Diagnosis

Infrasyndesmotic lateral lesion, with fracture of the medial malleolus (AO/OTA 44A2) 

print

Infrasyndesmotic fractures (AO/OTA Type 44A) occur with the foot supinated and an adduction force applied to the talus, causing the lateral structures to fail in tension.

If the talus continues to tilt, it causes a shearing compression fracture of the medial malleolus. These are classified as AO/OTA 44A2 fractures, and correspond to the supination-adduction fractures stage II in the Lauge-Hansen classification.

Complete radiological evaluation (AP, lateral and AP with internal rotation) is crucial for correct classification and decision making.

Options
1. Rupture of the lateral collateral ligaments (AO/OTA 44A2.1) 
2. Avulsion of the tip of the lateral malleolus (AO/OTA 44A2.2) 
3. Transverse fracture of the lateral malleolus (AO/OTA 44A2.3) 

1. Rupture of the lateral collateral ligaments (AO/OTA 44A2.1) 

Rupture of the lateral collateral ligaments (AO/OTA 44A2.1)

Rupture of the lateral collateral ligaments (AO/OTA 44A2.1)

If the lateral malleolus is intact, and the lateral injury involves a rupture of the lateral collateral ligaments (the calcaneo-fibular ligament and the anterior and posterior talo-fibular ligaments), with a medial malleolar fracture (oblique or vertical), this is classified as an AO/OTA 44A2.1 fracture.

Radiograph taken from Orozco R et al, (1998) Atlas of Internal Fixation. Used with kind permission.

2. Avulsion of the tip of the lateral malleolus (AO/OTA 44A2.2) 

Avulsion of the tip of the lateral malleolus (AO/OTA 44A2.2)

Avulsion of the tip of the lateral malleolus (AO/OTA 44A2.2)

If the lateral injury involves an avulsion fracture of the tip of the lateral malleolus, with a medial malleolar fracture (oblique or vertical), this is classified as an AO/OTA 44A2.2 fracture.

In these fractures, the superomedial corner of the talus may cause, not only a high oblique or vertical medial malleolar fracture, but also an impaction fracture of the “medial corner” of the tibia, at the junction of its horizontal joint surface (plafond) and the medial malleolar joint surface (see x-ray for 44A2.3 fractures). The impacted “corner” fragment will need to be reduced, prior to reduction and fixation of the medial malleolus.

Third radiograph taken from Orozco R et al, (1998) Atlas of Internal Fixation. Used with kind permission.

3. Transverse fracture of the lateral malleolus (AO/OTA 44A2.3) 

Transverse fracture of the lateral malleolus (AO/OTA 44A2.3)

Transverse fracture of the lateral malleolus (AO/OTA 44A2.3)

Transverse fracture of the lateral malleolus (AO/OTA 44A2.3)

Transverse fracture of the lateral malleolus (AO/OTA 44A2.3)

If the lateral injury involves a transverse fracture of the lateral malleolus, with a medial malleolar fracture (oblique or vertical), this is classified as an AO/OTA 44A2.3 fracture.

In these fractures, the superomedial corner of the talus may cause, not only a high oblique or vertical medial malleolar fracture, but also an impaction fracture of the “medial corner” of the tibia, at the junction of its horizontal joint surface (plafond) and the medial malleolar joint surface. This is effectively a “split depression” injury, analogous to that of the tibial plateau. The impacted “corner” fragment will need to be reduced, prior to reduction and fixation of the medial malleolus.