What is your diagnosis?

Distal tibiofibular syndesmosis disruption resulting in an unstable mortise (Image 2). 

• Pearl: Widening of the mortise indicates a serious ligamentous disruption of medial ligaments (Image 2, blue arrow) and the distal syndesmosis (Image 2, red arrow). In a normal ankle, there should be a symmetrical clear space around the talus and the tibia should slightly overlap the fibula (Image 3). 

Image 2, 3. Image 2 courtesy of Radswiki, Radiopaedia.org, rID: 11592; Image 3 courtesy of Andrew Murphy, Radiopaedia.org, rID: 48079

Other views of the ankle do not reveal additional pathology. What other diagnosis should you evaluate for?

Proximal ⅓ fibular fracture (Maisonneuve fracture) - see Image 4. Always remember to image the full length of the tibia and fibula to assess for associated fractures; these can be easily missed if not careful.[1]

Image 4. Associated fracture of the proximal fibula. Case courtesy of Radswiki, Radiopaedia.org, rID: 11592

• Pearl: Maisonneuve, a French surgeon, described this injury in which the fibular fracture would occur only if the medial malleolus or deltoid ligament failed first followed by rupture of the tibiofibular syndesmosis [1].

• Pearl: These injuries are even worse than they appear on x-ray, as significant soft tissue and ligamentous injuries occur with this fracture pattern [1].

What is the mechanism of injury of the additional diagnosis?

A forceful pronation-external rotation injury as classified by Lauge Hansen [2]. It can also be caused by supination-external rotation.

What physical exam findings are expected of the additional diagnosis?

Tenderness to palpation of the proximal fibula and positive squeeze test.

• Pearl: Evaluate the common fibular or peroneal nerve as it wraps around the proximal fibula. Sensory (lateral lower leg) or motor deficits (ankle dorsiflexion or foot eversion) should raise concern.

What is the management in the ED?

Reduction and stabilization with stirrup and posterior splint. Reduction can be achieved with internal rotation to allow more appropriate realignment of the mortise and restoration of fibular length. These fractures tend to fall out laterally post-reduction, so be sure to form your mold accordingly. 

When do you consult Orthopedics?

Neurovascular compromise, open fracture, or inability to achieve proper alignment. Management is institution dependent, but the majority will advocate for operative fixation of the syndesmosis and ligamentous repair [1].