Tarsal Navicular Fractures

Excerpt

Fractures of the tarsal navicular bone are most commonly the result of either traumatic injury or undue stress, with the latter having a higher incidence in younger individuals and athletes. Even though midfoot fractures are relatively uncommon injuries, tarsal navicular stress fractures represent up to one-third of all stress fractures. These fractures are at high risk of nonunion and osteonecrosis owing to the navicular bone’s tenuous blood supply as well as the inherent complexity of the joint. These fractures often require surgical intervention, though they can be treated conservatively in some cases.

The navicular is a wedge-shaped bone articulating with the talus, calcaneus, the three cuneiform bones, and the cuboid. The bone’s major oblique axis lies dorsoplantar and lateromedial, with its base situated dorsolaterally, and its apex plantar medial.

Posteriorly, the navicular has a biconcave surface which articulates with the head of the talus. Anteriorly, the navicular has plantar concavity, with there being three articular surfaces. The largest of these surfaces is found medially with a convex surface, articulating with the medial cuneiform. The navicular tuberosity, found medially, is the insertion site for the posterior tibial tendon. Considering the large number of articulations found on the various surfaces of the navicular, a large portion of the bone is covered in articular cartilage.

The dorsal aspect of the navicular receives vascular supply by the medial tarsal branches of the dorsalis pedis artery, along with branches of the lateral tarsal artery. Supplying the medial plantar aspect of the navicular is a branch of the tibialis posterior artery. Some literature suggests a zone of avascularity from the central third to the distal cortex of the navicular, which may contribute to the avascular necrosis sometimes associated with these fractures.

The tarsal navicular is an essential component of the Chopart joint, which itself consists of the talonavicular and calcaneocuboid joints. Both of these joints are crucial for inversion and eversion of the foot.