Navicular Stress Fractures

Akash Gupta

Martin O’Malley

Introduction

Navicular stress fractures often present with vague complaints of pain on the dorsal foot and even pain in the ankle. The presentation is usually insidious in nature.
Symptoms tend to improve with rest or immobilization but recur once activities are resumed.
The findings from the physical examination are often impressive, and x-ray results are typically negative. As such, the diagnosis is often delayed.
Patients with long second metatarsals and short first metatarsals are at particular risk.
Patients with a cavus foot and metatarsus adductus are also at risk.
Patients that have limited ankle dorsiflexion due to impingement have higher contact stresses with axial loading, which can predispose to stress fractures. Thus, athletes with repetitive axial loads, such as basketball and football players or track and field athletes, are at risk.
These patients often have osteophytes over the dorsum of the talonavicular joint.

Classification

Type I: fracture in the dorsal cortex (see Figure 22-1)
Type II: fracture extends from dorsal cortex into navicular body (see Figure 22-2)
Type III: complete fracture through both cortices (see Figure 22-3)

Figure 22-1. Type I navicular fracture.

Figure 22-2. Type II navicular fracture.

Figure 22-3. Type III navicular fracture.

Imaging

X-rays: Routine weight-bearing radiographs (anteroposterior, lateral, and oblique) are typically the initial imaging modality of choice. However, these should not be used in isolation because radiographs have been shown to have very low sensitivity for navicular stress fractures. Moreover, most navicular fractures do not involve the plantar cortex, making them difficult to identify on radiographs until osteoclastic resorption has occurred. Rather, these images should be used to rule out other potential causes of medial foot and ankle pain, such as malalignment, talar neck spurring, or capsular avulsions (see Figure 22-4).
Triple-phase bone scan: Given their high sensitivity and high positive predictive value in identifying these fractures, bone scans may be used to screen for navicular stress fractures. Despite the high sensitivity, a positive bone scan is not specific for this navicular stress fracture. Moreover, bone scans lack anatomic resolution and do not provide an accurate depiction of the specific fracture pattern. As such, this imaging modality has largely been replaced by magnetic resonance imaging (MRI).

Figure 22-4. Anteroposterior and lateral radiographs demonstrating dorsal spurring of the talonavicular joint.

MRI: MRI is considered the gold standard because it is the best at detecting bone edema and stress reaction, which may occur before a stress fracture. Navicular stress reactions present with similar symptoms as stress fractures, but lack an obvious fracture line on computed tomography (CT). By detecting such stress reactions early, steps may be taken to prevent the stress reaction from progressing into a full-blown stress fracture (see Figure 22-5). MRI has the additional advantage of avoiding radiation exposure.