Is Accessory Navicular Syndrome Dangerous

Overview
When there is injury to the muscle, fibrous tissue, or soft tissue of the navicular and the accessory navicular bones, symptoms will arise. This injury allows excessive movement between the bones. Fibrous tissue, ligaments and tendons have poor blood supply and are prone to poor healing. Often, this extra navicular bone lies near or attaches to the posterior tibial tendon. (See figure.) When the posterior tibial muscle contracts with movements such as foot inversion or plantar flexion, the posterior tendon moves and the accessory navicular bone moves. This can cause severe pain in those with Accessory Navicular Syndrome. It can become disabling to patients because the posterior tibial tendon attached to the navicular bone is responsible for supporting the medial arch during standing, walking and running. Activities which most of us do daily!



Causes
Just having an accessory navicular bone is not necessarily a bad thing. Not all people with these accessory bones have symptoms. Symptoms arise when the accessory navicular is overly large or when an injury disrupts the fibrous tissue between the navicular and the accessory navicular. A very large accessory navicular can cause a bump on the instep that rubs on your shoe causing pain.

Symptoms
One obvious problem with the accessory navicular is that it may be large and stick out from the inside of the foot. This can cause it to rub against shoes and so become quite painful. The fibrous connection between the accessory navicular and the navicualar, as well, is easy to injure, also leading to pain. This is kind of like a fracture, and such injuries cause the bone to move around too easily, leading to pain with activity. When the connection between the bones is injured in this way, the two bones do not always heal properly, so pain may continue unabated.

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
The foot may be placed in a cast or removable walking boot to allow the affected area to rest and decrease the inflammation. Physical therapy including exercises and treatments to strengthen the muscles, decrease inflammation, and prevent recurrence of the symptoms. Custom orthopedic devices that fit into the shoe providing arch support. Even after successful treatment, symptoms may reappear.



Surgical Treatment
The original procedure advocated by Kidner involved shelling out of the accessory navicular bone from within the insertional area of the posterior tibial tendon and rerouting this tendon under the navicular bone in hopes of restoring a normal pull of this tendon. When treating younger children, history has shown us that simply shelling out of the accessory navicular bone from within the tendon and remodeling the tuberosity of the navicular bone can give you satisfactory results.
In general, you want to reserve advancement of the posterior tibial tendon for adults or those who have a more significant flatfoot deformity. You may also use this approach after determining that quality custom orthotics are only resulting in a slight decrease of symptoms.