Accessory navicular bone

Alternate names

Accesory navicular syndrome

Definition

An accessory navicular bone is an extra bone or piece of cartilage located in the middle of the foot near the navicular bone, the bone that goes across the foot near the instep. It is present from birth (congenital) and is a common trait.

File:Accessory and cornuate navicular bone on dorsoplantar X-ray - annotated.jpg

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File:Accessory Navicular 02.jpg

Epidemiology

The reported incidence differs among populations and ethnic groups, and they are mostly reported as incidental findings in anatomical and imaging studies, estimated to occur in approximately 2 to 20% of the general population.

Cause

• An accessory navicular bone is typically considered to be a developmental abnormality present from birth (congenital).
• The exact cause of accessory navicular bone is unknown; however, it may be related to an incomplete joining (fusion) of bones and connective tissue during development and/or an abnormal separation of affected bones and connective tissue.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

Inheritance appears to be autosomal dominant.

Types

There are three types of accessory navicular bones which are differentiated by location, size, and tissues involved (bone and/or cartilage).

Signs and symptoms

• While some individuals with an accessory navicular bone never experience symptoms, others can develop a painful condition, sometimes referred to as accessory navicular syndrome.
• This occurs when the bone and/or connective tissue are aggravated.
• This can be caused by injury to the affected region, chronic irritation from from shoes or other sources, and excessive activity or overuse.
• Symptoms of accessory navicular syndrome usually occur around adolesence and may include development of a painful, red or swollen bump on the midfoot (inner side of the foot above the arch).

Diagnosis

• 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.

Treatment

• If the accessory navicular bone is causing symptoms, activities may be restricted and a softer shoe may be recommended until the symptoms go away.
• If the symptoms persist, a specially and carefully made shoe support may be tried.
• For people with accessory navicular bone who experience severe symptoms, surgery may be considered to remove the bony growth.
• Other treatments may include medications such as nonsteroidal anti-inflammatories (NSAIDs), immobilizing the area with a cast or boot, and physical therapy.

NIH genetic and rare disease info

• NIH info on Accessory navicular bone

Accessory navicular bone is a rare disease.