Saturday, January 14, 2017

The Fascial Slings of the Foot and the Balance of the Arches, Part 1

Several authors have described a 'stirrup' or fascial sling of the foot which affects the balance of the arches.1,2 This sling comprises two or three muscles (depending on which author you're reading) which are linked through fascial connections at the medial arch of the foot. These are the tibialis anterior (which crosses the ankle to attach to the medial cuneiform and the base of the 1st metatarsal joint) and the peroneus longus (which crosses under the foot to attach to the same region). Sometimes, the tibialis posterior muscle is also included, as it has a large attachment area on the plantar region of the foot and interacts with the above two muscles.

In this post I will discuss the relationship of the tibialis anterior and tibialis posterior. These are part of the Stomach and Spleen sinew channels, respectively. They have a synergistic relationship, working together to lift the medial arch. In the next post I will follow up and discuss the relationship of the tibialis anterior and peroneus longus. These have an antagonist relationship, and balance between them is crucial for proper balance among the arches of the feet.

Fig.1

The tibialis anterior is part of the anterior crural (leg) compartment (Fig. 1). It attaches from the upper two thirds of the anterolateral tibia; crosses over the anterior ankle to the medial side and is held in place by the anterior ankle retinaculum; and then attaches to the medial cuneiform and base of the first metatarsal (Fig. 2). It performs dorsiflexion of the foot at the ankle, and it inverts the foot.

Fig. 2: Image from Gray's Anatomy
Fig. 3: Image from Atlas of Human Anatomy for Students and Physicians by Carl Toldt

The tibialis posterior is part of the deep posterior crural compartment (Fig. 1). It attaches to the inner border of the tibia, fibula and interosseus membrane. Initially, it is the middle muscle of the deep posterior compartment (Fig. 3), but it crosses under the flexor digitorum longus to become the most medial deep posterior compartment muscle at SP-6 (see this post about SP-6 three yin crossing). It is the most anterior tendon to pass behind the medial malleolus; it passes through the tarsal tunnel and then attaches to every tarsal bone except the talus, and it attaches to the 2nd, 3rd and 4th metatarsals (Fig.2)

Both of these muscles are important as they lift and support the medial arch. They can frequently become inhibited and fail to adequately support and lift the medial arch.

Fig. 4
Note the relationship of these two muscles in Fig. 4. The tibialis anterior is part of the Stomach sinew channel, whereas the tibialis posterior is part of the Spleen sinew channel.3 The muscles of these two sinew channels are much more synergistic than what is seen in more antagonist muscles found in other muscles of internal-external pairings.4,5

This synergistic nature is consistent with both the Spleen and Stomach primary channels and organs. Even the classical descriptions of these organs reflect this. It is worth remembering that in the description of the organs and their bureaucratic roles (which, for the classical physician, was a memory aid and a simple way to remember the functions of the organs), all of the organs had their own line in the Su Wen, with the exception of the Spleen and Stomach.

"The spleen-stomach holds the office of the granaries and issues the five flavors."6

The fact that these organs are discussed together reflects their synergistic nature in the body. I see that this is also reflected in the relationship between the sinew channels of these two networks. See the previous blog post about patellar balance of the Spleen and Stomach sinew channels for an exploration of how these channels work together to produce knee extension, but can be involved in imbalances which can affect patellar tracking.

For the foot, they work together to do what the Spleen and its related Stomach networks do; they lift. And, in this case, they lift the medial arch.3

Clinically, both of these muscles can fail to adequately lift and support the medial arch, especially in impact sports such as running. A certain amount of pronation is normal as weight is born by the foot; it acts as a shock absorber. This occurs with a medial rotation of the tibia and a drop of the navicular bone. Problems occur when there is foot overpronation, as the movement become excessive and added stress occurs in the soft tissue structures of the foot and leg, with biomechanical changes occurring in the the foot, ankle, knees, hips and throughout the body.7 Common injuries can include plantar fasciitis/fasciosis and anterior or medial shin splints (also referred to as tibialis anterior syndrome and tibialis posterior syndrome). But foot overpronation can also be a contributing factor for knee injuries and hip injuries, as this condition often correlates with excessive knee valgus (knees moving in with weight bearing) and excessive elevation of the ilium with weight bearing.

Local treatment involves specific local needling techniques to work with the fixed pain site .7,8 There will be different local techniques for plantar fasciitis, versus shin splints, versus something such as iliotibial band friction syndrome. Adjacent points can be selected to address the overactive and inhibited muscles; needling of the motor points can be used to address the foot overpronation or other imbalance of the foot.

There are cautions for needling the tibialis posterior. It can be accessed through the Spleen channel, but the depth it takes to reach the motor point takes the needle very close to the tibial artery, and instruction of this specific needle technique is best left to a classroom. SP-6, however, reaches and influences the tibialis posterior at the region that it crosses in front of the flexor digitorum longus and becomes the most medial (and most accessible) muscle of the deep posterior compartment.

Tibialis anterior, on the other hand, is simple, as its motor point is ST-36 (zusanli or leg three miles). Another motor point of tibialis anterior is the extrapoint lanweixue. The most reactive point can be selected for best results. I typically find ST-36 to be the most influential point to improve functionality of the tibialis anterior.

Additional treatment thoughts will be discussed in the next post after discussing the peroneal muscles and their role in injury.

References:

1. Myers, Thomas W. "The spiral line." Anatomy Trains: Myofascial Meridians for Manual and Movement Therapists. 3rd ed. Edinburgh: Churchill Livingstome, 2014. 132-149. Print.

2. Clemente, Carmine D. Anatomy: A Regional Atlas of the Human Body. Baltimore: Williams & Wilkins, 1997.

3. Lau, Brian. "Anatomy of the Sinew Channel: Lower Extremities." Module Four: The Lower Extremities Anatomy/Palpation/Cadaver Lab. Pacific College of Oriental Medicine, San Diego. 10 Sept. 2015. Lecture..

4. Lau, Brian, and Matt Callison. "Creating a Modern Model for the Assessment and Treatment of the Sinew Channels (Jingjin): Part 1." Oriental Medicine Newspaper (June 2016): 7; 33. Print.

5. Callison, Matt, and Brian Lau. "Anatomy of the Sinew Channels (Jingjin)." Pacific Symposium. Catamaran Resort Hotel, San Diego. 29 Oct. 2016. Lecture.

6. Wang, Ju-Yi, and Jason D. Robertson. "The tai yin (greater yin) system." Applied Channel Theory in Chinese Medicine: Wang Ju-Yi's Lectures on Channel Therapeutics. Seattle: Eastland Press, 2008. 64-76. Print.

7. Callison, Matt. An Acupuncturist's Guide to the Treatment and Assessment of Plantar Fasciitis and Excessive Foot PronationSports Medicine Acupuncture: Resources. Sports Medicine Acupuncture. Web.

8. Callison, Matt. "Acupuncture & Tibial Stress Syndrome (Shin Splints)." Journal of Chinese Medincine 70 (2002): n. pag. Web.

2 comments:

  1. I think I remember from the SW that Gb39 is for fallen arches...

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    1. I could see that being a useful point. GB 39, depending on where you locate it, could be on the peroneus tertius and/or extensor digitorum longus. Actually, peroneus tertius is an expansion of EDL. These muscle evert the foot and reducing this point would be useful for an overactive peroneus tertius and EDL and it would help reduce eversion.

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