Dr. Jeffrey A. Oster, DPM, C. Ped
Posterior tibial tendon dysfunction (PTTD), also known as
posterior tibial tendonitis, is one of the leading causes of
acquired flatfoot in adults. The onset of PTTD may be slow and
progressive or abrupt. An abrupt onset is typically linked to
some form of trauma, whether it be simple (stepping down off a
curb or ladder) or severe (falling from a height or automobile
accident). PTTD is seldom seen in children and increases in
frequency with age.
The characteristic finding of PTTD include;
Loss of medial arch height Edema (swelling) of the medial ankle
Loss of the ability to resist force to abduct or push the foot
out from the midline of the body Pain on the medial ankle with
weight bearing Inability to raise up on the toes without pain
Too many toes sign Lateral subtalar joint (outside of the ankle)
pain
A common test to evaluate PTTD is the 'too many toes sign'. The
'too many toes sign' is a test used to measure abduction
(deviation away from the midline of the body) of the forefoot.
With damage to the posterior tibial tendon, the forefoot will
abduct or move out in relationship to the rest of the foot. In
cases of PTTD, when the foot is viewed from behind, the toes
appear as 'too many' on the outside of the foot due to abduction
of the forefoot.
In advanced cases of PTTD, in addition to the pain of the tendon
itself, pain will also be noted at the sinus tarsi. The sinus
tarsi refers to a small tunnel or divot on the outside of the
ankle that can actually be felt. This tunnel is the entry to the
subtalar joint. The subtalar joint is the joint that controls
the side to side motion of the foot, motion that would occur
with uneven surfaces or sloped hills. As PTTD progresses and the
ability of the posterior tibial tendon to support the arch
becomes diminished, the arch will collapse overloading the
subtalar joint. As a result, there is increased pressure applied
to the joint surfaces of the lateral aspect of the subtalar
joint, resulting in pain.
There have been many proposed explanations for PTTD over the
years since this condition was first described by Kulkowski in
1936. The most contemporary explanation refers to an area of
hypovascularity (limited blood flow) in the tendon just below
the ankle. Tendon derives most of its' nutritional support from
synovial fluid produced by the outer lining of the tendon.
Extremely small blood vessels also permeate the tendon sheath to
reach tendon. This makes all tendon notoriously slow to heal. In
the case of the posterior tibial tendon, this problem is
exacerbated by a distinct area of poor blood flow
(hypovascularity). This area is located in the posterior tibial
tendon just below or distal to the inside ankle bone (medial
malleolus).
Tendon is also most susceptible to fatigue and failure at an
area where the tendon changes direction. As the posterior tibial
tendon descends the leg and comes to the inside of the ankle,
the tendon follows a well defined groove in the back of the
tibia (bone of the inside of the ankle). The tendon then takes a
dramatic turn towards the arch of the foot. If the tendon is put
into a situation where significant load is applied to the foot,
the tendon responds by pulling up as the load of the body (in
addition to gravity) pushes down. At the location where the
tendon changes course, the tibia acts as a wedge and may apply
enough force to actually damage or rupture the tendon.
Equinus is also a contributing factor to PTTD. Equinus is the
term used to describe the ability or lack of ability to
dorsiflex the foot at the ankle (move the toes toward you).
Equinus is usually due to tightness in the calf muscle, also
known as the gastroc-soleal complex (a combination of the
gastrocnemius and soleus muscles). Equinus may also be due to a
bony block in the front of the ankle. The presence of equinus
forces the posterior tibial tendon to accept additional load
during gait.
Additional contributing factor to the onset of PTTD may include
hypertension, diabetes, peripheral neuropathy, smoking or
arthritis.
The progression of PTTD may result in tendonitis, partial tears
of the tendon or complete tendon rupture. Several
classifications have been developed to describe PTTD. The
classification as described by Johnson and Strom is most
commonly used today.
