Anterior talofibular ligament (ATFL) injury is the most common of the ligament injuries that can occur as part of the lateral ligament complex injuries 2. The injuries can comprise either soft tissue tears, avulsion fractures or both.
ATFL injuries typically occur with an inversion injury to the ankle, either with or without plantar flexion. Approximately two-thirds of ankle sprains tend to be isolated injuries to the ATFL (the ATFL is the weakest ligament in the lateral collateral complex of the ankle). There is general agreement that avulsion is more common at the fibular than the talar end of the ligament 2.
AMA classification 8,9:
- grade I: ligament stretch
- partial tear
- partial loss of movement
- mild to moderate joint instability
- complete tear
- inability to bear weight
- significant joint instability
Many orthopedists favor a functional approach based on clinical examination:
grade I: stable injury
- provocative maneuvers do not elicit increased upper ankle joint laxity
- no ligament in the lateral complex is completely ruptured
grade II: unstable
- ruptured ATFL
- increased upper ankle joint laxity
grade III: unstable
- ruptured calcaneofibular ligament (CFL)
- increased upper ankle joint laxity
There are other grading systems, of course, such as the anatomic classification or grading by clinical presentation symptoms 9.
Many show an associated avulsion fracture at either the fibular end or, less commonly, the talar end.
May show ancillary features such as an ankle joint effusion and/or overlying lateral malleolar soft tissue swelling.
Has been shown to have high sensitivity and specificity rates for chronic ATFL tears 6.
Both the anterior and posterior talofibular ligaments are usually seen on a single axial image obtained slightly distal to the tibiofibular ligaments 4.
MRI may show discontinuity, detachment, thickening, thinning, irregularity of the ligament, a bright rim sign 5 or an associated bony avulsion. Heterogeneity with increased intraligamentous signal intensity on fat-suppressed or T2-weighted images is indicative of intrasubstance edema or hemorrhage.
- fluid within the joint serves to highlight the anterior talofibular ligament on T2-weighted images
- the ligament appears as a thin, straight, low signal intensity band extending from the talus to the fibular malleolus
- a bright rim sign (cortical defect with a bright dot-like or curvilinear high signal intensity lesion) may be seen on T2 weighted imaging
On MRI consider:
anterolateral impingement syndrome of ankle 4
- repetitive synovial inflammation secondary to chronic lateral ankle instability produces a soft-tissue “mass” consisting of hypertrophic synovial tissue and fibrosis within the lateral gutter
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- 5. Lee MH, Cha JG, Lee YK et-al. The bright rim sign on MRI for anterior talofibular ligament injury with arthroscopic correlation. AJR Am J Roentgenol. 2012;198 (4): 885-90. doi:10.2214/AJR.11.6868 - Pubmed citation
- 6. Hua Y, Yang Y, Chen S et-al. Ultrasound examination for the diagnosis of chronic anterior talofibular ligament injury. Acta Radiol. 2013;53 (10): 1142-5. doi:10.1258/ar.2012.120171 - Pubmed citation
- 7. Oae K, Takao M, Uchio Y et-al. Evaluation of anterior talofibular ligament injury with stress radiography, ultrasonography and MR imaging. Skeletal Radiol. 2010;39 (1): 41-7. doi:10.1007/s00256-009-0767-x - Pubmed citation
- 8. Balduini FC, Vegso JJ, Torg JS, Torg E. Management and rehabilitation of ligamentous injuries to the ankle. Sports medicine (Auckland, N.Z.). 4 (5): 364-80. Pubmed
- 9. Mark E. Easley, Sam W. Wiesel. Operative Techniques in Foot and Ankle Surgery. ISBN: 9781608319046