The posterior malleolus approaches clock: a method of guiding incision choice for fragment specific fixation

S. Gandham, G. Millward, A. Molloy, L. Mason

¹Aintree University Hospital, NHS Foundation Trust, Liverpool, United Kingdom

²University of Liverpool, Liverpool, United Kingdom 

Winner of the BOFAS 2019 Best Poster Prize

Aim: The aim of this study was to determine the most appropriate approach for fixation of each type and fragment of posterior malleolar fractures.

Materials and methods: A retrospective analysis of a prospectively collected database was performed on 141 posterior malleolar fractures. On the CT scan axial slice, a clock face was drawn using the posterolateral corner of the tibia as the centre and the Achilles tendon as the 6 o'clock axis. A box was then drawn from the fracture plane, with 90-degree lines corresponding to the medial line (ML) and lateral line (LL) extremity of the fracture and a central line (CL) (i.e. orthogonal central plane, for optimum screw placement). It was recorded where the ML, LL and CL exited the clock face. All fracture patterns were further assessed by both senior authors regarding their choice of approach based on CL and all variances resolved by discussion.

Results: The LL was equivalent across the groups (except for the 2B medial fragments), indicating a consistent posterolateral corner fragment throughout the posterior malleolar sub types (p=.25). The medial aspect (ML) of the type 1, type 2A and posterolateral fragments of type 2B were equivalent. The posterolateral approach was determined to be the most appropriate approach to access these posterolateral fragments. The ML of type 3 fractures was significantly more medial than the other type 1 and 2A (p< .05), and almost all could be appropriately accessed through the posteromedial approach. The majority of type 2B fractures (2/3rds) were determined to be best accessed through a combined posterolateral and medial posteromedial approaches.

Conclusion: We conclude that the extent of each subtype of posterior malleolar fractures are anatomical consistent. To fully expose each fracture, differing incisions are necessary and can be accurately predicted by CT classification and the clock face method.

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