Stage I Tendon status Attenuated (lengthened) with tendonitis
but no rupture Clinical findings Palpable pain in the medial
arch. Foot is supple, flexible with too many toes sign X-ray/MRI
Mild to moderate tenosynovitis on MRI, no X-ray changes
Stage II Tendon status Attenuated with possible partial or
complete rupture Clinical findings Pain in arch. Unable to raise
on toes. Too many toes sign present X-ray/MRI notes tear in
tendon. X-ray noting abduction of forefoot, collapse of
talo-navicular joint
Stage III Tendon status Severe degeneration with likely rupture
Clinical findings Rigid flatfoot with inability to raise up on
toes X-ray/MRI shows tear in tendon. X-ray noting abduction of
forefoot, collapse of talo-navicular joint
An additional consideration in planning for PTTD surgery and
diagnosing PTTD pain is the presence of an accessory bone called
an os tibiale externum. The os tibiale externum, or what is
frequently called and accessory navicular, is a small bone that
resides within the body of the PT tendon. The os tibiale
externum functions to facilitate motion around the navicular.
The os tibiale externum functions much in the same way that the
knee cap (patella) works to guide the quadraceps tendon around
the knee as it bends. The os tibiale externum can undergo
degenerative wear called chondromalacia. The os tibiale
externum also can fracture. Therefore, the os tibiale externum
must also be considered when diagnosing PT tendon pain and
planning surgery for PTTD. Excision of the os tibiale externum
during PT tendon correction is common.
Treatment of posterior tibial tendon dysfunction and posterior
tibial tendonitis
Treatment for PTTD is dependant upon the clinical stage and the
health status of the patient. It is important to recognize that
PTTD is a mechanical problem that requires a mechanical
solution. This means that treating PTTD with medication alone is
fraught with failure. Timely introduction of some form of
mechanical support is imperative.
Surgical procedures which focus on primary repair of the
posterior tibial tendon have been very unsuccessful. This is due
to the fact that tendon heals slowly following injury and cannot
be relied upon as a sole solution for PTTD cases. Surgical
success is usually achieved by stabilization of the rearfoot
(subtalar joint) which significantly reduces the work performed
by the posterior tibial tendon.
Stage I may respond to rest, such as a walking cast. Pain and
inflammation may be controlled with anti-inflammatory
medications. It is important to be sure that Stage I patients
realize that the use of shoes with additional arch support and
heel elevation, for the rest of their lives, is imperative. Arch
support, whether built into the shoe or added as an orthotic,
helps support the posterior tibial tendon and decrease its'
work. Elevation of the heel, reduces equinus, one of the most
significant contributing factors to PTTD. If Stage I patients
return to low heels without arch support, PTTD will recur.
Stage II patients, or Stage I patients that do not respond to
rest and support, require surgical correction to stabilize the
subtalar joint prior to further damage to the posterior tibial
tendon. Subtalar arthroeresis is a procedure used to stabilize
the subtalar joint. Arthroeresis is a term that means the motion
of the joint is blocked without fusion. Subtalar arthroeresis
can only be used in cases of Stage I or II where mild to
moderate deformation of the arch has occurred and MRI findings
show the tendon to be only partially ruptured. Subtalar
arthroeresis is typically performed in conjunction with an
Achilles tendon lengthening procedure to correct equinus. These
procedures require casting for a period of weeks following the
procedure.
Stage III patients require stabilization of the rearfoot with
procedures that fuse the primary joints of the arch and foot.
These procedures are salvage procedures and require prolonged
casting and disability following surgery. A common procedure for
Stage III is called triple arthrodesis which is a technique used
to fuse the subtalar joint, the talo-navicular joint and the
calcaneal cuboid joint.
PTTD is a condition that increases in frequency with age and the
prevalence of poor health indicators such as diabetes and
obesity. As a result, many patients with PTTD are poor surgical
candidates for correction of PTTD. Prosthetics such as an ankle
foot orthotic (AFO), AirLift Brace or other bracing may be very
helpful to control the symptoms of PTTD.
This article was written by Jeffrey A. Oster, DPM, medical
directory of Myfootshop.com.
About the author:
Dr. Jeffrey A. Oster is a Board Certified Podiatrist and Medical
Director of www.Myfootshop.com.