Accessory Navicular Bone

Definition

Definition of Accessory Navicular Bone
An accessory navicular bone is an accessory bone of the foot that occasionally develops abnormally in front of the ankle towards the inside of the foot. This bone may be present in approximately 2.5% of the general population and is usually asymptomatic. When it is symptomatic, surgery may be necessary.

Symptoms

Symptoms of Accessory Navicular Bone
Adolescence is a common time for the symptoms to first appear. This is a time when bones are maturing and cartilage is developing into bone. Sometimes, however, the symptoms do not occur until adulthood.

Causes

Causes of Accessory Navicular Bone
Review the causal information about the various more general categories of medical conditions:

1. Musculoskeletal conditions
2. Bone or skeletal conditions
3. Foot conditions
4. Lower limb conditions
5. Lower leg conditions

Diagnosis

Diagnosis of Accessory Navicular Bone
To diagnose accessory navicular syndrome, the foot and ankle surgeon will ask about symptoms and examine the foot, looking for skin irritation or swelling. The doctor may press on the bony prominence to assess the area for discomfort. Foot structure, muscle strength, joint motion, and the way the patient walks may also be evaluated.

X-rays are usually ordered to confirm the diagnosis. If there is ongoing pain or inflammation, an MRI or other advanced imaging tests may be used to further evaluate the condition.

Clinical Presentation

Clinical Presentation of Accessory Navicular Bone
Many people have accessory (“extra”) naviculars - a prominent extra bone extending form the navicular bone. Most accessory naviculars are completely asymptomatic. However, some individuals will develop pain on the inside of their hindfoot. This pain occurs either from the prominent extra bone rubbing against a shoe; from irritation at the fibrous junction where the accessory bone meets the regular navicular; or for both of these reasons. Often individuals will be asymptomatic for years until a new pair of shoes or a change in their activity level precipitates symptoms. The accessory navicular itself typically develops during adolescence when the two areas of the navicular bone fail to fuse together.

Treatment

Treatment of Accessory Navicular Bone
The goal of non-surgical treatment for accessory navicular syndrome is to relieve the symptoms. The following may be used:

1. Immobilization. Placing the foot in a cast or removable walking boot allows the affected area to rest and decreases the inflammation.
2. Ice. To reduce swelling, a bag of ice covered with a thin towel is applied to the affected area. Do not put ice directly on the skin.
3. Medications. Oral nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be prescribed. In some cases, oral or injected steroid medications may be used in combination with immobilization to reduce pain and inflammation.
4. Physical therapy. Physical therapy may be prescribed, including exercises and treatments to strengthen the muscles and decrease inflammation. The exercises may also help prevent recurrence of the symptoms.
5. Orthotic devices. Custom orthotic devices that fit into the shoe provide support for the arch, and may play a role in preventing future symptoms.