Posterior malleolus fractures, also known as Volkmann fractures, are fractures of the posterior segment of the tibial plafond and a common occurrence in the setting of bimalleolar or trimalleolar ankle fractures.
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Epidemiology
Posterior malleolar fractures occur in up to 46% of type Weber B or C fracture-dislocations and are rarely isolated 1.
Pathology
Mechanism
Posterior malleolus fractures can occur as a result of the following mechanisms 2,3:
supination and adduction
supination and external rotation
pronation and external rotation or abduction
They are seen in the context of medial malleolar and infrasyndesmotic, transsyndesmotic or suprasyndesmotic fibular injuries.
Classification
Different classification systems have been proposed, basically differentiating between the following 1,4,5:
small and extra-incisura fragments
posterolateral fragments
fragmented posterior malleolus fractures with medial extensions
larger posterolateral fragments
Radiographic features
Initial evaluation of an ankle injury is done with ankle anteroposterior, lateral and mortise views. Further imaging methods include CT for obtaining more detailed information or rarely MRI 1.
Plain radiograph
The posterior malleolus fracture is best appreciated on the lateral radiograph of the ankle, evident as a bony discontinuity often associated with an articular step-off.
On the anteroposterior radiograph of the ankle, a posterior malleolus fracture might be evident as a double contour of the medial malleolus if the latter is involved. Another possible indicator might be a vertical course of an associated medial malleolar fracture.
CT
True fragment size and geometry, as well as displacement, can be nicely visualized and assessed with axial and sagittal planes, which can be combined with 3D reconstructions, CT is also helpful for exact fracture classification 1.
MRI
MRI can supply additional information regarding syndesmosis injury or concerning possible associated chondral lesions or tendon injury 1. It is important to assess for posterior inferior tibiofibular ligament integrity.
Radiology report
The radiological report should include a description of the following:
the complete extent of the fracture including medial malleolar and fibular fractures
location of the fragment (posteromedial, posterolateral)
the extent of involvement of the articular surface
simple, fragmentary, intercalated fragments
involvement of the fibular notch
talar subluxation
Treatment and prognosis
Open reduction and internal fixation are usually performed after concomitant medial and lateral malleolar fractures or injuries have been reduced and fixed under the following conditions 1:
significant posterior malleolar fragment size or articular surface (20-25%) involved
posterior talar subluxation or other signs of tibiotalar instability
posterolateral injury with concomitant fibular fractures for better restoration of the syndesmotic structure 1,4
It can be performed by anteroposterior screw fixation after reduction and temporary K-wire stabilization or with posterolateral, posteromedial or combined approaches including a small buttress plate in case of larger fragments 1,5.
History and etymology
The first description of a fracture of the posterior edge of the distal tibia in an ankle fracture-dislocation was by the English surgeon Henry Earle (1789-1838) 6 in 1828 1.
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