Recovery From Accessory Navicular Bone Removal

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
Adolescence is a common time for the symptoms to first appear. This is a time when bones are maturing and cartilage is developing into bone. Sometimes, however, the symptoms do not occur until adulthood. The signs and symptoms of accessory navicular syndrome include a visible bony prominence on the midfoot (the inner side of the foot, just above the arch) Redness and swelling of the bony prominence. Vague pain or throbbing in the midfoot and arch, usually occurring during or after periods of activity.

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
Initial treatment is conservative. With the first episode of symptoms, a medial heel wedge, anti-inflammatories, and physical therapy can be helpful. If very painful, a cast or boot may be needed for a short period time before the wedge and physical therapy can be initiated. Very rarely is a steroid injection warranted or recommended. As the pain improves, patients can resume activities. For a minority of patients, an arch support or custom orthotic can help to take some of the extra pressure off of the accessory navicular and the posterior tibial tendon.



Surgical Treatment
For patients who have failed conservative care or who have had recurrent symptoms, surgery can be considered. Surgical intervention requires an excision of the accessory navicular and reattachment of the posterior tibial tendon to the navicular. Often times, this is the only procedure necessary. However, if there are other deformities such as a flat foot or forefoot that is abducted, other procedures may be required.