Lesson

Navicular

Navicular fractures pose a high risk for long-term pathology and are associated with a poor prognosis if not properly treated. The navicular is the keystone bone of the medial column of the foot with several articulations and a high degree of inherent stability. Navicular stress fractures are strongly associated with sports that involve sudden changes of direction, jumping and sprinting. Like fractures of the base of the fifth metatarsal, they require special consideration as they are hard to diagnose and often challenging to treat. They typically originate on the dorsal bony surface and can progress to a bicortical fracture. Navicular stress fractures represent up to 15% of all sports-related stress fractures. Since there are often only very minimal local signs (pain, swelling, discoloration, ROM, strength) and since the onset of the pain is typically insidious, the diagnosis is often delayed. A high index of suspicion is needed.

 

History

Athletes with a navicular stress fracture typically have an insidious onset of diffuse foot and ankle pain. As the symptoms are often vague, a high index of suspicion is needed.

 

Examination

A helpful, provocative and fairly sensitive diagnostic test is to find the “N spot”. To do so, locate the talonavicular joint by inverting and everting the foot and then palpate the dorsal proximal portion of the navicular. Local tenderness refers to a positive test. Other signs suggestive of a stress fracture (for example, the hop test) are also useful.

 

Investigation

Acute navicular fractures may be seen on plain films, while navicular fractures rarely are. Increased uptake on a bone scan or MRI is diagnostic. CT scans can be used to define an acute fracture or to grade a stress injury. This grading may give some prognostic information based on the extent of the fracture. This ranges from a break in the dorsal cortex only to a complete fracture.

Click on the following images to view examples of navicular stress fractures.

  • Navicular stress fracture (axial)

    Note the florid oedema within the navicular bone

  • Navicular stress fracture (coronal)

    Observe the fracture line extending through two cortices on this T1 weighted image

  • Navicular stress fracture (Saggital)

    Again observe the extensive bone oedema within the navicular.

  • Navicular stress fracture (CT)

    CT can define the fracture orientation more effectively than MRI

  • N-Spot

    Tenderness over the N-spot should make the clinician suspicious of a navicular stress injury

Treatment

Navicular fractures can be managed non-operatively or may be treated with surgical fixation. Six weeks of non-weight-bearing rest is considered to be important for the treatment of these stress injuries. There is evidence of good outcomes for both treatment modalities. If surgery is contemplated, this is usually done using a percutaneous screw. It is suggested that the athlete remains non-weight-bearing for six weeks following surgery. Surgery may be considered when the fracture extends into the body of the navicular – or if two cortices are involved.