Os tibiale navicular refers to an extra bone found in the foot. An accessory bone is a bone that is not normally found in the average human, but in most cases is not considered abnormal. This condition represents a secondary ossification center (growth center) of the navicular bone. It is present from birth. The navicular bone Where is the Achilles heel
? found on the inside part of the foot.Causes
Like all painful conditions, ANS has a root cause. The cause could be the accessory navicular bone itself producing irritation from shoes or too much activity. Often, however, it is related to injury of one of the structures that attach to the navicular bone. Structures that attach to the navicular bone include abductor hallucis muscle, plantar calcaneonavicular ligament (spring ligament) parts of the deltoid ligament, posterior tibial tendon.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
Your doctor will diagnose an accessory navicular by examining your child?s foot. Your physician may also obtain x-rays to confirm the accessory navicular and to rule out other conditions.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
Once the navicular inflammation has lessened it is not necessary to perform surgery unless the foot becomes progressively flatter or continues to be painful. For these children, surgery can completely correct the problem by removing the accessory navicular bone and tightening up the posterior tibial tendon that attaches to the navicular bone. The strength of this tendon is integral to the success of this surgery as well as the arch of the foot. Following surgery the child is able to begin walking on the foot (in a cast) at approximately two weeks. The cast is worn for an additional four weeks. A small soft ankle support brace is then put into the shoe and worn with activities and exercise for a further two months.