Anatomy and Technique      

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Abductor Hallucis  

By Doug Alexander

Overview  

The abductor hallucis is a significant, but seldom treated muscle located on the medial side of the foot. It can be strained from excessive standing postures, foot pronation and overload.

Trigger points in the abductor hallucis cause heel pain. Compression of the tibial nerve by the abductor hallucis can give aching in the foot as well as tingling and numbness. Tibial nerve compression by the abductor hallucis may also affect the health of the entire sciatic nerve, predisposing clients to sciatica and/or increasing the intensity of sciatica as well as increasing recovery time.

Anatomy 

Origin: The abductor hallucis originates from the medial process of the tuberosity of the clacaneus, the flexor retinaculum of the ankle, plantar aponeurosis and to an intermuscular septum between it and flexor digitorum brevis (Travell, page 504)

Insertion: Four fifths of the time, the tendon of abductor hallucis attaches to the plantar surface of the proximal phalange of the big toe. One fifth of the time it attaches to the medial side of the base of the proximal phalange.

Action: The abductor hallucis is predominantly a flexor of the big toe. When it attaches to the medial side of the proximal phalange it will also be capable of fulfilling its name, by abducting the big toe. The abductor hallucis also serves to stabilize the arches of the foot and provide some shock absorption and adaptability to walking on uneven surfaces.

Signs and Symptoms of Dysfunction  

Trigger points in the abductor hallucis cause an ache along the medial side of the heel and often a lesser ache along the inside of the instep (Travell, 504)

Aching might arise from a true trigger point referral situation or from compression of the sheath of the tibial nerve and its two branches the medial and lateral plantar nerves.

Compression of the nerve under the flexor retinaculum may cause tingling and/or numbness behind the ankle and in the sole of the foot.

Clients with sciatic nerve irritation may have a contribution to the irritability of the nerve as a result of abductor hallucis tension and/or strain (Butler 1991)

Dorsiflexion Eversion Test   

It is important to get a clear idea of the sensitivity of the tibial nerve in the tarsal tunnel when working with the abductor hallucis.

Koshita and colleagues developed a test for compression and/or irritation of the tibial nerve in the tarsal tunnel through working with a variety of clients with tarsal tunnel symptoms. The basis of the test is to dorsfilex all the toes (especially the big toe) and the ankle. This draws the flexor hallucis longus further into the tunnel it shares with the tibial nerve. This puts more compression on the nerve.

The other component of the test is to evert the foot at the ankle. This sensitizing movement tensions the flexor retinaculum overlying the nerve and further ads to compression.

The test posture is held for several seconds. Koshita found that this reliably recreates tarsal tunnel symptoms of burning, tingling, numbness or pain at the medial ankle and or sole of foot. It is not thought to create symptoms in client without tarsal tunnel problems.

The test also further sensitizes clients to Tinel’s sign at the entrance to the tarsal tunnel.

Framing Treatment

You may be drawn to treating a client’s abductor hallucis simply on the basis of feeling a more taut or dense tissue texture in the myofascia of the abductor hallucis. If the client has medial heel pain, excessive pronation or foot symptoms of strain and/or tingling/numbness or burning then you may also be drawn to treating the abductor hallucis.

If you sense that the abductor hallucis may be an issue, then it would be a good idea to perform the dorsiflexion evervsion test to determine the sensitivity of the tibial nerve. If the nerve is irritable (if symptoms are easily created that don’t abate as soon as you release the test) then you may need to milk fluid from the tarsal tunnel before treating the abductor hallucis. Additionally, you ought to be careful to avoid irritating the nerves below the abductor hallucis when initially treating it.

If the nerve is not irritable, or becomes less irritable with treatment, then your abductor halucis techniques can safely become more challenging including cross fiber manipulations and stripping along the entire length of the muscle.

If the abductor hallucis continues to be overloaded and causing problems, you may need to treat other muscles that help support the arch (tibialis posterior and tibialis anterior) as well as strengthen the arch, sometimes resorting to orthotic support as well.

Let’s look at each of these interventions in detail.

Treatment Techniques for the Abductor Hallucis   

Dropping the Resting Tone of the Abductor Hallucis

Treatment of the Abductor Hallucis needs to take the underlying neural tissue into consideration.

For this reason I often begin with strumming the muscle just distal to it’s origin on the calcaneus. This allows me to drop the tone in the muscle without compressing the tibial nerve or its branches which are just a little more distal to this point.

Then I treat the muscle just past the course of the nerve with the same techniques. As the muscle begins to relax and drop its tone, then the big toe can be dorsiflexed to consolidate the drop in tone with a bit of stretching to the muscle.

 Decompressing the Tibial and Plantar Nerves

After the tone has dropped in the abductor hallucis and a bit of length has been obtained in it, it is usually possible to decompress the tibial and plantar nerves. This can be done by stripping along their pathway, thereby loosening and lightening the myofascial roof that overlies them. This image at right with the dotted line shows the path that surgeons take when they decompress the tarsal tunnel with their scalpel.

Take the same path (gently!) with your finger or thumb as you release, soften, broaden and deepen the myofascial groove that the tibial and plantar nerves travel in through this region.

