Foot Pain Accessory Navicular Bone

Overview
In an ideal situation, the navicular bone and the accessory bone will fuse together to form one bone. The problem that occurs is that sometimes the two bones do not fuse together and the patient is left with what is known as a fibrous union or basically a non solid union of bone to bone. This fibrous union is more like scar tissue and in theory can cause pain when excessive strain is placed upon it.



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
A visible bony lump on the inner part of the foot, towards the middle, just above the arch of the foot. Redness, swelling, and sensitivity of the bony prominence. Pain or throbbing in the middle of the foot and the arch. Difficulty with foot movement and activity. Possible skin callous or skin irritation caused by footwear rubbing over the lump. Not everyone who has an accessory navicular will develop these problems. When problems do occur, they may begin in early adolescence. The obvious indication is a painful bump on the inside of the foot, which hurts to touch, and causes problems that gradually become worse, and which are aggravated by activity, walking, etc., leading to all the problems discussed here. Pain may be worse towards the end of the day, and continue into the night.

Diagnosis
Keep in mind there are two different types of accessory navicular bones, which you can distinguish by getting a weightbearing AP X-ray of the foot. Dwight has classified type I as a small, round and discreet accessory bone just proximal to the main navicular bone. Geist described the type II accessory bone, which is closely related to the body of the navicular but separated by an irregular plate of dense fibro-cartilage.

Non Surgical Treatment
The goal of non-surgical treatment for accessory navicular syndrome is to relieve the symptoms. The following may be used. Immobilization. Placing the foot in a cast or removable walking boot allows the affected area to rest and decreases the inflammation. Ice. To reduce swelling, a bag of ice covered with a thin towel is applied to the affected area. Do not put ice directly on the skin. Medications. Oral nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be prescribed. In some cases, oral or injected steroid medications may be used in combination with immobilization to reduce pain and inflammation. Physical therapy. Physical therapy may be prescribed, including exercises and treatments to strengthen the muscles and decrease inflammation. The exercises may also help prevent recurrence of the symptoms. Orthotic devices. Custom orthotic devices that fit into the shoe provide support for the arch, and may play a role in preventing future symptoms. Even after successful treatment, the symptoms of accessory navicular syndrome sometimes reappear. When this happens, non-surgical approaches are usually repeated.



Surgical Treatment
Fusion of the accessory navicular to the navicular with screws is required when there is a large accessory navicular bone and removal of this bone would reduce the articular surface of the Navicular to the talus (coxa pedis). Fusion will relieve pain without disrupting the tibialis posterior tendon insertion nor narrowing talar head support. In most instances, a patient’s recovery will be as follows. 0-6 weeks: Immobilization (in case or cast boot) non-weight-bearing or touch weight-bearing. 6-10 weeks: Increasing activity in a cast boot. Physical therapy to work on strength and balance. Full recovery after 9 weeks-2 months. In some patients (where the posterior tibial tendon is still intact and functioning) the treating surgeon may allow weight-bearing as tolerated in a cast boot immediately after surgery.