Power of Splay: New and improved

This time with some anatomy pix.

Think about triangles. Hey Pythaogoras did! They are powerful distributors of force. Here we will talk about 3 of them.

There are 4 layers of muscles in the foot. The 1st triangle occurs in the 1st layer. Think of the abductor hallucis and the abductor digiti minimi. Proximally they both attach to the calcaneus and distally to the 1st and 5th proximal phalanges. Now think about the transverse metatarsal ligament that runs between the disal metatarsal heads. Wow, a triangle! this one is superficial.

Now think about the adductor hallicus. It has a transverse and oblique head. think about that transverse metatarsal ligament again. Wow, another triangle!

What about the flexor hallicus brevis and flexor digiti minimi? The former originates from the cuboid, lateral cunieform andd portion of the tib posterior tendon; the latter from the proximal 5th metatarsal. They both go forward and insert into the respective proximal phalynx (with the sesamoids intervening in the case of the FHB). and what connects these? The deep transverse metatarsal ligament of course! And this triangle surrounds the adductor triangle, with both occurring the 3rd layer of the 4 layers of foot muscles.

Triangles… and you thought geometry was boring!

Remaining triangular when we need to (because of our pointy heads)…Ivo and Shawn

The Power of Splay

Watch the awesome power of the dorsal interossei and their importance in maintenance of the transverse metatarsal arch (Thanks to Runblogger for this clip)

Look to the next post for some pictures and an explanation!

Ivo and Shawn

 Splay

Watch this video a few times through. Did you catch the subtle abduction moment of the Hallux (big toe) on impact? Did you see the collapse of the transverse metatarsal arch? No?  Watch it until you do.

What gives? We thought toes were supposed to be stable when they hit the ground (and in fact they are).  Read on…

Think of the adductor hallucis. It has 2 heads. The oblique head arises from the proximal shafts of metatarsals 2-4 and inserts on the MEDIAL aspect of the proximal phalynx of the hallux (along with medial fibers of the flexor hallucis brevis); the transverse head arises from the metatarsophalangeal ligaments of  digits 3-5, and the transverse metatarsal ligament and inserts blending with the oblique head on the proximal phalynx of the hallux.

The action of the adductor hallucis mirrors that of the abductor hallucis (which inserts on the LATERAL side of the proximal phalynx. Together, they act to keep the hallux straight and provide a compressive force which stabilizes the big toe WHEN IT IS ON THE GROUND.

The problem here, is that the base of the Hallux is NOT anchored to the ground. This person has a faulty tripod (most likely an uncompensated forefoot varus) and cannot anchor the big toe, there fore the adductor cannot do it’s job. Is is weak (from lack of use) and we see the result: an abducting big toe AND collapse of the transverse metatarsal arch (which the transverse head of the adductor, under normal conditions maintains).

Looks like this guy needs some exercises to descend the head of the 1st metatarsal and make an adequate tripod. Flexing the distal phalynx of the hallux while extending the metatarsophalangeal joint would be a good start. (see Dr Allen demonstrate this here: http://www.youtube.com/user/TheGaitGuys?feature=grec_index#p/u/11/TyRE9dReVTE )

The Gait Guys…promoting foot literacy here and everywhere.