Extra Bone In Foot Accessory Navicular

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
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
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
Patients with a painful accessory navicular may benefit with four to six physical therapy treatments. Your therapist may design a series of stretching exercises to try and ease tension on the posterior tibial tendon. A shoe insert, or orthotic, may be used to support the arch and protect the sore area. This approach may allow you to resume normal walking immediately, but you should probably cut back on more vigorous activities for several weeks to allow the inflammation and pain to subside. Treatments directed to the painful area help control pain and swelling. Examples include ultrasound, moist heat, and soft-tissue massage. Therapy sessions sometimes include iontophoresis, which uses a mild electrical current to push anti-inflammatory medicine to the sore area.



Surgical Treatment
The original procedure advocated by Kidner involved shelling out of the accessory navicular bone from within the insertional area of the posterior tibial tendon and rerouting this tendon under the navicular bone in hopes of restoring a normal pull of this tendon. When treating younger children, history has shown us that simply shelling out of the accessory navicular bone from within the tendon and remodeling the tuberosity of the navicular bone can give you satisfactory results.
In general, you want to reserve advancement of the posterior tibial tendon for adults or those who have a more significant flatfoot deformity. You may also use this approach after determining that quality custom orthotics are only resulting in a slight decrease of symptoms.