Research Review by Dr. Shawn Thistle©

Date:

Sept. 2006

Study Title:

Ankle syndesmosis injuries: Anatomy, biomechanics, mechanism of injury, and clinical guidelines for diagnosis and intervention

Authors:

Lin C, Gross MT & Weinhold P

Publication Information:

Journal of Orthopaedic & Sports Physical Therapy 2006; 36(6): 372-384.

Summary:

The ankle is one of the most commonly injured joints in competitive and recreational athletes. The syndesmotic sprain, commonly referred to as a "high ankle sprain" occurs less frequently than a lateral ankle sprain, but can be just as, if not more, debilitating.

For this reason it is crucial that therapists interacting with active clients be aware of this condition, and the unique assessment and treatment requirements it demands. It is more difficult to diagnose than lateral sprains, and can become a very protracted and frustrating rehabilitation for the patient if not managed properly.

Syndesmotic sprain involve disruption of the ligamentous structures that join the distal tibia and fibula, proximal to the ankle joint. Existing data indicate that the syndesmosis is involved in1-18% of all ankle sprains, and there is general consensus that they cause more time lost from athletic participation than other ankle sprains (almost double!).

ANATOMICAL CONSIDERATIONS
  • the distal tib-fib articulation is comprised of three main ligaments:
    1. the anterior inferior tibiofibular ligament (AITFL)
    2. the posterior inferior tibiofibular ligament (PITFL)
    3. the interosseous ligament
  • a fourth ligament - the inferior transverse tibiofibular ligament - is located posterior to the talus and covers its superior aspect, and is often considered a separate component of the PITFL
  • of the 4 ligaments, the AITFL and PITFL are considered the primary stabilizers
  • the AITFL is normally weaker than the PITFL, and injury to the AITFL is normally accompanied by damage to the interosseous ligament
  • the interosseous ligament acts as a buffer to axial loading in the leg, assisting in force transfer from tibia to fibula
  • as an intact ankle joint moves from plantar flexion to full dorsiflexion, the mortise joint widens only ~ 1mm, and the fibula only rotates ~ 2° relative to the tibia - indicating that the three ligaments provide a tremendous amount of stability
  • when considering the syndesmosis, it is important to remember that the anterior talar dome is wider than the posterior aspectv
MECHANISIM OF INJURY
  • there are three primary MOIs proposed for syndesmotic injuries:
    1. external rotation of the foot
    2. eversion of the talus within the ankle mortise
    3. excessive dorsiflexion
  • combinations of the above MOIs are possible
  • all three MOIs produce wedging of the talus into the syndesmosis, pushing the fibula laterally away from the tibia
  • chronic instability of the syndesmosis may result, which can alter the contact pattern or shear stress about the ankle - potentially predisposing the patient to early degenerative joint disease
  • common sports for syndesmotic injuries include skiing, football, soccer, and any other turf sports requiring planting and cuttingv
CLINICAL HISTORY / ASSESSMENT
  • external rotation of the foot is the most common reported mechanism - its presence should alert the clinician to check for syndesmotic sprain
  • pain is localized to the AITFL, and may extend proximally
  • pain is increased by passive or forced dorsiflexion, or external rotation of the foot
  • normal heel-toe walking may be replaced by toe walking to prevent dorsiflexion
  • severe swelling is not normally present
  • isolated syndesmotic sprain is thought to be rare - more often accompanied by injury to the deltoid ligament complex
  • clinical tests for syndesmotic sprain can include:
    1. external rotation (Kleiger) test - patient sits on the edge of the table - examiner stabilizes the proximal leg with one hand and externally rotates the foot with the other - a positive test is pain at the anterolateral aspect of the distal tib-fib joint (note: pain on the medial side of the ankle may indicate deltoid ligament injury)
    2. point test - progressively harder palpation of the AITFL - a positive test is local pain
    3. heel thump test - examiner holds the proximal leg and directs firm impact force through the bottom of the heel - a positive test is pain in the tib-fib articulation
    4. squeeze test - attempts to promote separation of the distal tib-fib by gently squeezing the tib-fib progressively from distal to proximal (more separation distally as you move proximally) - a positive test is pain at the distal tib-fib articulation
    5. forced dorsiflexion - attempts to force the wider anterior talar dome into the syndesmosis - a positive test is pain at the tib-fib articulation
    6. one-legged hop test - it has been reported that patients with syndesmosis injuries cannot complete ten one-legged hops on the involved side due to pain (only use this test if the previous tests are negative - further separation of the syndesmosis could occur with this test)
  • sensitivity and specificity values for the above tests have not been sufficiently attained
  • normally, imaging studies are not required to diagnose this injury, but can be confirmatory (and may also be useful to rule out fracture)
  • radiographically - the tibiofibular clear space should be < 6 mm if the syndesmosis is intact, and the tibiofibular overlap in the mortise view should be > 1 mm (each measurement made 1cm above the tibial plafond)
TREATMENT
  • conservative treatment is recommended in the absence of fracture
  • initially - rest, ice, compression, elevation (RICE), non-weight-bearing with or without a posterior splint (or other orthotic device)
  • use external braces with caution, as external compressive forces (with straps etc.) could separate the syndesmosis
  • electrotherapy/ice can be used for pain and inflammation
  • ROM exercises (ankle pumps etc.) can be used in the early phase
  • once weight-bearing is initiated (after pain subsides), a heel lift to prevent excessive dorsiflexion can be employed and more advanced ROM, stretching and strengthening exercises can begin (including low level balance training)
  • progression to walking, walk-to-jog, and jog-to-run, then cutting and sport-specific rehab
  • timelines for treatment and rehabilitation vary depending on severity of initial injury

Conclusions & Practical Application:

Syndesmosis injuries are relatively rare, but are frequently misdiagnosed and consequently mismanaged. A thorough history and physical examination are keys in recognizing this condition. Imaging studies may be required to rule out fracture, or confirm the diagnosis.

Recovery is generally slower for this injury than lateral ankle sprains, and early management often requires rigid immobilization. Surgical intervention is only required for severe tears, or those that are not responsive to conservative care and rehabilitation.