Podiatry Experts

The Accessory Navicular Bone

The accessory navicular is an extra piece of bone on the medial side of the foot pretty much on top of the mid-foot ( arch ) nearby its top point. The bone is integrated inside the posterior tibial tendon which attaches into the navicular bone towards the top of the mid-foot ( arch ). The extra bone may also be referred to as the os navicularum or os tibiale externum. This is genetic, so is existing since birth. There are several different kinds of accessory navicular and the Geist typology is most typically used. This categorization separates the accessory navicular into three variations:

Type 1 accessory navicular bone:
This is the textbook ‘os tibiale externum’ making up to 30% of the occurrences; it's a 2-3mm sesamoid bone embedded inside the distal portion of the tendon with no connection to the navicular tuberosity and may even be divided from the bone by up to 5mm

Type 2 accessory navicular bone:
This variety makes up 55% of the accessory navicular bones; it is triangular or heart-shaped and connected to the navicular bone through cartilage. It might ultimately merge to the navicular to make one bone.

Type 3 accessory navicular bone:
Pronounced navicular tuberosity. It might have been a Type 2 that has merged to the navicular

The common clinical feature associated with the accessory navicular is the prominence on the inside aspect of the mid-foot ( arch ). Due to the extra bone there, this has an effect on how well the mid-foot ( arch ) muscles perform and may cause a flat foot. Inflexible type shoes, like ski boots, may also be quite uncomfortable to use because of the enlarged pronounced bone.

The treatment is directed at the symptoms. When the flatfoot is an issue, then ice, immobilisation and also pain relief drugs may be required to start with. After that, physical rehabilitation and foot orthotic devices to support the foot are used. When the pain is caused by force from the style of footwear that ought to be used, then donut type padding is required to get force off the painful region or the shoes may need to be adjusted.

If these non-surgical treatment options are not able to minimize the symptoms of the accessory navicular or the problem is an ongoing one, then surgery may be an appropriate alternative. This requires removing the accessory bone and restoring the insertion of the posterior tendon so its function is improved upon.