What Is Accessory Navicular Syndrome

Overview
An accessory navicular bone is an accessory bone of the foot that occasionally develops abnormally causing a plantar medial enlargement of the navicular. The accssory navicular bone presents as a sesamoid in the posterior tibial tendon, in articulation with the navicular or as an enlargment of the navicular. Navicular (boat shaped) is an intermediate tarsal bone on the medial side of the foot. It is located on the medial side of the foot, and articulates proximally with the talus. Distally it articulates with the three cuneiform bones. In some cases it articulates laterally with the cuboid. The tibialis posterior inserts to the os naviculare. The tibialis posterior muscle also contracts to produce inversion of the foot and assists in the plantar flexion of the foot at the ankle. Tibialis posterior also has a major role in supporting the medial arch of the foot. This supports is compromised by abnormal insertion of the tendon into the accessory navicular bone when present. This lead to loss of suspension of tibialis posterior tendon and may cause peroneal spastic pes planus or simple pes planus. But, yet a cause and effect relationship between the accessory navicular and pes planus is doubtful and is yet unproved clearly.



Causes
It is commonly believed that the posterior tibial tendon loses its vector of pull to heighten the arch. As the posterior muscle contracts, the tendon is no longer pulling straight up on the navicular but must course around the prominence of bone and first pull medially before pulling upward. In addition, the enlarged bones may irritate and damage the insertional area of the posterior tibial tendon, making it less functional. Therefore, the presence of the accessory navicular bone does contribute to posterior tibial dysfunction.

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
A combination of the following non-surgical treatments may be used to relieve the symptoms of accessory navicular syndrome. Immobilizing the foot with a cast or a removable walking boot allows the foot to rest and reduces inflammation. Applying ice to the affected area is an effective way to reduce swelling and inflammation. Wrap a bag of ice with a thin towel and apply for intervals of 15 to 20 minutes. Never put ice directly on the skin. Oral nonsteroidal anti-inflammatory drugs (NSAIDs) including aspirin or ibuprofen might be prescribed. Sometimes, a combination of immobilization and oral or injected corticosteroid medications may reduce pain and inflammation. Physical therapy may be prescribed to include exercises and treatments that increase muscle strength, decrease inflammation and help prevent the recurrence of symptoms. Custom orthotic devices worn in the shoe provide arch support and may prevent future symptoms from developing. The symptoms of this syndrome may reappear even after successful treatment. If so, non-surgical treatments are often repeated.



Surgical Treatment
Surgical treatment of the accessory navicular syndrome with simple excision has the advantages of less invasive to the posterior tibial tenden and the medial longitudinal arch of the foot, shorter time of immobilization of the foot and stay in hospital, small incision and good clinical results. This procedure is one of the best selective treatments for the accessory navicular syndrome, especially for the patients without flatfoot deformity and old sprain injury.