Acute navicular fractures can be divided into avulsion and axial compression fractures.
Avulsion fractures of the dorsal lip of the navicular account for about 50% of navicular fractures. The mechanism of injury is acute foot plantar flexion in which the talonavicular ligament and joint capsule pull off the proximal, dorsal aspect of the navicular. Treatment is usually conservative, unless a major fragment of the articular surface has been avulsed. In this instance, open reduction and internal fixation may be performed.
Fractures of the navicular tuberosity result from acute eversion of the foot, leading to increased tension in the posterior tibialis tendon and spring ligament, and, subsequently, an avulsion fracture. With a severe eversion force, an associated lateral column impaction injury may occur. An accessory navicular can be distinguished from an acute fracture by a smooth, regular line of separation or a rounded appearance to the accessory bone and is bilateral in up to 90% of individuals. Minimally displaced fractures may be treated with casting, while displaced fractures require open reduction and internal fixation.
Axial Compression Fractures
Fractures of the navicular body are the most severe, as the talonavicular and naviculocuneiform joints are involved. In these high energy injuries, an axial force causes the talar head to act as a wedge and crushes the navicular between the talus and the cuneiforms. The talonavicular, naviculocuneiform, and calcaneocuboid joints all may be damaged. The treatment of these injuries involves anatomically reducing the talonavicular and naviculocuneiform joints using an anteromedial approach between the anterior and posterior tibial tendons. An external fixator can be placed medially to distract the medial column during reduction of the navicular joint surfaces. Bone graft is used to fill any central defects in the navicular body after elevation of the joint surfaces. Fixation of the fracture fragments with lag screws and stabilization of the injured joint capsules with K-wires is then performed.
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