The general guideline is that the treatment techniques should not cause any increase in symptoms that lasts for more than a second after the technique is discontinued.

If you cannot perform this manipulation without making symptoms worse or last for more than a second after you stop the technique you must do something less challenging! This might mean milking the fluid from around the nerve, applying cold hydrotherapy or treating related, but less irritable structures.

If this doesn’t work, then you will have to refer your client to a more experienced therapist or their physician.

Stripping and Stretching the Abductor Hallucis  

After the tibial nerve and its branches are decompressed, the abductor hallucis is available for stripping manipulations. These run from the origin on the calcaneus and flexor retinaculum all the way out to the insertion(s) on the base of the proximal phalange.

 Treatment of the Tibial Nerve

There are a number of techniques that can be helpful when the tibial and/or plantar nerves are irritable.

Fluid Dynamic Techniques  

The first fluid dynamic technique is to milk fluid from the tarsal tunnel. Make sure that you have a soft contact over the region of the tarsal tunnel with your thenar and hypothenar eminences straddling the flexor retinaculum. Compress just the skin and superficial fascia and let the tissue recoil back into your hands. Continue this rhythmical fluctuation of fluid pressures for several minutes and you will gradually notice that deeper tissue begins to fluctuate. Keep this technique going until you feel that you have reached the level of the nerve (just over the bone) and that you have good fluid flow there.

 Joint Mobilizations

You can also fluctuate fluid pressures beginning deep in the joints of the ankle and working your way toward the overlying tendons and nerves. Grasp the calcaneus and the mid-foot and introduce a longitudinal distracting force along the long axis of the tibia (away from the hip). Just pull on the heel and foot until the point at which the ankle begins to resist you (this is usually about 1 millimeter of movement or about a couple ounces of force). Then, let the foot recoil toward the ankle and repeat. Continue this rhythmic distraction/recoil for several minutes until you feel a substantial increase in elasticity and play in the region.

Retinacular Release  

If there is still compression of the tibial nerve at this point, you may need to release the flexor retinaculum which overlies it. Begin your manipulations on the calcaneus attachments (this is distal to the tibial nerve and shouldn’t irritate it. After you have gotten some release, try releasing the retinaculum just below and posterior to the medial malleolus. When the retinaculum has been released from both attachments, it is usually available for longitudinal stretching manipulations from attachment to attachment without irritating the tibial nerve.

 Arch Supportive Interventions

If the abductor hallucis responds well to treatment, but tension, strain and dysfunction keep returning, one often needs to address related issues.

Weakness, strain and falling of the arches can chronically overload abductor hallucis.

The tibialis posterior and tibialis anterior support the medial longitudinal arch of the foot. In order to access the tibialis posterior (which originates from the back of the interosseous membrane between the tibia and fibula) on usually has to release the gastrocnemius and soleus muscles. This is a good idea anyways, since shortness in one or both of these muscles tends to put more strain on the plantar fascia. This is because part of the Achilles tendon continues on past it’s attachment on the calcaneus to blend in distally with the plantar aponeurosis. Tightness of the gastrosoleus complex can then place too much stress on the plantar aponeurosis and hence the arch.

After treating the gastrocnemius and soleus, the Achilles tendon should be stretched without placing any tension on the plantar fascia. This is done with the heel drag stretch. In this maneuver, you grasp the calcaneus and drag it distally and then put a gentle force on the foot toward dorsiflexion.

 The other muscle that frequently needs addressing is the tibialis anterior at the front of the shin. When it is overloaded and harbours myofascial trigger points it tends to do a poor job of supporting the arch. Ischemic compression, myofascial stripping and stretching to the tibialis anterior often helps it do its job better.

Short Foot Exercise  

If all of this manual therapy isn’t enough, the client will often need to strengthen the arches of the foot with the short foot exercise. They form the arch of the foot by actively dorsiflexing the big toe. Then they let the big toe relax and maintain the arch with their shin and calf muscles. They should be able to wiggle their toes and not have it influence the arch. Many people can only  do this when sitting at a chair because their arches have become so weak and deconditioned. However, with steady practice many people restore substantial strength in their arches again and symptoms subside.

If the short foot exercise isn’t enough to help the person, or is too difficult to perform, they may need a change in footwear, sometimes including orthotics. Keep this possible referral issue in mind!

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1. Abductor Hallucis Palpation
2. Tibial Nerve Palpation
3. Abductor Hallucis Symptoms
4. Dorsiflexion Eversion Test
5. Abductor Hallucis Treatment
6. Tibial Nerve Treatment
7. Arch Supportive Care

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References

Butler DS: Mobilisation of the Nervous System. London: Churchill Livingstone;1995.

Kinoshita M, Okuda R, et. Al.: The Dorsiflexion-Eversion Test for Diagnosis of Tarsal Tunnel Syndrome. The Journal of Bone and Joint Surgery 2001;83-A(12):1835-1839.

Travell JG, Simons DG: Myofascial Pain and Dysfunction: The Trigger Point Manual: Volume 2: The Lower Extremities. Baltimore: Williams and Wilkins;1992.