Distal tibiofibular syndesmosis injury
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.
Pathology
The mechanism of injury is uncertain but thought to be the combination of forceful foot external rotation with concomitant leg internal rotation . Injuries can occur to one or more of the structures that make up the distal syndesmosis:
- anterior inferior tibiofibular ligament (AITFL)
- posterior inferior tibiofibular ligament (PITFL)
- transverse tibiofibular ligament
- interosseous membrane
Associations
- anterior talofibular ligament injury
- fracture / bone contusion
- talar dome osteochondral injury
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. . Numerous measurements have been proposed for indirectly demonstrating syndesmotic injury but these vary across studies with no formed consensus. Some studies have shown :
- tibiofibular clear space >5.3 mm (AP view) has a sensitivity of 82% and specificity of 75% for syndesmotic injuries
- tibiofibular overlap
- <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 , associated clear tibiofibular space diastasis , and bulging joint capsule
- interosseous membrane injury
MRI
MRI has been shown to accurately detect injuries to the ligamentous structures of the distal tibiofibular syndesmosis . The anterior inferior tibiofibular ligament is the one most often involved in such injuries and the most convenient to identify. Direct signs of a ligamentous tear include:
- ligament takes an abnormal course
- ligament assumes an irregular contour
- AITFL cannot be visualized
Indirect signs :
- 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 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
Surgical management options include an ORIF with syndesmotic screw(s) or and cord device e.g. TightRope.
Siehe auch:
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Assoziationen und Differentialdiagnosen zu Ruptur distale tibiofibulare Syndesmose:
