MRI Web Clinic — July 2010

High Ankle Sprains
Leland Y. Tsao

Clinical History: A 17 year-old female injured her right ankle 4 days ago during a soccer game. MRI of the ankle was obtained with axial fast spin-echo T2-weighted (1a), coronal STIR (1b), and oblique coronal proton density-weighted (1c) images. What are the findings? What is your diagnosis?

1a
1b
1c
Figure 1:

Axial fast spin-echo T2-weighted (1a), coronal STIR (1b), and oblique coronal proton density-weighted (1c) images.

 

 

 

Findings

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Figure 2:

The axial fast spin-echo T2-weighted image through the distal tibiofibular syndesmosis demonstrates buckling and anterior protrusion of the anterior inferior tibiofibular ligament (arrow). Part of the posterior inferior tibiofibular ligament (arrowhead) is also visualized and appears intact.

 

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Figure 3:

The coronal STIR image through the anterior inferior tibiofibular ligament shows irregular wavy morphology and increased signal in the ligament (arrow), with adjacent soft tissue edema.

 

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Figure 4:

An oblique coronal proton density-weighted image through the anterior inferior tibiofibular ligament confirms discontinuity of the ligament at the fibular insertion (arrow).

 

Diagnosis

Complete tear of the anterior inferior tibiofibular ligament at its fibular insertion, consistent with an anterior ankle syndesmotic injury (high ankle sprain).

Introduction

Ankle sprains are the most common injury sustained by athletes1, and account for up to 10% of emergency room visits.2,3 The majority of ankle sprains involve the lateral ligament complex.2,3 A significant minority of patients with ankle trauma are diagnosed with injuries of the distal tibiofibular syndesmosis, ranging from 1% to 18% in the literature.4,5 Ankle injuries involving the syndesmotic ligaments are commonly called “high ankle sprains”, and are associated with a greater risk of residual ankle dysfunction and persistent pain.5 Athletes who sustain high ankle sprains generally require twice as long to return to their previous level of competition, compared to ankle sprains of similar severity which do not involve the syndesmosis.6

Anatomy

The distal tibiofibular syndesmosis is stabilized by the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and transverse tibiofibular ligament (TrTFL) (also called the transverse interosseous ligament or inferior transverse tibiofibular ligament) (Figure 5a).7,8 The most inferior portion of the interosseous membrane (frequently called the interosseous ligament)8 and deep deltoid ligaments1 also contribute to syndesmotic stabilization.

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Figure 5:

Anterior (left) and posterior (right) 3D renderings of the syndesmotic ligaments at the ankle demonstrate the anterior inferior tiobiofibular ligament (AITFL), the posterior inferior tibiofibular ligament (PITFL), transverse tibiofibular ligament (TrTFL) and the interosseous membrane (IM).

 

On MRI, the normal ligaments are visualized as hypointense bandlike structures on all pulse sequences, consistent with their predominant collagen fiber content.9 The AITFL courses from the anterolateral tibia (Chaput’s tubercle) laterally and inferiorly to the anterior lateral malleolus (Wagstaffe’s tubercle). The PITFL courses from the posterior lateral tibial tubercle (also known as Volkmann’s tubercle or the posterior malleolus) to the posterior aspect of the lateral malleolus. The TrTFL is located just inferior and deep to the PITFL, extending from the posterior lateral malleolus to the posterior tibia and posterior surface of the medial malleolus.5,7,8 The interosseous membrane is located between the distal diaphysis of the fibula and tibia, usually terminating about 1 to 2 cm above the tibial plafond. A normal synovial recess extends superiorly from the tibiotalar joint into the interosseous region; the interosseous ligament forms the roof of this recess, and represents the lower margin of the interosseous membrane.10

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6b
Figure 6:

Contiguous axial fast spin-echo T2-weighted images from the same patient.  (6a) The TrTFL is partly visualized as a thick hypointense band posterior to the talar dome (arrow).  (6b) The AITFL (arrow) and PITFL (arrowhead) are both visible on an axial image through the tibiotalar joint.

 

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Figure 7:

Axial fast spin-echo T2-weighted image approximately 2 cm above the tibial plafond. The interosseous ligament, which is the lower margin of the interosseous membrane, is visible as a thin linear hypointense band extending from the tibia to the fibula (arrow).

 

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Figure 8:

Coronal fat suppressed fast spin-echo proton density-weighted image shows the AITFL as a striated band with an oblique orientation between the anterolateral tibia and the lateral malleolus (arrow). The oblique orientation and craniocaudal extent of the AITFL often requires 2 to 3 axial images to completely assess.

 

 

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Figure 9:

Oblique coronal fast spin-echo proton density-weighted image demonstrates the tibial and fibular attachments of the AITFL on a single image (arrows), which is difficult to obtain with standard axial and coronal imaging planes.

 

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10b
Figure 10:

Contiguous coronal fat suppressed fast spin-echo images in the same patient.  (10a) The PITFL is visible as a striated, triangular structure which is relatively narrow at its fibular insertion(arrowhead) and wider at the tibial attachment (arrows).  (10b) Just anterior to image 10a, a small amount of joint fluid protrudes superiorly into the normal interosseous synovial recess (arrow). The interosseous ligament is the lower margin of the interosseous membrane, and is visible as a transverse bandlike structure at the upper margin of the synovial recess (arrowheads).

 

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Figure 11:

Coronal fat suppressed T2-weighted image in a patient with a tibiotalar effusion. Joint fluid separates the PITFL (arrows) from the more inferior TrTFL (arrowheads). In many patients, these two ligaments are not well delineated from each other due to their proximity.

 

Mechanism of injury and clinical presentation

A variety of mechanisms have been reported for syndesmotic injuries; the most common is thought to be forced external rotation with ankle dorsiflexion and pronation.1 The AITFL is the most commonly torn ligament, and will almost always be torn before the other syndesmotic ligaments.11 Patient symptomatology is similar to other ankle sprains, with the addition of supramalleolar pain and edema.12 Athletes may report pain predominantly in the push-off phase of their gait.5

Imaging

Conventional radiographs are usually the initial imaging test obtained after ankle injury. Widening of the ankle mortise and lateral shift of the talus with respect to the medial malleolus are radiographic signs of syndesmotic diastasis. Fractures of the fibula and distal tibia are commonly associated with syndesmotic injury, and may also be diagnosed on radiographs.1,5 Stress radiographs in external rotation are advocated by some authors, but have been reported by others to demonstrate a high false-negative rate and low interobserver correlation.1,5,8 CT may be useful to detect small cortical fractures which are difficult to visualize on radiographs, and is more sensitive for mild syndesmotic injuries.13

MRI provides excellent soft tissue contrast and direct visualization of the syndesmotic ligaments.9,10,14 MRI criteria for syndesmotic ligament injury are similar to those used for other ankle ligaments. Absence or complete discontinuity of a ligament is consistent with complete tear. Wavy or irregular contour of remaining ligament fibers supports the diagnosis of tear, and increases specificity.9,10,12,14 Thickening or increased signal in the ligament with adjacent edema is compatible with acute sprain. Thickening of the ligament without acute edema may indicate chronic sprain, or healed injury with surrounding fibrosis. Reported sensitivity and specificity of MRI for acute syndesmotic ligament injury is very good in the literature, with sensitivity approaching 100% and specificity ranging from 70% to 94%.9,14 Sensitivity and specificity of noncontrast MRI was reported to be significantly lower in chronic syndesmotic injuries by Kim et al, with sensitivity ranging from 54.2 to 62.5% and specificity of 52.4% to 61.9%.10 Variable enhancement after intravenous contrast has been reported in ligament tears, with some authors reporting increased sensitivity and specificity by utilizing postcontrast imaging, particularly in chronic injuries.9,10

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12b
Figure 12:

Complete tear of the AITFL with interosseous ligament sprain in a 22 year old male after wakeboarding injury.  (12a) Axial fast spin-echo T2-weighted image demonstrates complete AITFL tear. The torn ligament fibers are clumped into a round hypointense object with irregular margins (arrow).  (12b) Coronal fat suppressed fast spin-echo proton density-weighted image in the same patient shows edema extending craniad into the interosseous ligament and interosseous membrane (arrows), indicating sprain.

 

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13b
13c
Figure 13:

Football injury 2 weeks ago in a 26 year old male.  (13a) Axial fast spin-echo T2-weighted image through the tibial plafond demonstrates complete tear of the AITFL (arrow) and partial tear of the PITFL (arrowhead).  (13b) Coronal fat suppressed fast spin-echo proton density-weighted image through the interosseous ligament shows complete tear of the ligament with edema extending superiorly in the interosseous space (arrows). (13c) Coronal fat suppressed fast spin-echo proton density-weighted image through the PITFL again demonstrates high grade partial tear of the ligament at the tibial insertion (arrows).

 

 

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14b
Figure 14:

Football injury in a 19 year old male.  (14a) Axial fast spin-echo T2-weighted image through the tibial plafond. The AITFL (arrow) and PITFL (arrowheads) are both torn with discontinuity, irregular morphology and increased intrasubstance signal.  (14b) Sagittal fat suppressed fast spin-echo T2-weighted image demonstrates a subperiosteal hematoma (arrowheads) just posterior to a bone contusion in the posterior tibia (asterisk).

 

High ankle sprains are often associated with additional ankle injuries and fibular fractures. Brown et. al. found osteochondral lesions of the talar dome in 28%, bone contusions in 24%, and lateral ligament complex tears in 74% of 59 patients with syndesmotic injuries.15 Uys and Rijke observed an inverse correlation between severity of syndesmotic injury and lateral ankle sprains; more severe syndesmotic instability tends to be isolated and not associated with lateral ankle sprains. The authors hypothesized that syndesmotic injuries and lateral ankle sprains are usually caused by different mechanisms of injury.12

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15b
Figure 15:

Football injury in a 26 year old male.  (15a) Axial STIR image in a 26 year old male after football injury shows a complete tear of the AITFL (arrow).  (15b) On the second image obtained inferior to the syndesmosis, a high grade partial tear of the anterior talofibular ligament has also been sustained (arrowhead).

 

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Figure 16:

Axial fast spin-echo T2-weighted image in a 17 year old male after fall 5 days ago demonstrates a complete tear of the AITFL with discontinuity (green arrow), edema in the PITFL consistent with sprain (red arrow), and a nondisplaced posterior malleolar fracture of the distal tibia (arrowheads).

 

Clinical Management

Conservative treatment is generally preferred for stable injuries of the syndesmosis, and initially includes rest, ice and immobilization. This is followed by limited weightbearing with application of joint protective devices such as a walker boot or functional brace. As the patient improves, strengthening and agility exercises may aid return to normal activities and athletic competition.1,5,17

In patients with unstable syndesmotic injury or frank diastasis of the syndesmosis, surgical reduction with placement of trans-syndesmotic screws may be indicated. This is usually followed by casting for 6 weeks and subsequent rehabilitation. Early surgical intervention ensures adequate reduction of the ankle mortise and positions the injured ligaments for optimal healing.1,5,16,18 Delayed surgery (due to initially missed diagnosis, or loss of reduction in a conservatively treated patient) is generally associated with less robust healing.5 Surgical treatment for chronic syndesmotic injuries has been reported to improve symptoms in the majority of patients, with residual pain and dysfunction in 14 to 20%.1,19,20

Ossification along the syndesmotic ligaments with synostosis may develop as a late complication 3 to 12 months after the initial injury.1,21 This can be associated with local pain, but up to 50% of patients with such ossification reported minimal or no symptoms.1,21,22 Surgical excision of painful synostoses has been reported, with relief of symptoms in most patients.1,21

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Figure 17:

Axial T1-weighted image showing ossification of the anterior and posterior syndesmotic ligaments (arrows) in a 31 year old male after previous left ankle syndesmosis injury several years ago.

 

Conclusion

Injury of the distal tibiofibular syndesmosis occurs in a significant minority of ankle sprains, and is associated with increased risk for chronic ankle dysfunction and persistent pain. Early diagnosis and prompt appropriate treatment has been advocated to decrease the likelihood of long-term sequelae. MRI provides excellent visualization of ankle anatomy, allowing accurate diagnosis of ligament abnormalities and any associated osteochondral or tendon injuries. MRI may be especially valuable for early detection of syndesmotic injury in patients with an unclear clinical history, and with equivocal or difficult clinical examinations.

