Posterior Tibial Tendon Dysfunction - PTTD
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.
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
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
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.
Short note about the author
Dr. Jeffrey A. Oster, DPM C.Ped
Dr. Jeffrey A. Oster is a Board Certified Podiatrist, and Medical Director of www.Myfootshop.com.
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