Biomechanical effect of ankle ligament injury in AO 44B2.1 lateral malleolus fractures after lateral plate fixation: A finite element analysis.

BACKGROUND: Distal fibula fractures at the ankle level are common and are usually accompanied by ligament injuries. This study aims to evaluate the effects of ankle ligament ruptures on ankle joints, fracture instability, and plate stress after distal fibula fracture fixed with plate created by finite element analysis (FEA) modeling and loading applied to ligament rupture models that may accompany this fracture.

METHODS: A finite element model consisting of 3-D (3D) fibula, tibia, foot bones, and ankle ligaments was designed to investigate the effects of ligament injuries accompanying plate-detected Arbeitsgemeinschaft für Osteosynthesefragen (AO 44B2.1)-type fractures on fracture detection, fixation material, and ankle joints. Then, the results were evaluated by modeling ligament rupture in 6 different ways.

RESULTS: In the modeling where the deltoid and the talofibular ligament are broken together, instability is the highest in the ankle (2.31 mm) and fracture line (0.15 mm). In our study, the rupture of the tibiofibular anterior and posterior ligaments associated with syndesmosis caused less instability in the fracture and ankle than the single rupture models of both the deltoid and the talofibular ligament.

CONCLUSIONS: In the finite element modeling of AO 44B2.1-type fractures detected with plate, the importance and potential effects of often overlooked ankle ligaments are pointed out shown. It is important to keep in mind that when treating ankle injuries, the ankle should be treated as a whole, with both bone and soft tissue. In some cases, the fracture may represent the visible tip of the iceberg.