Do I Have Accessory Navicular Syndrome

Overview
The accessory navicular (os navicularum or os tibiale externum) is an extra bone or piece of cartilage located on the inner side of the foot just above the arch. It is incorporated within the posterior tibial tendon, which attaches in this area. An accessory navicular is congenital (present at birth). It is not part of normal bone structure and therefore is not present in most people. People who have an accessory navicular often are unaware of the condition if it causes no problems. However, some people with this extra bone develop a painful condition known as accessory navicular syndrome when the bone and/or posterior tibial tendon are aggravated. Many people with accessory navicular syndrome also have flat feet (fallen arches). Having a flat foot puts more strain on the posterior tibial tendon, which can produce inflammation or irritation of the accessory navicular.



Causes
People who have an accessory navicular often are unaware of the condition if it causes no problems. However, some people with this extra bone develop a painful condition known as accessory navicular syndrome when the bone and/or posterior tibial tendon are aggravated. This can result from any of the following. Trauma, as in a foot or ankle sprain. Chronic irritation from shoes or other footwear rubbing against the extra bone. Excessive activity or overuse.

Symptoms
It?s common for any symptoms to present during adolescence, when bones are maturing, though problems may not occur until adulthood. You may notice a bony prominence on the inner side of the midfoot. There may or may not be redness and swelling around this bump, especially if it rubs against footwear. You may be prone to blisters or sores in the area. Pain generally involves a vague ache or throbbing in the midfoot and arch as well, especially when you?re active. Many people with this syndrome develop flat feet, too, which can create additional strain in the foot.

Diagnosis
To diagnose accessory navicular syndrome, medical staff ask about the patient?s activities and symptoms. They will examine the foot for irritation or swelling. Medical staff evaluate the bone structure, muscle, joint motion, and the patient?s gait. X-rays can usually confirm the diagnosis. MRI or other imaging tests may be used to determine any irritation or damage to soft-tissue structures such as tendons or ligaments. Because navicular accessory bone irritation can lead to bunions, heel spurs and plantar fasciitis, it?s important to seek treatment.

Non Surgical Treatment
Treatment of the accessory navicular begins with rest, which may include activity modification or temporary immobilization in a boot or a brace. Once the inflammation subsides the foot needs to be supported. The support consists of a specially designed orthotic arch support. Occasionally, the orthotic will dig into the edge of the accessory navicular bone under the arch of the foot. This is very uncomfortable. For this reason the orthotic support needs to be carefully made. The orthotic support will help control (but not cure) the flat foot and will often decrease the inflammation on the navicular.



Surgical Treatment
If non-operative treatment fails to relieve the patient’s symptoms, surgical intervention may be warranted. The standard operative treatment of an accessory navicular is a Kidner procedure. However, if surgery is undertaken it is important that it address the underlying source of the patients pain.