Ill-Effects of HyperPronation to the Soft Tissues of the FootMichael E. Graham, DPM, FACFAS
Starting at the foundation of the body, when there is abnormal closure of the sinus tarsi resulting in excessive talar motion excessive abnormal forces are placed on the various soft tissue structures on the inner aspect of the foot and ankle. Specifically, these include the posterior tibial tendon, plantar fascia, and the tarsal tunnel. Remember that the less than average person takes a minimum of 10,000 steps a day. There is already a lot of force placed on these soft tissues. Now that they are being excessively overstretched with every step taken, eventually symptoms that something is wrong will begin.
The posterior tibial tendon is a very strong structure that helps to lift the foot when walking. Walking is the second most common thing we do beside breathing. So with every step this tendon's job is to lift the foot for the next step. A tendon is made up of thousands of long fibers and is connected from the muscle and inserts into the bone. This tendon with a hyperpronating foot is overstretched with every single step. The overstretching eventually results in micro ruptures of the tendon leading to tendonitis. Pain begins and the patient will usually limit their walking and the pain will subside. Meanwhile, the underlying deformity is still present, so they will resume the activity and the pain comes back. So they go for treatment including oral medications, injections, physical therapy, strapping of the ankle, and possibly "corrective" inserts for their shoes. Unfortunately, the obliteration of the sinus tarsi is still occurring with every step taken. It is possible that the mirco ruptures will heal and the patient will no longer require the treatments. So they get up the courage to resume their activities without the symptoms but this will only last for a short period of time.
What has happened is, let's say your car tire was not properly balanced. Initially, you don't notice the difference, but the more you drive with an unbalanced tire abnormal forces are placed on it resulting in excessive wear and tear which further leads to excessive motion of the tire. Eventually, the tires will wear out and even go flat. So the car is then taken back to the car shop and another unbalanced tire is placed on the car. Again, initially, there is an improvement but just like before it is a matter of time before that tire is also worn out.
A foot with posterior tibial dysfunction would best be treated with a sinus tarsi implant to prevent this abnormal closure of the sinus tarsi. This would result in the restoration of normal mechanics and the excessive strain placed on the posterior tibial tendon would be eliminated. The micro ruptures would be allowed to heal and the previous methods of treatment would now be more effective.
The plantar fascia (pronounced- fa-she-a)is a very thick ligament-like structure on the bottom of the foot. The function of the plantar fascia is to give a "spring" to the foot. It starts at the bottom of the heel and extends to the ends of the metatarsal bones. When normal mechanics occur in the foot, the plantar fascia functions as it is supposed to, no problem. However, when there is obliteration of the sinus tarsi leading to excessive motion of the talus on the calcaneus overstretching of the plantar fascia occurs. The heel bone (calcaneus) will try to compensate for this overstretching of the plantar fascia. Since this ligament-like structure is pulling abnormally on the bone it actually pulls on the outer covering of the bone, called the periosteium. This will result in the formation of extra shelf of bone on the bottom front portion of the heel commonly known as a "heel spur". A heel spur is a very common finding on x-rays, the majority of people with these have never had pain in their heel. The reason why is that the heel was able to grow enough bone that it compensated for the excessive stretch of the plantar fascia. But, if the heel is not able to form this bone extension fast enough another condition will result called plantar fasciitis (fa-she-i-tis). This is an inflammation of the plantar fascia, actually it is the results of micro ruptures of the small fibers that make up this structure. Just like the tendon, the more walking/running a person does with hyperpronation abnormal excessive forces are placed on the ligament and it will eventually rupture.
