A high ankle sprain differs from a regular ankle sprain in the ligament which is injured and the recovery period that can be expected. A high ankle sprain, or a “syndesmosis injury” is a more serious ankle injury involving the ligaments above the ankle that join the tibia and fibula together (the two shin bones). It needs to be correctly identified and treated differently to a regular ankle injury. Failure to recognize a syndesmosis sprain may lead to inappropriate treatment and prolonged disability.

Injuries to the ankle syndesmosis are most likely to result from excessive rotation of the ankle (adduction or abduction of the foot), extremes of dorsiflexion, or combinations of dorsiflexion with adduction or abduction. The type of injury that produces syndesmosis sprains commonly occurs in sports played on turf with cleated shoes.

Anatomy

The tibia and fibula are held together around the ankle joint by strong ligaments. The ligaments that stabilize this joint are the anterior inferior tibiofibular ligament, the posterior inferior tibiofibular ligament, and the interosseous ligament. The most distal and inferior aspect of the interosseous membrane also helps to stabilize this joint.
The interosseous ligament is a thickening of the distal aspect of the interosseous membrane and is thought to act as a “spring,” allowing for slight separation between the medial and lateral malleolus during dorsiflexion at the talocrural joint.

What is the best treatment?

Depending on the grade of injury, conservative treatment can be very effective. Conservative therapy involving rehabilitation and tissue injury care and is appropriate for Grade I and II injuries, while Grade III injuries require surgical intervention. It is important to first grade the level of injury and then it can be determined whether a period of rest and graduated return to activity is appropriate or whether a period of time in a cam walker boot is needed to allow healing the occur. These treatments will be effective if the joint is stable and the tibia and fibula are not separating (this can be assessed by a weight bearing x-ray film). If the injury is unstable, referral to an orthopaedic surgeon is necessary where surgery may be the required treatment. If surgery is indicated then a "syndesmotic screw" can be placed between the tibia and fibula to hold the bones in proper position while the syndesmotic ligament heals. There are several methods of fixation of syndesmotic injuries, all with potential risks and benefits. It is a relatively safe and well-tolerated surgical procedure with approximately six months recovery period.

Links

For more information regarding high ankle sprains see:

http://www.eorthopod.com/content/ankle-syndesmosis-injuries
http://orthopedics.about.com/od/sprainsstrains/a/syndesmosis.htm

References:

Susan A. Norkus and R. T. Floyd. The Anatomy and Mechanisms of Syndesmotic Ankle Sprains. J Athl Train. 2001 Jan–Mar; 36(1): 68–73.

Brosky T, Nyland J, Nitz A, Caborn DN. The ankle ligaments: consideration of syndesmotic injury and implications for rehabilitation. J Orthop Sports Phys Ther. 1995 Apr;21(4):197-205.