Accessory Ossicle Navicular Pain

Overview
For most people with an accessory navicular, the extra bone does not cause any problems and most are unaware of its presence. But certain activities or circumstances may cause the extra bone or the tibialis posterior tendon that contains it to grow irritated. This is called accessory navicular syndrome, and its possible causes include sprains, overuse, or wearing shoes that constantly rub against the bone. Individuals who have a collapsed arch (commonly known as flat feet) may be at greater risk of accessory navicular syndrome, assuming they have the extra bone, because of the added daily trauma placed on the tibialis posterior tendon.



Causes
This painful foot condition is caused by an extra bone in the foot called the accessory navicular. Only about 10% of people have this bone (4 to 21%), and not all of them will develop any symptoms. The navicular bone is one of the normal tarsal bones of the foot. It is located on the inside of the foot, at the arch.

Symptoms
The primary reason an accessory navicular becomes a problem is pain. There is no need to do anything with an accessory navicular that is not causing pain. The pain is usually at the instep area and can be pinpointed over the small bump in the instep. Walking can be painful when the problem is aggravated. As stated earlier, the condition is more common in girls. The problem commonly becomes symptomatic in the teenage years.

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
Excess weight will increase the force on the posterior tibial tendon as it inserts into the accessory navicular and will tend to precipitate or aggravate symptoms. If a patient with a symptomatic accessory navicular is overweight, then losing weight can be very helpful. Even losing 5-10lbs will decrease the amount of force going through the foot with each step by as much as 15-30lbs. This is because the foot acts like a lever serving to magnify the force absorbed by the foot with each step.



Surgical Treatment
If all nonsurgical measures fail and the fragment continues to be painful, surgery may be recommended. The most common procedure used to treat the symptomatic accessory navicular is the Kidner procedure. A small incision is made in the instep of the foot over the accessory navicular. The accessory navicular is then detached from the posterior tibial tendon and removed from the foot. The posterior tibial tendon is reattached to the remaining normal navicular. Following the procedure, the skin incision is closed with stitches, and a bulky bandage and splint are applied to the foot and ankle. You may need to use crutches for several days after surgery. Your stitches will be removed in 10 to 14 days (unless they are the absorbable type, which will not need to be taken out). You should be safe to be released to full activity in about six weeks.