Complete Medial Dislocation of the Tarsal Navicular without Fracture: Report of a Rare Injury

Complete dislocation of the tarsal navicular, without fracture of the navicular, is an uncommon injury. A review of the published data revealed only 15 previous reported cases. The rarity of this injury can be attributed to the rigid bony and ligamentous support surrounding the navicular, which usually undergoes fracture and dislocation rather than pure dislocation of the navicular. The mechanism and appropriate treatment of this injury remains unclear. In the present report, we describe the case of a 29-year-old male who sustained complete dislocation of the tarsal navicular, without fracture of the navicular, along with fractures of the cuboid and calcaneus, when he was involved in a motor vehicle collision. The proposed mechanism of injury in this case was that of a pronation-abduction force applied to the midfoot, resulting in a transient midtarsal dislocation and disruption of the ligamentous support of the navicular, with medial dislocation of the navicular when the midtarsal dislocation was reduced. The anterolateral calcaneus and cuboid fractures were likely from an avulsion injury through the bifurcate ligament. The patient was treated successfully with closed reduction and Kirschner wire fixation of the navicular combined with application of a spanning external fixator. The pins and external fixator were removed at 7 weeks postoperatively, and the navicular was stable at that time. The patient was lost to follow-up shortly thereafter.