From Hunterian to Hunterian: the posterior malleolar fracture

BACKGROUND: The posterior malleolar fracture (PMF) is now understood through three-dimensional imaging and mechanism-based classification, yet this understanding is not new. We argue that its central mechanism (rotation of an axially loaded talus within the ankle mortise) was inferred by Bonnin three-quarters of a century ago, obscured by an era of radiographic, size-based description, and later confirmed and made visible by computed tomography (CT). This continuity is frequently overlooked in the wider literature. METHODS: We present a narrative review of the primary historical literature alongside contemporary CT-based and cadaveric studies. RESULTS: Bonnin's cadaveric experiments showed that a rotating, axially loaded talus behaves as a wedge within the mortise, splitting the posterior tibial margin (the injury we now term a rotational pilon fracture) and he held that damage to the plafond, not the size of the fragment, determined the prognosis. Attention later shifted to the proportion of articular surface involved - a quantity poorly measured on radiographs and divorced from mechanism. CT has since reintroduced the mechanism in living patients: the Mason-Molloy classification describes three pathomechanical types that confirm and refine Bonnin's observations, and management has moved from size thresholds to classification-guided fixation. CONCLUSIONS: Bonnin and Mason, two Hunterian Professors separated by more than half a century, performed essentially the same investigation with the tools available to them and reached the same conclusion. Recognising that the modern classification visualises a mechanism Bonnin had already inferred (rotation of a loaded talus) restores a continuity the wider literature has largely missed.