A 20-year-old otherwise healthy woman injured her right foot in a fall while skateboarding 1 week ago. She was seen at the emergency room where x-rays of the foot were obtained (Fig. 5–56A–C). She was splinted and referred to your orthopaedic clinic. She has moderate edema of the right foot and tenderness through the midfoot and slight forefoot abduction compared to the contralateral foot.

Figure 5–56 A: AP radiograph of the foot. B: Oblique radiograph of the foot. C: Lateral radiograph of the foot.

Which of the following is the LEAST likely sequela of this injury?

1. Development of a pes cavus deformity

2. Avascular necrosis

3. Posttraumatic arthrosis

4. Loss of subtalar motion

Discussion

The correct answer is (A). This patient has sustained what Sangeorzan described as a type 3 navicular body fracture resulting in comminution of the lateral pole of the tarsal navicular. The loss of support of the lateral pole of the navicular has allowed the forefoot to abduct, making a cavus deformity unlikely. The amount of articular surface of the navicular limits its blood supply to dorsal branches fed by the dorsalis pedis artery and plantar branches supplied by the medial plantar branch of the posterior tibial artery. This anatomy makes avascular necrosis a concern when treating navicular fractures. The comminution at the talonavicular joint predisposes these fractures to development of posttraumatic arthrosis and subsequent loss of subtalar motion because of the intimate coupling of the talonavicular joint with subtalar motion.

A CT scan is obtained of the foot (Fig. 5–57A–C).

Figure 5–57 A: Axial CT of the foot. B: Sagittal CT of the foot. C: Coronal CT of the foot.

What is the recommended treatment for this fracture?

1. Short-leg cast and protected weight bearing

2. Open reduction with internal fixation of the navicular fracture

3. Fracture boot and functional rehabilitation

4. Primary fusion of the talonavicular joint

Discussion

The correct answer is (B). The CT scan shows comminution with displacement of the fragments of the lateral pole of the navicular. Closed treatment would be reserved for nondisplaced fractures, typically Sangeorzan type 1 or some stress fractures of the navicular. A removable boot would not offer adequate support for this fracture, and if treated closed, motion should not be instituted until radiographic union is seen. Primary talonavicular arthrodesis may be the salvage procedure needed in severe fractures when a sufficient reconstruction of the articular surface or restoration of length cannot be obtained. However, in a young and active individual, every attempt to reconstruct the joint surface, support length (which may require bone grafting), and maintain function should be made (Fig. 5–58A and B).

Figure 5–58 A: Postoperative AP radiograph showing plate and screw fixation. B: Lateral postoperative radiograph showing internal fixation and autograft harvest site from calcaneal tuberosity.

Objectives: Did you learn...?

Use Sangeorzan classification of navicular fractures? Describe the vascular supply to the tarsal navicular? Describe the coupling of talonavicular and subtalar motion?