Type Ii Accessory Navicular Bone

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.



Causes
An injury to the fibrous tissue connecting the two bones can cause something similar to a fracture. The injury allows movement to occur between the navicular and the accessory bone and is thought to be the cause of pain. The fibrous tissue is prone to poor healing and may continue to cause pain. Because the posterior tibial tendon attaches to the accessory navicular, it constantly pulls on the bone, creating even more motion between the fragments with each step.

Symptoms
This painful condition is called accessory navicular syndrome. Accessory navicular syndrome (ANS) can cause significant pain in the mid-foot and arch, especially with activity. Redness and swelling may develop over this bony prominence, as well as extreme sensitivity to pressure. Sometimes people may be unable to wear shoes because the area is too sensitive.

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
Ideally, getting rid of the symptoms of accessory navicular syndrome will involve soothing the inflammation and irritation in your foot. So, for starters, your podiatrist may have you rest the area, allowing the inflamed tendon and bone to heal. This may be accomplished by wearing a cast or boot designed to keep you from moving the problem area. Your podiatrist may also suggest using ice to reduce the swelling and inflammation, and anti-inflammatory medications (like ibuprofen, or sometimes a cortisone shot or other steroid medication).



Surgical Treatment
After the anesthesia is administered you will be heavily sedated and placed on your stomach. Surgeons will place a tourniquet around your thigh and an incision will be made on the inside of the foot. The posterior tibial tendon will be moved as necessary and the accessory navicular will be removed. Surgeons will repair the posterior tibial tendon with sutures or suture anchors, and the wound will be closed. A splint will be placed on the foot for stabilization and immobilization. You will be permitted to leave the surgical center once you have been cleared by the anesthesiologist. Plan ahead to have a friend or family member take your prescription to a pharmacy to pick up your post-op medication. Use narcotic pain medications before bed or if numbness in your foot begins to dull. Schedule a post-op visit for 4 weeks after the procedure.