The symptomatic accessory tarsal navicular bone: assessment with MR imaging.

Abstract

To determine if a symptomatic accessory navicular bone, a normal variant, displays a pattern of altered signal intensity on magnetic resonance (MR) images indicative of an abnormality that could account for the patient's foot pain. Both feet were imaged in seven patients with an accessory navicular bone on radiographs and unilateral foot pain. Five patients had focal medial foot pain, and two had vague, diffuse pain. T1-weighted spin-echo and T2-weighted fat-suppressed sequences were used. A bone marrow edema pattern (BMEP) was noted in the accessory navicular bones of the five patients with focal pain and in the adjacent navicular tuberosities of three of them. The two patients with vague pain showed no osseous or soft-tissue abnormalities. Two patients with positive MR images underwent surgical excision of the accessory navicular bone, and histologic examination revealed osteonecrosis in one patient. The BMEP in a symptomatic accessory navicular bone is indicative of chronic stress and/or osteonecrosis. This information can furnish an objective basis for surgical or conservative management.