HIGH ANKLE SPRAIN
(SYNDESMOSIS INJURY)
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related talks: low ankle sprain; achilles tendon tear; broken foot (talus fracture, another type); broken foot (lisfranc fracture); broken heel bone; broken ankle (classic type);
What is a High Ankle Sprain (Syndesmosis Injury)?
A High Ankle Sprain is an uncommon ankle injury that occurs after an severe twisting force that causes one of your ankle ligaments (called the "syndesmosis") to tear.
Lets review some ankle anatomy before we talk specifically about this type of ligament injury. The tibia and fibula are the two bones in the leg. The tibia is the big bone (it bears 90% of our weight) and it forms the inner part of your ankle, while the fibula is a thin bone that holds only 10% of our weight but is important in forming the outer ("lateral") part of our ankle. And then there is a strong ligament that holds the two bones together. This is the Syndesmosis. Without the syndesmosis holding these bones together, the ankle joint is unstable, and cannot support your weight without causing significant pain.
A High Ankle Sprain occurs when the foot rotates outward (external rotation) and it pushes the fibula away from the tibia. This puts too much stress on the Syndesmosis and causes a partial or full tear. A torn syndesmosis makes the ankle unstable because the ankle is a ball and socket joint, where the foot bone (talus) is the ball and the tibia and fibula make up the socket. When the syndesmosis is torn, the fibula and tibia are not held together to form the “socket” and it will split open with placing weight on the ankle.
Its called "High" because the ligament is about 1 inch above the ankle joint (as compared to the common ankle sprain, see talk, which is an injury to other ankle ligaments located just below the joint).
Diagnosing a High Ankle Sprain:
People report a specific incident where they rolled their ankle and then developed pain and swelling. If they remember the injury, they will report that the ankle rolled outward (in contrast to a low ankle sprain when the ankle rolls inward). This occurs in football for example when contact is made to the outside of the leg while the foot is planted.
People report pain and oftentimes inability to stand on the injured leg. When examining the injured leg, a person will report ankle pain when the doctor squeezes the calf muscle (because this squeeze will spread out the tibia and fibula near the ankle).
Not all ankle sprains require an x-ray. However, an ankle fracture is caused by a similar twisting injury (sometimes people will break their ankle and tear their syndesmosis at the same time), and so x-rays are needed to differentiate between the two injuries. Ankle x-rays are also important for high ankle sprains to determine the degree of ligament injury. If the space between the tibia and fibula widens significantly on x-ray, this is an indication of severe syndesmotic injury. But a normal space on x-ray doesn't mean the syndesmosis ok, it can still be sprained.
A ligament is not visible on an x-ray, however, the effect of a torn ligament can sometimes be seen. Our ligaments hold our bones in proper alignment, and therefore, if the ligament is torn, the ankle joint will move out of alignment. If there is too much space between the fibula and tibia, then its likely that the syndesmosis is injured.
Oftentimes an MRI is also ordered because it can show the actual ligament.
Treating a High Ankle Sprain:
Treatment depends on the severity of injury. The severity is graded as 1 (strained but not torn); 2 (torn but widening of ankle seen only with stress); 3 (significant tear, widening even without stress). In a grade 1 injury, the ankle is stable so it just needs to be protected for 6-8 weeks until it heals. The injured leg must return to normal strength and be pain free before returning to sports. Being able to hop up and down 15 times on the injured leg is typically a good indicator that its ok to return.
High ankle injuries are typically more serious than a low ankle sprain (the injury typically takes twice as long to heal), and they often require surgery. If the ankle fails to heal with the above treatment, or if the ankle looks unstable based on the x-rays (the fibula and tibia wide apart) then surgery is indicated.
The procedure is designed to hold the tibia and fibula together while the ligament heal in the correct position. A screw or metal rope ("fiberwire") is used to hold the two bones in place. If screws are used, they are typically removed after 2-3 months (otherwise they may break inside the leg), whereas a tightrope can remain in the leg forever. The surgery is minimally invasive and leaves only a small scar, however, people cannot put weight on that leg for about 3 months after the surgery to give the ligament time to heal.
What is the long term outcome?
The patients are expected to return to their pre-injury activity, although recovery is often slow. Even though a broken bone is more dramatic and sounds worse, ligament injuries can often take much longer than bone to heal, and requires a longer period of immobilization. Some reports suggest that residual symptoms (mild pain and/or weakness) are present at 6 months in up to 40% of people. Its important to take this injury seriously and to get your ankle the necessary time to heal.
Despite the prolonged recovery, when these injuries are given time to heal, there is no increased risk for future arthritis, pain, or disability.
Reference
1) Zalavras C, Thordarson D. Ankle syndesmotic injury. JAAOS 2007; 15: 330-339. full article. review.
2) Wang C et al. Internal fixation of distal tibiofibular syndesmotic injuries: a systematic review with meta-analysis. Int Ortho 2013; 37: 1755-63. full article. review of treatment options.
3) Xenos JS et al. The tibiofibular syndesmosis: Evaluation of the ligamentous structures, methods of fixation, and radiographic assessment. JBJS 1995; 77: 847-856. full article. review.
4) Schepers T. Acute distal tibiofibular syndesmosis injury: a systematic review of suture-button versus syndesmotic screw repair. Int Ortho 2012; 36: 1199-1206. full article. equal goodness.
5) Cottom JM et al. Treatment of syndesmotic disruptions with the Arthrex Tightrope: A report of 25 cases. Foot Ankle Int 2008; 29: 773-80. full article. works well, leave it in.
6) Gerber JP et al. Persistent disability associated with ankle sprains: A prospective examination of an athletic population. Foot Ankle Int 1998; 19: 653-660. full article. syndesmosis injury 40% residual sx at 6 mo.
7) Hopkinson WJ et al. Syndesmosis sprains of the ankle. Foot Ankle 1990; 10: 325-330. full article. take twice as long to heal as common ankle sprain. no longterm risk arthritis.
8) Huber T et al. Motion of the fibula relative to the tibia and its alterations with syndesmosis screws: a cadaver study. Foot Ankle Surg 2012; 18: 203-209. full article. screws change normal ankle motion.
9) Miller AN et al. Functional outcomes after syndesmotic screw fixation and removal. JOT 2010; 24: 12-16. full article. removing screws improves fxn, no loss reduction.
10) Williams BT et al. Ankle syndesmosis: a qualitative and quantitative anatomic analysis. Am J Sports Med 2014. full article. anatomic measurements.