An accessory navicular is an extra bone or cartilage located on the center of the inside of the arch. This bone is present at birth and typically does not present any issues until the area is strained, such as with a twist or fall. The accessory bone lies just beside the navicular bone, which is where a tendon attaches that aids in maintaining arch height, as well as plantarflexion and inversion (down and inward motion) of the foot. Therefore, with a twisting fall or sprain this area is often injured. Accessory navicular syndrome is the result of irritation or inflammation to the surrounding tissues/bone within that tendon.
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Symptoms
Typical presentation of navicular syndrome is a non-painful bump on the central inner aspect of the foot. Presentation after injury or with overuse may include pain and swelling to the inner ankle and inner foot, close to the ankle. The pain begins at the “bump” on the inner side of the foot or insertion point of the posterior tibialis tendon. The pain increases with inversion and eversion. People with navicular syndrome may be unable to rise on their tiptoes on that foot. Vague pain or throbbing to the midfoot and arch during or after periods of activity is a common finding.
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Causes
The cause of the pain associated with an accessory navicular is most commonly due to a trauma to the area whether it be a fall, slip, twist or sprain. The accessory navicular can be present medially to the navicular without attachment, or with a cartilaginous attachment or with a full bone fusion to the navicular. There are no particular genetic features that determine the presentation of the accessory navicular. Overuse or ill-fitting footwear can also contribute to accessory navicular syndrome.
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Treatment
The initial treatment for navicular syndrome includes a medial heel wedge in shoes or custom orthotics, which can be dispensed following evaluation by a Pedorthist. Ensuring that footwear provides stability as well as moderate medial arch height and responsive cushioning will also aid in resolving the condition. In addition to a heel wedge or orthotic evaluation, medications such as non-steroidal anti-inflammatory will help. Rest and icing after initial presentation can help to reduce inflammation to the tendon, however often physical therapy is necessary to properly rehabilitate the tendon and gait to treat and prevent recurrence. Patients with significant pain may require immobilization with a pneumatic walker and crutches/walker in order to prevent further inflammation to the accessory bone and tendon. Patients that fail to respond to conservative treatment and prevention of recurrence may need surgical intervention. Patients with a flatfoot condition need further evaluation to reduce the overpull onto the posterior tibialis tendon and navicular bone.
