Posterior Ankle Impingement
What are the important structures on the backside of the ankle?
The ankle joint is the joint between the leg bones (tibia and fibula) and the ankle bone (talus). Below the talus is the heel bone. The joint between the talus and heel bone is called the subtalar joint; it lies below the ankle joint. The talus has a bony prominence in the back next to the flexor hallucis longus (FHL) tendon. This is the tendon that moves the big toe downward toward the floor.
The bony posterior prominence might be the cause of ankle pain in some people if it is large (called steida process) or it is not completely fused with the talus bone (called an os trigonum).
Pain might also occur if the FHL tendon gets irritated. This can happen if the tendon doesn't fit well because the tunnel is too tight or the tendon is too big, or if the tendon is inflamed and swollen (called tenosynovitis).
An ankle sprain may cause a tear of the posterior ankle ligaments. The torn pieces can flip inside the joint. They can get pinched between the joint surfaces and cause pain. This problem is called posterior soft tissue impingement.
The Achilles tendon attaches to the back of the heel bone. It can get pinched by a prominent piece of bone at the top of the heel (called a Haglund's deformity). This can lead to wear of the Achilles tendon and calcium deposits in the tendon (called insertional Achilles tendonitis).
When surgery may be needed?
Surgery is indicated when non operative treatment fails. The pain from a large os trigonum, an FHL problem or posterior soft tissue impingement tends to be deep. It typically increases with downward motion of the ankle. Football players and ballet dancers are at higher risk for these problems.
The pain from Achilles tendonitis is typically at the surface in back of the heel. This pain often increases when wearing closed shoes and improves with shoes that have open heels.
What is posterior ankle arthroscopy?
Posterior ankle arthroscopy is a key-hole procedure used to look at and treat problems at the backside of the ankle joint.
What are the details of the procedure?
With the patient lying face-down or on the side, the orthopaedic foot and ankle surgeon makes two incisions on either side of the Achilles tendon. The arthroscope is inserted and part of the fatty tissue at the back of the ankle is removed to create a workspace.
The problem causing the pain is identified and treated accordingly using various small instruments:
- The os trigonum is freed from the surrounding soft tissues then removed.
- The FHL tenosynovitis is cleaned up using a shaver and the tunnel is released if necessary.
- The torn ligaments causing posterior soft tissue impingement are cleaned up with the shaver.
- The Haglund's deformity is removed using a special burr.
What happens after surgery?
The post-operative dressing is usually a splint or bulky soft dressing. A post-op shoe or boot may be added for protection. Weight bearing may be restricted depending on the surgery that is done.
Elevation is advised in the first 48 hours after the procedure. The stitches are removed in 12 to 14 days and exercises can be started. Early motion of the ankle and foot joints is typically recommended. Formal physical therapy may be required.
What are the potential complications
There is a small risk of infection or clots in the veins. Injury to blood vessels and nerves is rare but remains a complication. Other complications include numbness on the sole of the foot, sensitive skin on the outside part of the foot and Achilles tendon tightness.