Accessory Ossicle Navicular Pain

Overview
Accessory navicular syndrome occurs when a type II accessory navicular (or "os tibiale externum") becomes painful due to movement across the pseudojoint between the ossicle and the navicular bone. The syndrome presents on MRI with bone marrow oedema signal (hypointense T1, hyperintense T2/STIR) in both the accessory ossicle and navicular. It can be inferred on musculoskeletal ultrasound if a patient's pain is located at a type II accessory navicular and the patient is tender to transducer pressure. Ultrasound can also be useful to compare with the contralateral side.



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
What are the signs/symptoms of Accessory Navicular Syndrome? Pain in the foot following trauma (such as after an ankle sprain) Chronic irritation from shoes or other footwear rubbing against the bone. A visible bony prominence on the inner side of the foot just above the arch. Redness and swelling of that area. Vague pain or throbbing in the arch mostly occuring during or after periods of physical activity. Symptoms appear most often during adolescence, but some may not occur until adulthood.

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
Treating accessory navicular syndrome is focused on relieving symptoms. Some treatment methods are Icing to reduce swelling. Immobilization with a cast or walking boot to reduce inflammation and promote healing. Medications to reduce pain and inflammation. Physical therapy to strengthen muscles. Orthotics to support the arch. Surgery may be needed to remove the accessory bone and reshape the area if other methods are not successful.



Surgical Treatment
The above non-surgical options should be enough to treat accessory navicular syndrome. If they fail, a surgery would be necessary to remove the extra bone that has been causing the problems. The most common procedure for this condition is known as the Kidner procedure where a small incision is made over the navicular bone. The accessory navicular is identified and dissected free from the posterior tibial tendon. The posterior tibial tendon is then reattached to the remaining navicular bone.