Defining A Safe Zone For Percutaneous Screw Fixation Of The Posterior Malleolus

Abstract

Category: Trauma Introduction/Purpose: Fixation of the posterior malleolar fragment of an ankle fracture confers stability. Not all posterior fragments are displaced, necessitating open reduction. We hypothesised that a safe anatomic corridor is possible for percutaneous screw fixation in some fracture variants. We conducted an anatomic study to determine if percutaneous fixation was possible and safe. This anatomic assessment of significant structures at the posterior ankle, combined with cadaveric dissection following placement of screw tracts shows that percutaneously fixing the posterior malleolus is achievable in medially positioned fragments. Methods: Multiple percutaneous Kirschner wires were passed into a cadaveric ankle specimen at reproducible anatomic points. The wires were passed into typical locations for posterior malleolus fixation. The specimen was dissected and all wires threatening significant structures were removed. A single safe medial passage was identified. The surface anatomy landmarks for the single safe wire was recorded. Multiple (6) cadaveric specimens were further wired via an entry point using only the surface anatomy landmarks previously determined to be safe. These were dissected to confirm the presence of a safe zone for percutaneous wiring of the posterior malleolus. Image intensifier was used to confirm adequate placement of the wire in the posterior malleolus. Results: A safe medial zone for percutaneous fixation of the posterior malleolus was consistent; this was successfully replicated utilising surface anatomy alone. The entry point for safe percutaneous fixation was found to be 1 cm proximal to the tip of the medial malleolus and immediately lateral to the tendo-achilles. Conclusion: A safe passage for percutaneous screw placement for medially located posterior malleolar fragments (Haraguchi I/II) was identified. A safe zone for percutaneous fixation of the posterior malleolus has been newly defined.