Biomechanical Effect of Ankle Ligament Injury in AO Type 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 a plate created by finite element analysis modeling and loading applied to ligament rupture models that may accompany this fracture.

Methods: A finite element model consisting of three-dimensional fibula, tibia, foot bones, and ankle ligaments was designed to investigate the effects of ligament injuries accompanying plate-detected AO type 44B2.1 fractures on fracture detection, fixation material, and ankle joints. Then, the results were evaluated by modeling ligament rupture in six different ways.

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

Conclusions: In the finite element modeling of AO type 44B2.1 fractures detected with plate, the importance and potential effects of often-overlooked ankle ligament injuries are pointed out. Note 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.