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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!
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.
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