MRI Web Clinic — August 2003

Ankle Ligamentous Injury
Mark H. Awh, M.D.

Clinical History: 32 year-old male s/p twisting injury while playing basketball. Fat-suppressed T2-weighted axial (1a) and proton density weighted coronal (1b) images are provided. What are the findings? What is your diagnosis?

1a
1b
Figure 1:

Fat-suppressed T2-weighted axial (1a) and proton density weighted coronal (1b) images

Findings

2a
2b
Figure 2:

(2a) The T2-weighted axial image reveals edema and laxity along the course of the anterior talofibular ligament (arrow) and a bone bruise of the talus deep to the ligament attachment (arrowhead). (2b) Proton-density weighted coronal images reveal edema and soft tissue thickening throughout the expected location of the calcaneofibular ligament (arrow).

Diagnosis

Grade III ankle sprain with disruption of the anterior talofibular ligament and the calcaneofibular ligament.

Discussion

Ligamentous injuries of the ankle, particularly those at the lateral side, are one of the most common traumatic lesions seen in adults. Lateral ligamentous injuries may be classified based on the severity of injury. In Grade I injuries, partial disruption of the anterior talofibular ligament is present. Grade II injuries have at least partial disruption of the anterior talofibular ligament and the calcaneofibular ligament. Grade III injuries result in complete ligamentous disruption of the anterior talofibular and/or calcaneofibular ligaments, often with ankle instability. The third component of the lateral ligamentous complex, the posterior talofibular ligament, is quite strong and is rarely injured except in cases of ankle dislocation.

The anterior talofibular ligament is consistently visible on axial MR images (C), and is the most frequently torn ligament of the lateral complex. The calcaneofibular ligament and the posterior talofibular ligament are usually well seen on coronal MR images (D), and the calcaneofibular ligament can also be visualized on axial images (E), coursing deep to the peroneal tendons. The calcaneofibular ligament, when torn, is typically injured in conjunction with anterior talofibular ligament tears.

3a
Figure 3:

(3a) A T2-weighted axial image reveals the normal anterior talofibular ligament (arrow) as it courses from the lateral malleolus to a small tubercle at the lateral talar body.

4a
Figure 4:

(4a) The normal calcaneofibular (arrow) and posterior talofibular (arrowhead) ligaments are well seen on this T2 weighted coronal image.

5a
Figure 5:

(5a) The calcaneofibular ligament (arrow) is also apparent as it courses deep to the peroneal tendons on this T2-weighted axial view.

 

 

Ligamentous injuries at the ankle are reliably seen with MR, manifesting as abnormal laxity or discontinuity within the affected ligament or as soft tissue thickening and edema about the ligament in cases of partial tearing.1,2 Chronically sprained ligaments are seen as abnormally thickened structures without associated edema (6a).

 

6a
Figure 6:

(6a) A T2-weighted axial image reveals a thickened anterior talofibular ligament (arrow) in a professional basketball picture with a chronic ligamentous injury.

Soft tissue impingement may occur after a lateral ligamentous injury of the ankle and results in chronic pain with mechanical symptoms.3 Sites of soft tissue impingement include anterolateral, posterior, and syndesmotic, with anterolateral impingement being the most common. On MR, abnormal soft tissue thickening may be seen at the lateral gutter (7a), generally demonstrating relatively low signal intensity on both T1 and T2 weighted images. At arthroscopy, a hyalinized mass is seen in this region. Surgical resection of this abnormality is generally curative.

 

7a
Figure 7:

(7a) A T2-weighted axial image reveals the characteristic low signal intensity soft-tissue thickening (arrow) within the lateral gutter in a patient with anterolateral impingement following a remote ankle sprain.

Conclusion

MRI reliable visualizes ligamentous anatomy and pathology at the ankle, and is being used with increasing frequency in patients following lateral ankle sprains. As surgical indications and techniques for lateral ligamentous reconstruction continue to evolve, the value of MRI in the preoperative assessment of these patients should only increase.

References

1 Mesgarzadeh M, Schneck CD, Tehranzadeh J, et al. Magnetic resonance imaging of the ankle ligaments: emphasis on anatomy and injuries to lateral collateral ligaments. Magn Reson Imaging Clin N Am 1994; 2:39-58.

2 Bencardino J, Rosenberg ZS, Delfaut E. MR imaging of sports injuries of the foot and ankle. Magn Reson Imaging Clin N Am 1999; 7:131-149.

3 Martin D, Curl W, Baker C. Arthroscopic treatment of chronic synovitis of the ankle. Arthroscopy 1989; 5:110.


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