Presentation
Ankle strain. Exact mechanism unknown, probable hyperpronation. Tenderness at ankle and over mid shaft of fibula.
Patient Data
No fracture or dislocation. Well-aligned articular surfaces and joint spaces. No joint effusion.
Incidental note is made of an os trigonum, located below the posterior part of the ankle joint, and of a supranavicular bone, partially incorporated by the navicular.
Zoom view of the hind- and proximal midfoot portions of the study better depicts the accessory ossicle in partial coalition with the navicular bone.
Case Discussion
Developmental ossicles or accessory bones may appear anywhere in the skeleton. They may appear separated or in fusion with the main bone. Being mostly asymptomatic, they are important to know for radiologists, as misinterpretation should be avoided. The supranavicular bone is no exception to this rule.
The well known work of reference by Theodore Keats et al ´Atlas of Normal Roentgen Variants that may simulate disease´ might at times be the most readily available book in any reading room (or the opposite due to very frequent usage by your colleagues).