Posterior malleolar fractures occur in up to 46% of type Weber B or C fracture-dislocations and rarely isolated 1.
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.
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
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.
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 can supply additional information in regard to the anterior tibiofibular ligament or with respect to possible associated chondral lesions or tendon injury 1.
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)
- 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.
- 1. Bartoníček J, Rammelt S, Tuček M, Naňka O. Posterior malleolar fractures of the ankle. (2015) European journal of trauma and emergency surgery : official publication of the European Trauma Society. 41 (6): 587-600. doi:10.1007/s00068-015-0560-6 - Pubmed
- 2. Tartaglione JP, Rosenbaum AJ, Abousayed M, DiPreta JA. Classifications in Brief: Lauge-Hansen Classification of Ankle Fractures. (2015) Clinical orthopaedics and related research. 473 (10): 3323-8. doi:10.1007/s11999-015-4306-x - Pubmed
- 3. Solan MC, Sakellariou A. Posterior malleolus fractures: worth fixing. (2017) The bone & joint journal. 99-B (11): 1413-1419. doi:10.1302/0301-620X.99B11.BJJ-2017-1072 - Pubmed
- 4. Haraguchi N, Haruyama H, Toga H, Kato F. Pathoanatomy of posterior malleolar fractures of the ankle. (2006) The Journal of bone and joint surgery. American volume. 88 (5): 1085-92. doi:10.2106/JBJS.E.00856 - Pubmed
- 5. Mason LW, Kaye A, Widnall J, Redfern J, Molloy A. Posterior Malleolar Ankle Fractures: An Effort at Improving Outcomes. (2019) JB & JS open access. 4 (2): e0058. doi:10.2106/JBJS.OA.18.00058 - Pubmed
- 6. Henry Earle. Br Foreign Med Rev. 1838 Apr;5(10):627–8. PMCID: PMC5591690.