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Adult Flatfoot
Posterior tibial tendon dysfunction is one of
several terms to describe a painful, progressive flatfoot deformity in
adults. Other terms include posterior tibial tendon insufficiency and
adult acquired flatfoot.
The term adult acquired flatfoot is more appropriate
because it allows a broader recognition of causative factors, not only
limited to the posterior tibial tendon, an event where the posterior
tibial tendon looses strength and function.
The adult acquired flatfoot is a progressive,
symptomatic (painful) deformity resulting from gradual stretch
(attenuation) of the tibialis posterior tendon as well as the ligaments
that support the arch of the foot.
Most flat feet are not painful, particularly those
flat feet seen in children. In the adult acquired flatfoot, pain occurs
because soft tissues (tendons and ligaments) have been torn. The
deformity progresses or worsens because once the vital ligaments and
posterior tibial tendon are lost, nothing can take their place to hold
up the arch of the foot.
The painful, progressive adult acquired flatfoot
affects women four times as frequently as men. It occurs in middle to
older age people with a mean age of 60 years. Most people who develop
the condition already have flat feet. A change occurs in one foot where
the arch begins to flatten more than before, with pain and swelling
developing on the inside of the ankle. Why this event occurs in some
people (female more than male) and only in one foot remains poorly
understood. Contributing factors increasing the risk of adult acquired
flatfoot are diabetes, hypertension, and obesity.
The following scheme of events is thought to cause the adult acquired flatfoot:
A person with flat feet has greater load placed on
the posterior tibial tendon which is the main tendon unit supporting up
the arch of the foot. Throughout life, aging leads to decreased
strength of muscles, tendons and ligaments. The blood supply diminishes
to tendons with aging as arteries narrow. Heavier, obese patients have
more weight on the arch and have greater narrowing of arteries due to
atherosclerosis. In some people, the posterior tibial tendon finally
gives out or tears. This is not a sudden event in most cases. Rather,
it is a slow, gradual stretching followed by inflammation and
degeneration of the tendon. Once the posterior tibial tendon stretches,
the ligaments of the arch stretch and tear. The bones of the arch then
move out of position with body weight pressing down from above. The
foot rotates inward at the ankle in a movement called pronation. The
arch appears collapsed, and the heel bone is tilted to the inside. The
deformity can progress until the foot literally dislocates outward from
under the ankle joint.
There are three stages of the adult acquired flatfoot:
| Stage I:
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Inflammation and swelling of the posterior tibial tendon around the inside of the ankle.
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| Stage II:
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Visible deformity comparing one foot to the other, as the symptomatic
foot becomes flatter and more deformed. The deformity is movable and
correctable in this stage. |
| Stage III:
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The foot progresses to a rigid, non-movable flat foot deformity that is painful, primarily on the outside of the ankle
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Diagnosis:
The adult acquired flatfoot, secondary to posterior
tibial tendon dysfunction, is diagnosed in a number of ways with no
single test proven to be totally reliable.
The most accurate diagnosis is made by a skilled
clinician utilizing observation and hands on evaluation of the foot and
ankle. Observation of the foot in a walking examination is most
reliable. The affected foot appears more pronated and deformed compared
to the unaffected foot. Muscle testing will show a strength deficit. An
easy test to perform in the office is the single foot raise.
A patient is asked to step with full body weight on
the symptomatic foot, keeping the unaffected foot off the ground. The
patient is then instructed to "raise up on the tip toes" of the
affected foot. If the posterior tibial tendon has been attenuated or
ruptured, the patient will be unable to lift the heel off the floor and
rise onto the toes. In less severe cases, the patient will be able to
rise on the toes, but the heel will not be noted to invert as it
normally does when we rise onto the toes.
X-rays can be helpful but are not diagnostic of the
adult acquired flatfoot. Both feet - the symptomatic and asymptomatic -
will demonstrate a flatfoot deformity on x-ray. Careful observation may
show a greater severity of deformity on the affected side.
Magnetic Resonance Imaging (MRI)
can show tendon injury and inflammation but cannot be relied on with
100% accuracy and confidence. The technique and skill of the
radiologist in properly positioning the foot with the MRI beam are
critical in demonstrating the sometimes obscure findings of tendon
injury around the ankle. Magnetic Resonance Imaging (MRI) is expensive
and is not necessary in most cases to diagnose posterior tibial tendon
injury. Ultrasound
has also been used in some cases to diagnose tendon injury, but this
test again is usually not required to make the initial diagnosis.
Treatment:
The adult acquired flatfoot is best treated early.
There is no recommended home treatment other than the general avoidance
of prolonged weightbearing in non-supportive footwear until the patient
can be seen in the office of the foot and ankle specialist.
In Stage I, the inflammation and tendon injury will
respond to rest, protected ambulation in a cast, as well as
anti-inflammatory therapy. Follow-up treatment with custom-molded foot orthoses
and properly designed athletic or orthopedic footwear are critical to
maintain stability of the foot and ankle after initial symptoms have
been calmed.
Once the tendon has been stretched, the foot will
become deformed and visibly rolled into a pronated position at the
ankle. Non-surgical treatment has a significantly lower chance of
success. Total immobilization in a cast or Camwalker may calm down
symptoms and arrest progression of the deformity in a smaller
percentage of patients. Usually, long-term use of a brace known as an
ankle foot orthosis is required to stop progression of the deformity
without surgery.
A new ankle foot orthosis known as the Richie Brace,
has proven to show significant success in treating Stage II posterior
tibial dysfunction and the adult acquired flatfoot. This is a
sport-style brace connected to a custom corrected foot orthotic device
that fits well into most forms of lace-up footwear, including athletic
shoes. The brace is light weight and far more cosmetically appealing
than the traditional ankle foot orthosis previously prescribed. Other
types of braces are the Arizona brace, the California brace or the
gauntlet brace. The decision on which type of brace to use is based
upon the patients overall needs.
In cases where cast immobilization, orthoses and
shoe therapy have failed, surgery is the next alternative. The goal of
surgery and non-surgical treatment is to eliminate pain, stop
progression of the deformity and improve mobility of the patient. These
surgical patients may be candidates for a 15 minute outpatient
procedure to correct the flexible flatfoot deformity which is referred
to as hyperpronation. The procedure is called a Subtalar Arthroereisis.
It involves the placement of an implant in the space under the ankle
joint (sinus tarsi) to prevent only the abnormal motion, but still
allowing normal motion. This brief procedure only requires very little
recovery time, and is completely reversible, if necessary. Your surgeon
can consult you about this exciting, life-changing procedure, or more
information can be obtained at www.hyperpronation.com.
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