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What is an accessory navicular bone?

The accessory navicular is an extra bone or piece of cartilage material within the arch of the foot that might or might not produce problems. It is usually called an os navicularum or os tibiale externum. It is integrated inside the tendon of the posterior tibial muscle that inserts in the region. The extra bone is on the medial side of the navicular bone which is the bone which is at the top of the arch of the foot. It is present in from 5-15% of the population. It's not always a problem, however the prominence of the accessory bone might make pressure from the shoes painful. Occasionally the bone is in such a location that it does impact the angle of pull of the posterior tibial muscle which generally affect foot function and will cause several alignment problems, like a flat foot.

The diagnosis is generally by x-ray in which the presence of the extra bone is obvious. There are several types which the x-ray will help establish which one it is. The Geist classification divides the accessory navicular bones in to three different kinds. Each of the 3 kinds influences the structure and biomechanics of the feet in a different way and each of the 3 different types needs a unique treatment approach.

The goal of treatment solutions are to alleviate the symptoms preventing it getting painful. If the pain is particularly bad, then putting the foot within a cast or removable walking brace allows the affected region to rest and help the pain. Ice can also be used to relieve inflammation. Oral nonsteroidal anti-inflammatory drugs (NSAIDs) can be employed in combination with immobilization to further lessen the inflammation and pain. Physical exercises and therapies to strengthen the muscles can also be encouraged, in particular in the long run to help avert a recurrence of the symptoms. Foot orthotic inserts tend to be also very helpful to safeguard the area and be mainly beneficial in the event the accessory navicular is bringing about a flat foot.

The accessory navicular bone may be a particular concern is sports including skiing and ice skating. This is because the boots in these sports will go around the foot and it is rather firm. Consequently, if anyone has a acessory area of bone on the feet, just like an accessory navicular, this can be quite painful as well as challenging to treat. Things like doughnut type pads to get the force coming from the boot away from the spot is oftentimes helpful. This can be where the experience of a boot maker or a competent ski boot fitter is important. These experts are used to coping with these types of situations and can modify the footwear around the acessory navicular so it will be more comfortable. A podiatric doctor can frequently assist with all of this.

If the conservative nonsurgical therapies do not alleviate the symptoms, then surgical procedures can be appropriate. Surgical treatment can include taking out the additional bone, reshaping the area and reconstructing the posterior tibial tendon for increasing its biomechanics. This extra bone will not be required for normal foot function, and so theoretically it will not be a problem.