Anatomy of the Insertion of the Posterior Inferior Tibiofibular Ligament and the Posterior Malleolar Fracture

Abstract

Category: Ankle Introduction/Purpose: The treatment of posterior malleolar fractures is developing. Our previous study on the anatomy of the posterior malleolar fracture identified only 49% of rotational push off fractures of the posterior malleolus had syndesmotic instabilities. This was against general thinking that fixation of such a fragment would stabilize the syndesmosis. Our aim in this study was to identify the extent of the posterior inferior tibiofibular ligament insertion on the posterior tibia and its relation to push off fractures. Methods: We examined 10 cadaveric lower limbs that had been preserved for dissection at the Human Anatomy and Resource Centre at Liverpool University in a solution of formaldehyde. The lower limbs were carefully dissected to identify the ligamentous structures on the posterior aspect of the ankle. Results: In all specimens, the tibial insertion of the PITFL encompassed 1/3 of the distal posterior tibia. In addition, the posterior intermalleolar ligament inserted onto the posterior tibia just medial to the tibialis posterior groove. Thus a rotational push off fracture would only cause syndesmotic injury if greater than a 3 rd of the posterior tibia was injured or occurred in combination with a ligamentous injury. This is in keeping with the clinical findings of only 49% syndesmotic instabilities with Haraguchi type 1 posterior malleolar fractures. Conclusion: Haraguchi type 1 posterior malleolar fractures (less than a 3 rd of the width of the posterior tibia) are unlikely to cause syndesmotic instabilities without the addition of a ligamentous injury.