Dispelling The Misconceptions About Subtalar Arthroereisis

Michael E. Graham, DPM, FACFAS

   For argument’s sake, even if these structures were damaged, this artery is not the main source of blood to the talus. There is a complex network of blood vessels supplying blood to the talus. The upper surface of the sinus tarsi is not perfectly round and it has an apex to it. The good news is that the artery and nerve are located at the highest level of the peak. There is a space between that peak and where the talus would come into contact with the sinus tarsi device. These devices do not traumatize the artery and nerve to the sinus tarsi.

How Arthroereisis Affects The Achilles Tendon

Myth: Any time one inserts a sinus tarsi stent, the Achilles tendon needs to undergo a lengthening procedure. Many foot physicians believe it is the tight Achilles tendon that forces the displacement of the talus, leading to the obliteration of the sinus tarsi. I have found this not to be true. Furthermore, it is only on a rare occasion that I find it necessary to perform a lengthening procedure. Usually, it is only in an extreme case of flatfoot when the condition is so severe that one needs to perform other osseous procedures.

   If the Achilles tendon is the primary etiology, then the talus should stabilize itself after a lengthening procedure of the tendon. This does not occur. One can make a reverse argument that instability of the talus could cause the Achilles to contract and tighten.

   The gastroc-soleal complex serves as a powerhouse to aid in the propulsion of the foot. It is a strong supinator of the foot. In patients with hyperpronation, these muscles have to work extra hard to overcome the excessive pronation and perform their regular duty. During the gait cycle, the Achilles immediately senses this excessive strain via mechanoreceptors within the tendon and muscle belly, and action occurs to counteract this pathologic strain on the tissues.

   Once one has restored the subtalar joint complex to a better alignment, this eliminates the excessive pronatory forces to the tendon, therefore eliminating the excessive strain on the Achilles. Due to the decreased strain, the mechanoreceptors are able to relax, leading to an “internal” lengthening of the gastroc-soleal complex.

   I have had many patients with chronic Achilles tendinitis in whom I have performed a subtalar arthroereisis procedure without an Achilles tendon lengthening. Within a short period of time, there was resolution of Achilles tendinitis. If a subtalar arthroereisis procedure would place an additional strain on the Achilles tendon, it would make the tendinitis get worse, not better.

   Furthermore, in regard to patients in whom I have performed the subtalar arthroereisis without an Achilles tendon lengthening, I have not had one patient ever complain of Achilles tendon pain or the development of Achilles tendinitis.

Subtalar Arthroereisis And Flatfoot: What You Should Know

Myth: Subtalar arthroereisis is for flat feet only. This is where some surgeons get into trouble with subtalar stabilization with a sinus tarsi stent. There are many definitions for flatfoot. Some think it implies only a foot that is rigid and completely flat with no arch while others define flatfoot as any foot with a lower than normal arch.

   The true indication of a subtalar arthroereisis procedure is instability of the talus on the calcaneus leading to partial or full obliteration of the sinus tarsi. This pathologic condition can occur in patients from ages 3 to 93. Many patients have a very high calcaneal inclination angle, which indicates a high arched foot, yet they exhibit the instability of the subtalar joint complex and suffer from the symptoms of this very common condition.

   The ideal patient for subtalar arthroereisis exhibits the deformity but cannot achieve stabilization with custom-molded orthoses. This patient also does not have a deformity that is severe enough for more aggressive surgery. In some situations, the surgeon pushes the envelope and tries an arthroereisis in semi-flexible or rigid flatfoot conditions. Most likely, the procedure will fail in these patients. Arthroereisis as a standalone procedure works the best in mild to moderate cases. Severe cases of flexible flatfoot are better served with a combination of arthroereisis and rearfoot reconstructive procedures.

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