” and this post exemplifies that fact.

 Next time you are running, have a consciousness of your extensors. Think about lifting and spreading our toes, or consciously not clenching them. Attempt to dorsiflex your ankles and engage your glutes. It just may make your knees feel better!

The Gait Guys. Facilitating your neuronal pools with each and every post.

All material copyright 2013 The Gait Guys/ The Homunculus Group. All rights reserved. If you rip off our stuff, we will send Lee after you!

A case of the non-resolving ankle sprain.  Things to think about when the ankle and foot just do not fully come around after a sprain.

Gait Guys,

A while back I had a severe ankle sprain while trail running.  As I stepped on a rock my toes pointed downward, my ankle was rolled in and I felt a pop. This was follow by a lot of swelling and bruising both on the inside and outside of my ankle.  Being experienced with ankle sprains, I jumped on the initial treatment immediately. The reduction in swelling and bruising lead me to believe that I was in for a 4-5 week recovery, then I would be back at what I love doing. I was proven wrong:  

1.       Initial treatment consisted of immobilization, icing, and a very high dose of Ibuprofen (3 days only). After a couple weeks of this I began stretching, massage and trying to get into some modified activities as the pain allowed me to. I was able to  do some hiking but running was too painful.

2.       After 6 weeks, I was still having pain in the posterior tibial tendon area as well as the deltoid ligament area. I tried running but, I was met with severe pain beginning in the middle of the gait cycle through  the push off. I saw a PA at this time and was told to give it more rest. For the next few weeks I wore a soft brace and spent most of my time in a chair.

3.       By week 9, there was no improvement. I could walk fine but, I had the same pain when I tried to run. I visited the PA again and was put in a walking cast and had an MRI. The MRI should a low grade deltoid and ATFL sprain as well as a bruised bone. I spent 2 weeks in the walking cast then returned to the soft cast for another week. During this time I did nothing besides give it rest.

4.       At week 11, I did not see a noticeable improvement. I still had a sharp pain in my posterior tibial tendon area and deltoid area during the middle of my gait (when trying to run). At this time, I had another visit with the PA. After looking at my MRI more closely, he saw fluid buildup behind my talus. He thinks that I had an impact injury to my Os Trigonum. He also noticed that I had very limited dorsiflexion.  He has advised me to stretch and give it a few more weeks. If it’s not going in a positive direction he recommended a cortisone shot.

As it stands today at week 12, in a dorsiflexion position, I have a sharp pain in what feels like my Achilles tendon and posterior tibial tendon area (the MRI shows these are intact). I also have a lot of tenderness in the deltoid area. Walking, I am almost pain free but as soon as I begin to run, the pain starts in the areas described above. This is the first injury I have ever had where I haven’t seen a steady improvement when recovering (maybe I am just getting old). The pain I am having now when trying to running is the same as it was at week 4. This really concerns me.

I guess my question is, where do I go from here? Do I keep doing what I am doing? Should I seek a second opinion?  Any help or guidance you could provide would be greatly appreciated.

On a side note, your blog has helped me to get though the last 12 run-less weeks without losing my mind or falling into a deep depression.  You guys do some great stuff.  Keep up the good work!

Best Regards,

MR

____________________

Dear MR:

Somehow we missed this email. Sorry about that.

Whenever things are not resolving with reasonable intervention one must think of two things: either the injury was severe or the diagnosis is incorrect.

Without seeing you we are unable to determine either. But here are our thoughts.

The Os Trigonum syndrome is a good thought. It seems to be in the correct area of your complaint. These “Os” bones can be embedded in tendon or soft tissue and they can be fixed to the posterior talus by either bone or a cartilagenous bridge. It is possible for this to be your problem if the inversion event was severe enough although it is not that common in this described mechanism.

One must also be suspect of osseous compression of the medial talus against the medial calcaneus, which will bring thoughts of a posterior subtalar facet fracture. We pulled up an article we read a few years ago on this issue (click here), the article is entitled, “Pseudo os trigonum sign: missed posteromedial talar facet fracture”. Obviously this needs to be considered in your case since there are similar components in area and symptom of your complaints. Posteromedial talar facet fracture (PMTFF) is a rare injury, sparsely reported in the literature and it must be chased as a diagnosis of suspicion when all other clinical presentations have not panned out. Damage to the sustentaculum tali must also be assessed, as this too can be fractured.  Osteochondral defects are also always on the list in violent inversion events; they are classically seen anteromedially and posteriolaterally at the ankle mortise joint.

Something else that is often missed in ankle inversion sprains is avulsion or rupture of the extensor digitorum brevis on the lateral foot. As the rearfoot inverts and forefoot plantarflexes the EDB is tensioned to the point of tearing. Although you seem to have no symptoms in this area it can never be overlooked. These are easy to discern from the lateral ligamentous structure damage because the areas are clearly separate from eachother.  Look for tenderness down into the top of the metatarsals into the forefoot. Also test for weakness and pain of toe extension.

So, lots to consider here in this case. When things to not resolve you have to start looking for less common problems and damage.  We would love to hear how you are doing MR. Drop us a line.

Shawn and Ivo……. also geeks of orthopedics.  We paid the piper long ago.