The pain is worse in the morning when the patient gets out of bed. The reason for this pain is that during the day the plantar fascia is overstretched. Then during the night the fascia contracts, and when the patient starts to walk again the fascia will be overstretched again. This vicious cycle continues until more and more of the fibers rupture. Usual treatment consists of oral anti-inflammatory medications, injections, taping, ice, "corrective" inserts, physical therapy, shock-wave, etc. Just like the posterior tendon, eventually, the inflammation will subside and the fascia will heal or the fibers will continue to rupture on their own acting like a lengthening procedure. Meanwhile, the underlying deformity is present and eventually the same problem will occur. So the best treatment for this condition is to prevent the abnormal closure of the sinus tarsi with a sinus tarsi implant. This will immediately eliminate the excessive forces on the plantar fascia. With the implant in place, the previously mentioned treatment modalities will be effective.
Tarsal tunnel syndrome is the result of chronic overstretching of the inner soft tissue structures behind the inner ankle bone (medial malleolus). This a very over-looked or ignored condition. A common symptom with this condition is a tingling/numbness or strange feeling to the toes and ball of the foot. Most of us are aware of a condition of the hand called carpal tunnel syndrome. This results in a numbness and tingling sensation to the fingers and is caused by compression of a nerve in the wrist. Likewise, tarsal tunnel syndrome is caused by chronic irritation to the posterior tibial nerve located in the tarsal tunnel. The tarsal tunnel is a tunnel that starts above the inner ankle bone and extends into the bottom of the foot. The main artery, vein, and nerve to the bottom of the foot are located within this anatomical space.
When there is excessive inward motion of the talus due to the obliteration of the sinus tarsi, this leads to overstretching of the soft tissues behind the inner ankle bone. First, the artery, vein, and nerve are overstretched with every single step taken. Just like any other structure, eventually something has to give. Damage will occur to them, it is just a matter of time. Secondly, there is another structure called the lacinate ligament. This ligament acts as a natural covering of the tarsal tunnel. When overstretching of this ligament occurs it naturally will want to combat this by thickening. So now we have an artery, vein, and nerve that are over-stretched combined with a thickened ligament. The result is an overstretched artery, vein, and nerve being struck with the thickened ligament with every single step taken, a minimum of 10,000 times a day.
Just like the other conditions previously described. The soft tissues can handle this for awhile, but eventually symptoms will occur. The symptoms mainly are felt from damage to the posterior tibial nerve. This is a peripheral nerve, meaning that it is outside of the spine or central nervous system. These peripheral nerves are composed of thousands of bundles of electrical wires that are covered with a special coverings. The outer most "wires" of the posterior tibial neve are responsive for the sensation reception to the bottom of the toes and the deeper we go into the nerve is responsible to the ball of the foot and to the arch, etc. The posterior tibial nerve beside being responsible for the various sensations (light touch, pain, vibration, pressure, etc), it also contains nerve fibers that controls the small blood vessels to the toes, as well as controlling the tens of thousands of sweat and oil glands located on the bottom of the foot.
A very common initial symptom of tarsal tunnel syndrome is numbness in the toes or balls of the feet. This will happen with someone who is trying to exercise. The most common form of exercise is simply walking. It is a cheap and easy exercise to perform. So, the average person sets out to walking off the weight, after about ten to fifteen minutes a strange sensation starts to occur to the foot. It may feel like their sock is wadded up behind the toes, or there is a numbness to the toes, or it may feel like they are walking on a marble. They take their shoe off and don't find a marble or stone, that their sock is not waded up, so they continue to walk. More of the same feeling continues and they quite simply keep walking. Not knowing that they are damaging their nerve to the inner ankle. When they stop walking the trauma to the nerve is stopped and in a matter of time the strange feeling will go away. This is an acute form of tarsal tunnel syndrome.
