E4618. Oops I Sprained It Again! Or Maybe Not! Common MR Features and Pitfalls of Ankle Ligamentous Injuries
  1. Nga Nguyen; University of Texas Medical Branch
  2. Nahyun Jo; University of Texas Medical Branch
  3. Xuan Tran; University of Texas Medical Branch
  4. Azin Aein; University of Texas Medical Branch
  5. James Roberts; University of Texas Medical Branch
  6. Deborah Stedman; University of Texas Medical Branch
Ankle ligamentous injury or sprain is the most common type of ankle injury in the United States. Despite the prevalence, trainees often find imaging of the ankle ligaments a difficult learning issue, especially with a more advanced modality like MRI. Understanding the normal ankle anatomy, including osseous structures, ligaments and tendons is half the battle. Once anatomical landmarks become familiar, a mental checklist of differential diagnosis, common anatomic variants, and frequently encountered pitfalls is needed to solidify the imaging interpretations.

Educational Goals / Teaching Points
After reading this educational poster, the reader will be able to identify the ankle ligamentous complexes and major anatomic landmarks, recognize MRI features of major ligament complex injuries and mimics and incorporate common “blind spots” to ankle imaging search patterns.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
This educational exhibit presents the normal anatomy of hindfoot ligaments, including lateral collateral ligaments, medial collateral (deltoid) ligaments, tibiofibular syndesmosis, spring ligament complex and sinus tarsi. Common MRI features of ligamentous injuries and secondary signs of trauma, such as join effusion, soft tissue edema, and surrounding tendon or bony injuries are also demonstrated. Frequently encountered pitfalls in evaluating this complex territory will be emphasized. For example, a physiologic gap between the anterior talofibular fascicles may be mistaken for a tear. In a similar manner, the fibrofatty tissue separating the posterior talofibular fascicles may be misdiagnosed as a low-grade sprain. A commonly encountered ganglion cyst with high T2 signals embedded in a ligament should not be confused with effusion from a ligamentous injury. Small vessels adjacent to a ligament may also be misinterpreted as a tear. Furthermore, depending on the timing of MRI, a ligamentous injury may have completely healed and appear normal at that point. However, a search for possible source of ankle pain should be further pursued, as fibrous scar tissue may serve as a source of impingement. Evaluation of the sinus tarsi, a common “blind spot,” will also be discussed.

MRI of ankle ligamentous injuries may potentially be a challenge for young trainees due to the inherent anatomic complexity. Recognizing the normal findings, adjacent structures, and various pathology of the ligaments other than traumatic causes plays a significant role in achieving the accurate diagnosis.