Distal tibiofibular syndesmosis injuries are a relatively frequent ankle injury, although less common than a fracture or lateral ankle sprain. They are estimated to comprise ~10% (range 1-20%) of ankle injuries.
On this page:
Epidemiology
Associations
fracture / bone contusion
talar dome osteochondral injury 2
Pathology
The mechanism of injury is uncertain but thought to be the combination of forceful foot external rotation with concomitant leg internal rotation 2. Injuries can occur to one or more of the structures that make up the distal syndesmosis 1:
Radiographic features
Plain radiograph
Distal syndesmotic injury can easily be inapparent and therefore missed on plain x-ray, especially if it is not accompanied by a nearby fracture or widening of the tibiofibular clear space 2,3. Numerous measurements have been proposed for indirectly demonstrating syndesmotic injury but these vary across studies with no formed consensus. Some studies have shown 3:
tibiofibular clear space >5.3 mm (AP view) has a sensitivity of 82% and specificity of 75% for syndesmotic injuries 8
-
<6 mm (AP view)
<2.8 mm (mortise view) has a sensitivity of 36% and specificity of 87% for syndesmotic injuries
medial clear space >4-5 mm (mortise view) is considered indicative of deltoid ligament rupture and an indirect sign of a syndesmotic injury
Ultrasound
Aside from being readily available, ultrasonography has the added benefit of being a real-time dynamic modality, allowing the operator to perform maneuvers on the ankle during imaging. The contralateral, uninjured, ankle can be imaged for comparison.
It can demonstrate:
anterior inferior tibiofibular ligament injury 3,5, associated clear tibiofibular space diastasis 7, and bulging joint capsule 5
interosseous membrane injury 6
MRI
MRI has been shown to accurately detect injuries to the ligamentous structures of the distal tibiofibular syndesmosis 1-3. The anterior inferior tibiofibular ligament is the one most often involved in such injuries and the most convenient to identify 2. Direct signs of a ligamentous tear include 2,4:
abnormal course of the ligament
irregular contour of the ligament
inability to visualize the ligament
Indirect signs 4:
tibiofibular joint space fluid
prolapsed interspace fat
Signal characteristics
-
T2
acute ligamentous injury: hyperintense signal in the ligament with surrounding edema
chronic injury: thickened or disrupted ligament without edema
-
T1 C+
acute injury: injured ligaments enhance intensely
Practical points
-
injuries to the high ankle tend to occur in the following order:
in intermediate injuries without syndesmotic widening on non-weight bearing x-rays and MRI, stress weight-bearing imaging may be of benefit and if instability (dynamic widening) is demonstrated then surgery is typically indicated
Treatment and prognosis
Surgical management options include an ORIF with syndesmotic screw(s) or a cord device, e.g. TightRope.
Unable to process the form. Check for errors and try again.