This vicious cycle will continue and eventually turn from acute to chronic. Chronic tarsal tunnel syndrome is a very serious condition because more damage has occurred to the nerve. Now the symptoms occur on a daily basis, not just during aggressive exercise. Usually, the patient will get out of bed in the morning and there are no symptoms. As the day progresses they start adding up the number of steps taken that day. With every step there is obliteration of the sinus tarsi leading overstretching and compression of the nerve. This causes more and more damage to the nerve until the outer fibers of the nerve no longer transmits the sensations to the brain. Then the patient will loose sensation to that part of the foot which is numbness. The toes and balls of the feet will feel swollen, just like your lip after the dentist has given an injection to fill that cavity in your tooth. Finally, the day has come to an end it is time to go to bed. The patient has stopped walking and no more overstretching or pounding is occurring to the nerve. Since the trauma has stopped the nerve will eventually wake up. It goes from being unconscious to conscious, meanwhile, there are all of these sensations that have been stored up. This is kind of like stepping on a garden hose, the pressure builds up behind the blocked part of the hose and when the blockage is removed there is a surge of water. The same thing happens to the nerve, all of these sensations are waiting to go to the brain but can't. Usually, what happens is that patients with chronic tarsal tunnel syndrome, they go to bed while their feet "wake-up". They will have sharp shooting pains in their feet for while and eventually it will subside and the patient can finally get some sleep.
Again, a vicious cycle continues until finally, there is a continued numb sensation to their feet. That part of the nerve is destroyed and the fibers are completely cut. It can take years and years for this to occur. This commonly happens with patients who are also a diabetic. Diabetes adds a very complicating factor to this condition. When someone looses sensation to their foot they are at risk for puncture wounds, ulcers, etc. An ulceration will usually develop to an area of the foot where a deformity is already present, i.e. a bunion, hammertoe, callus, etc. In a sensate foot, if you rub an area to much it will start to hurt and let you know that something is wrong. You will stop that irritation on your foot. In patient with no sensation they will not feel that pain and continue to walk and wear away the skin to that area and an ulcer is born. The diabetic condition has been known to slow down the healing process (in poorly controlled diabetes). It is possible to further develop bone infection. Once bacteria enters bone, it usually has to be surgically excised.
The conservative treatment of chronic tarsal tunnel syndrome has been directed at masking the symptoms. There are many different medications on the market to help alleviate the nerve pain. Meanwhile, with every step taken continued damage to the nerve will still occur. Other forms of treatment include light-therapy (Anodyne),magnets, etc. which are supposed to help the nerve heal. Meanwhile, nothing has been done to eliminate the obliteration of the sinus tarsi.
The most effective treatment of tarsal tunnel syndrome is first, to place a sinus tarsi stent into the sinus tarsi to prevent it's obliteration. This will also prevent the overstretching of the posterior tibial nerve. The second part of the treatment is to prevent the compression of the artery, vein, and nerve in the tarsal tunnel by performing a tarsal tunnel release and then releasing other bands of tissue that are compressing on the branches of the posterior tibial nerve (calcaneal, medial plantar, and lateral plantar nerves). Peripheral nerves have the ability to regenerate and if given enough time it is possible for the feel to return to their feet.
Here are three very common conditions that are all the result of partial to full obliteration of the sinus tarsi. If ignored these conditions can have a very dramatic effect to the body. If no treatment is initiated more pain and deformity occurs with every step. Eventually, the patient will realize this and decrease the amount of walking they do. This will lead to a decreased metabolism which leads to increased weight. We all know that obesity leads to heart problems and also predisposes someone to becoming a diabetic. The triad of obesity, heart disease, and diabetes known as Syndrome X is the most common medical illness present today.
If these soft tissue deformities of the foot and ankle are ignored and allowed to progress without effective treatment further damage will occur. Instead of being about to cure the obliteration of the sinus tarsi with a sinus tarsi stent, more aggressive rearfoot surgery may be required. Resulting in a longer post-operative recovery with high change of potential complications. As with any disease process the sooner treatment is initiated the faster the recovery. Along with the soft tissue problems, there are usually many other bony deformities present and chronic degenerative arthritic damage is occurring.
If you suffer with any of these soft tissue problems of your foot and ankle and if you have hyperpronation, ask your doctor if a sinus tarsi implant would be the best treatment for you. Let's get rid of what caused the problem in the first place. Don't just put a new tire on your car without balancing that tire first.
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