Get your foot in High Gear!

image source: Foot Orthoses and Other Conservative Forms of Foot Care. Michaud 1997; Williams an Wilkins: with permission

When it comes to gait, getting the 1st ray to the ground is the name of the game. When weight travels through the medial forefoot and we are able to push off the 1st ray complex, that is called "high gear push off". This was 1st discussed F Bojsen-Møller in this excellent paper (1), that just happens to be a free full text! Craig Payne, The Running Research Junkie has offered and excellent commentary on the topic here as well.

High Gear Push Off can happen when 3 conditions are met: 

1. we have a intact visual, vestibular and kinesthetic systems that ensure we can remain upright in the gravitational plane.
2. we have an intact calcanocuboid locking mechanism
3. we have adequate skill, endurance and strength of our extensor hallucis brevis

The 1st condition is more global and ensures that our cerebellum and vestibular apparatus are playing nice together to create balance, of the literal sort, We seek to keep our visual axes parallel and our center of gravity over our foot. Remember that the BODY will move itself AROUND the visual axes. If the axes are off, the brain will tilt the head and the body will move AROUND the head to accommodate. We have talked about that in these posts here on the blog. 

The 2nd condition, the calcaneo-cuboid locking mechanism, works in the coronal plane and relies on a functioning peroneal group, where the peroneus longus and brevis wrap around the lateral malleolus, cuboid and tail of the 5th metatarsal, crossing the foot diagonally to insert on the base of the 1st metatarsal. When working properly, its actions will be to plantar flex and everting the forefoot, lowering the 1st ray complex down and assisting the shift of the center of gravity more medial for the weight to pass through the medial foot and out through the hallux (ideally). 

The 3rd condition, the ability to descend the 1st ray, relies on the actions of the peroneus, appropriate supination of the forefoot and ability of the extensor hallucis brevis to do its job.  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, 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). If the axis of motion for the 1st metatarsal phalangeal joint moves posteriorly, to behind (rather than under) the joint, the plantar pressures increase at MTP’s 4-5 and decrease at the medial mid foot, moving you into low gear push off.  If moved even further posteriorly, the plantar pressures, and contact time in the mid foot and hind foot (2). For more on the extensor hallucis brevis, see our post here.

As you can see, high gear is desirable over low gear push off, but sometimes circumstances or biomechanics do not permit. High gear push off ensures the forefoot is dorsiflexed and everted with respect to the rearfoot and the calcaneocuboid and talonavicular joint axes are perpendicular to one another, giving us a rigid lever to push off of as the center of gravity moves medially across the foot. In low gear push off, the foot is inverted and plantarflexed and the stress falls on the lesser metatarsals and lateral stabilizing complex of the ankle, moving the center of gravity laterally, in addition to the calcaneocuboid and subtalar joint axes being more parallel,  creating a less rigid lever for push off and decreased mechanical efficiency.

1. Calcaneocuboid joint and stability of the longitudinal arch of the foot at high and low gear push off. J Anat. 1979 Aug; 129(Pt 1): 165–176.  link to free full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1233091/

2. van der Zwaard BC1, Vanwanseele B, Holtkamp F, van der Horst HE, Elders PJ, Menz HB Variation in the location of the shoe sole flexion point influences plantar loading patterns during gait. J Foot Ankle Res. 2014 Mar 19;7(1):20.

The Power of the 1st Ray?

Does the 1st ray complex have super powers? Perhaps Marvel should consider a new superhero “Ray”? We are not sure but here is a story that gets us one step closer to the answer. 

While teaching a course this past weekend and doing a teaching case, we examined one of the participants who had high arches, a rigid rearfoot varus, internal tibial torsion, R > L, and foot pain R>L and a dorsal exostosis (growth of extra bone from stress at the base of her 1st metatarsal) where it articulated with the  1st cunieform on the right. No surprisingly, she also had a partially compensated forefoot supinatus on the right. She had increased wear on the lateral aspect of her shoes and a walking strategy which involved hiking the right side of the pelvis during stance phase on the left, and a pelvic shift to the right during stance phase on the right, as well as an inability to get the head of either 1st ray complex to the ground, R > L. It was also determined she had, not surprisingly, locking of the 1st metatarsal cunieform joint on the right and a loss of anterior and posterior shear at the superior tib fib articulation on the right, as well as hypomobility of the right sacoiliac joint. There was weakness of the abdominal external obliques bilaterally and posterior fibers of the left gluteus medius, along with the long toe extensors on the left and short toe flexors, a pattern that we often see clinically.

We then proceeded to treat her tib posterior, peroneus longus and flexor digitorum on the right, all of which have an effect on descending the 1st ray, along with the long extensors on the right, which would effectively raise the distal aspect of the 1st ray, but we thought may provide better eccentric control of the foot from initial contact to loading response, and again from the end of terminal stance and through swing phase.  We then mobilized the 1st met cunieform articulation only. Ideally, we should have reassessed after we made EACH change, but due to time constraints, AFTER we had done ALL these things. 

Rexamination had better 1st ray motion, restoration of tib fib motion and restoration of R sided SI mechanics. Her 1st ray descended much better, tib fib motion was normalized, L sided hip hiking strategy and R sided pelvic shift were greatly improved. For the 1st time in 10 years, the participant had no foot pain. Coincidence? Perhaps. Placebo? Maybe. You decide. 