References

1 Williams G, Jones M, Amendola A. Syndesmotic ankle sprains in athletes. Am J Sports Med. 2007;35(7):1197-207. Epub 2007 May 22.

2 Cox J. Surgical and nonsurgical treatment of acute ankle sprains. Clin Orthop 1985;198:118-126.

3 Dunlop M, Beattie T, White G, et al. Guidelines for selective radiological assessment of inversion ankle injuries. Br Med J 1986;293:603-605.

4 Clanton T, Paul P. Syndesmosis injuries in athletes. Foot Ankle Clin N Am 2002;7:529-549.

5 Press C, Gupta A, Hutchinson M. Management of ankle syndesmosis injuries in the athlete. Curr Sports Med Rep. 2009;8(5):228-33.

6 Amendola A, Williams G, Foster D. Evidence-based approach to treatment of acute traumatic syndesmosis (high ankle) sprains. Sports Med Arthrosc Rev 2006;(14):232-236.

7 Bartonicek J. Anatomy of the tibiofibular syndesmosis and its clinical relevance. Surg Radiol Anat 2003;25:379-386.

8 Molinari A, Stolley M, Amendola A. High ankle sprains (syndesmotic) in athletes: Diagnostic challenges and review of the literature. Iowa Orthop J. 2009;29:130-138.

9 Vogl T, Hochmuth K, Diebold T, Lubrich J, Hofmann R, St?ckle U, S?llner O, Bisson S, S?dkamp N, Maeurer J, Haas N, Felix R. Magnetic resonance imaging in the diagnosis of acute injured distal tibiofibular syndesmosis. Invest Radiol 1997;32(7):401-409.

10 Kim S, Huh Y, Song H, Lee S, et al. Chronic tibiofibular syndesmosis injury of ankle: evaluation with contrast-enhanced fat-suppressed 3D fast spoiled gradient-recalled acquisition in the steady state MR imaging. Radiology 2007;242(1):225-235.

11 Rasmussen O. Stability of the ankle joint: analysis of the function and traumatology of the ankle ligaments. Acta Orthop Scand 1985;211:1-75.

12 Uys H, Rijke A. Clinical association of acute lateral ankle sprain with syndesmotic involvement: a stress radiography and magnetic resonance imaging study. Am J Sports Med 2002;30(6):816-822.

13 Taser F, Shafiq Q, Ebraheim N. Three-dimensional volume rendering of tibiofibular joint space and quantitative analysis of change in volume due to tibiofibular syndesmosis diastases. Skeletal Radiol 2006;35:1197-1207.

14 Oae K, Takao M, Naito K, Uchio Y, Kono T, Ishida J, Ochi M. Injury of the tibiofibular syndesmosis: value of MR imaging for diagnosis. Radiology. 2003;227(1):155-161. Epub 2003 Feb 28.

15 Brown K, Morrison W, Schweitzer M, Parellada J, Nothnagel H. MRI findings associated with distal tibiofibular syndesmosis injury. AJR Am J Roentgenol. 2004;182(1):131-6.

16 Park J, McLaurin T. Acute syndesmosis injuries associated with ankle fractures: current perspectives in management. Bull NYU Hosp Jt Dis. 2009;67(1):39-44.

17 Boytim M, Fischer D, Neumann L. Syndesmotic ankle sprains. Am J Sports Med 1991;19:294-298.

18 Egol KA, Pahk B, Walsh M, Tejwani NC, Davidovitch RI, Koval KJ. Outcome after unstable ankle fracture: effect of syndesmotic stabilization. J Orthop Trauma. 2010;24(1):7-11.

19 Beumer A, Heijboer R, Fontijne W, Swierstra B. Late reconstruction of the anterior distal tibiofibular syndesmosis: good outcome in 9 patients. Acta Orthop Scand 2000;71:519-521.

20 Wolf B, Amendola A. Syndesmosis injuries in the athlete: when and how to operate. Curr Opinion Orthop 2002;13:151-154.

21 McMaster J, Scranton P. Tibiofibular synostosis: a cause of ankle disability. Clin Orthop Relat Res 1975;111:172-174.

22 Whiteside L, Reynolds F, Elisasser J. Tibiofibular synostosis and recurrent ankle sprains in high performance athletes. Am J Sports Med 1978;6:204-208.