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New Way to Treat Posterior Ankle Impingement in Dancers and Other Athletes

Posted on: 12/22/2008
The senior author of this article developed a minimally invasive way to treat posterior ankle impingement. Impingement is the pinching of soft tissue, bone fragments, or scar tissue causing painful and limited ankle motion. Plantar flexion (pointing the toe) is affected most often.

Posterior ankle impingement is caused by traumatic injury or overuse in dancers, soccer players, runners, and other athletes. Sometimes dancing or running on a hard surface contributes to the problem.

In other cases, there is a slight difference in the normal foot and ankle anatomy that eventually leads to posterior ankle impingement. The joint capsule may be thickened causing pain when it gets pinched between two bones in the ankle.

There may be bone fragments inside the joint that have broken off the bone and become free-floating pieces that get stuck between two bones. Whatever the cause, the end result is the same: chronic ankle pain along the back of the ankle (at rest and with palpation), pain with movement, and loss of ankle plantar flexion.

The new procedure is called a two portal posterior endoscopic approach. A special tool called an endoscope was used to access the ankle joint through points called portals. A small incision was made and the scope was slid into the joint from the back of the ankle. A tiny TV camera on the end of the scope gave the surgeon a view inside the joint. A detailed description of the surgical procedure was provided in the article.

In this study, the endoscopic approach was used to treat 55 patients with posterior ankle impingement. All had posterior impingement syndrome from overuse (35 per cent) or trauma (65 per cent). Conservative (nonoperative) care was the first line of treatment. When that was unsuccessful, surgery was done to remove the offending tissue (e.g., bone fragments, scar tissue, thickened joint capsule).

One common cause of posterior impingement syndrome is called the os trigonum. There is an extra piece of bone present (usually at birth) in affected individuals. It is located behind the talus bone (part of the ankle complex). It is connected to the talus by a band of fibrous tissue. When this bony bump gets separated from the main body of the talus, it is referred to as an os trigonum.

For the person who has an os trigonum, pointing the toes downward catches the os trigonum between the ankle and heel. The repetitive force downward on the os trigonum every time the foot is pointed causes the bone fragment to pull loose. As the os trigonum pulls away, the tissue connecting it to the talus is stretched or torn. The area becomes inflamed causing pain and loss of ankle motion.

Results were compared with outcomes reported in other studies when the same surgery was done with an open technique. Measures used to compare the results included score on the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score (measures of pain, function, and alignment) and the Tegner score (measure of activity level). Time to return to work and to sports activities were also recorded and compared between the endoscopic and the open procedure.

The posttraumatic group was able to return to work in about one week. The overuse group needed more time with an average return-to-work return rate as two and a half weeks. However, it took longer for the posttraumatic group to get back on the field or involved in sports once again (11 weeks) compared with the overuse group (eight weeks).

These figures also corresponded with function (better function in the overuse group that returned to sports faster). And the overuse group was much happier with their results compared with the posttraumatic group.

There were two main differences between patients who had minimally invasive endoscopic surgery and those who had open surgery for posterior ankle impingement. These were reported as far fewer complications and faster recovery in the endoscopic group.

Patients whose impingement was caused by overuse had better results in both the endoscopic and open surgery procedures. The authors speculated that this may be related to more pathology (damage) in the ankles of patients with posttraumatic impingement. Not only is there an os trigonum after trauma, but also tendinitis of the flexor hallucis longus develops in the majority of patients. The tendon of this muscle in the foot lies in a groove that goes behind the talus, under the calcaneus (heel bone), and inserts into the base of the big toe. The tendinitis occurs as a result of displacement of the os trigonum.

The authors conclude that a skilled surgeon can operate endoscopically to treat posterior ankle impingement. The two-portal method from the back of the leg gives easy access to the ankle joint, flexor hallucis longus tendon, and os trigonum. Important nerves and blood vessels are avoided with this method. Fewer complications means a faster recovery, which is important in the typical patient population (ballet dancers, athletes).

P. E. Scholten, MD, et al. Hindfoot Endoscopy for Posterior Ankle Impingement. In The Journal of Bone & Joint Surgery. December 2008. Vol. 90-A. No. 12. Pp. 2665-2672.

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