Sometimes, doing a little of the right thing can be a good thing. Sometimes we overdo. I have to admit, because I am a chiropractor, I would have started with manipulation 1st of all 3 articulations with a recheck immediately post treatment AND THEN treated the other dysfunctions. For those of you who are manual therapists, I am sure you see miraculous things happen when we cavitate joints and change their instantaneous axes of rotation. I can thank Dr Ted Carrick and my good friend and colleague, Dr Paul Chille, for teaching me that. The students, in this case, were driving the bus and I went along with it.  I was surprised (though I shouldn’t have been) to see the pathomechanics resolve WITHOUT manipulation, but it got me thinking I should consider treating the muscular dysfunctions 1st, and then recheck and manipulate later. It makes sense that the receptor density of the lower extremity musculature has a much larger population of muscle mechanoreceptors, especially in the foot, since it has a greater cortical representation than the joint mechanoreceptors.

My students never cease to teach me something new...

The EHB....In all its glory...

The extensor hallucis brevis : An overlooked "miracle worker"

The Extensor Hallicus Brevis, or EHB as we fondly call it 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 (1).

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 (2-4).

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).

Why is this so important?

The central axis of a joint (sometimes called the instantaneous axis of motion) is the center of movement of that articulation. It is the location where the motion will occur around, much like the center of a wheel, where the axle attaches. In an articulation, it usually involves one bone moving around another. Lets look at an example with a door hinge.

A hinge is similar to a joint, in that it has parts with is joining together (the door and the jamb), with a “joint” in between, The axis of rotation of the hinge is at the pivot rod. When the door, hinge and jamb are all aligned, it functions smoothly. Now imagine that the hinge was attached to the jamb 1/4” off center. What would happen? The hinge would bind and the door would not operate smoothly.

Now let’s think about the 1st metatarsal phalangeal joint. It exists between the head of the 1st metatarsal and the proximal part of the proximal part of the proximal phalanyx. Normally, because the head of the 1st metatarsal is larger than the heads of the lesser ones, the center of the joint is higher (actually,almost 2X as high; 8mm as opposed to 15mm). We also remember that the 1st metatarsal is usually shorter then the 2nd, meaning during a gait cycle, it bears the brunt of the weight and hits the ground earlier than the head of the 2nd.

The head of the 1st metatarsal should slide (or should we say glide?) posteriorly on the sesamoids during dorsiflexion of the hallux at pre swing (toe off). It is able to do this because of the descent of the head of the 1st metatarsal, which causes a dorsal posterior shift of the axis of rotation of the joint. We remember that the head of the 1st descends through the conjoined efforts of supination and the coordinated efforts of the peroneus longus, extensor hallucis brevis, extensor hallucis longus, dorsal and plantar interossei and flexor hallucis brevis (which nicely moves the sesamoids and keeps the process going smoothly)(1, 5).

Suffice it to say, if things go awry, the axis does not shift, the sesamoids do not move, and the phalanyx crashes into the 1st metatarsal, causing pain and if it continues, a nice spur you can write home about!

Treating and needling this muscle is easy, as it is very accessible on the dorsum of the foot and due to the decreased receptor density, is not too uncomfortable. We like to needle the peroneus longus and short flexors as well, as they all have the function of lowering the head of the 1st ray. Check it out in this quick how to video.

1. Michaud T: Human Locomotion: The Conservative Management of Gait Related DisordersNewton Biomechanics; First Edition 2011

2. https://www.physio-pedia.com/Extensor_Hallucis_brevis

3. http://www.wheelessonline.com/ortho/extensor_hallucis_brevis

4. Becerro de Bengoa Vallejo R., Losa Iglesias M.E., Jules K.T.  Tendon Insertion at the Base of the Proximal Phalanx of the Hallux: Surgical Implications (2012)  Journal of Foot and Ankle Surgery,  51  (6) , pp. 729-733.

5. Zelik, K.E., La Scaleia, V., Ivanenko, Y.P. et al. Eur J Appl Physiol (2015) 115: 691. https://doi.org/10.1007/s00421-014-3056-x

1st met pain in an orthotic?

This patient came in with pain at the base of the first metatarsal that she believed was related to her orthotic. The first picture shows the foots relationship to the orthotic. Notice how the sesamoid bones and distal aspect of the first metatarsal under lap the orthotic shell. In other words, the shell is longer than her foot. When she dorsiflexes her big toe, she’s hitting the distal of the orthotic.

The next view shows the orthotic with a typical first ray cutout. Notice how far forward the shell of the orthotic goes (next picture). I have placed a pen pointing to the area where the orthotic shell is too long.

In addition to reviewing her first ray descending exercises, a simple fix was to grind back the orthotic shell and be careful to bevel the edge so that it was not hitting the sesamoids and it did not impinge upon the descending first ray. I have placed a pen where the cut out now is (pre and post gluing in the pictures). The cork underlying the base of the first ray was also ground away (last picture)

A simple fix for a common problem. Make sure that your orthotic shell lengths fall just short of the 1st ray and not impinge on the sesamoids!

One way to correct an dysfunctional Extensor Hallucis Brevis

The Extensor Hallicus Brevis, or EHB  (beautifully pictured above causing the  extension (dorsiflexion) of the proximal big to 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.

Since this muscle is frequently dysfunctional, and is one of THE muscles than can lower the head of the 1st metatarsal, along with the peroneus longus and most likely the tibialis posterior (through its attachment to the 1st or medial cunieform), needling can often assist in normalizing function and works especially well, when coupled with an appropriate rehab program. Here is one way to needle it effectively. 

1st MTP Pain?

It may not be a trigger point. In this capsule summary, Dr Ivo discusses an interesting and perhaps revolutionary, theory on trigger point pain that refers to the 1st metatarsal phalangeal articulation. The anatomy of the joint and responsible muscles are also discussed