Accessory Bones

Accessory navicular

• Incidence

Present in 10% of children

More common in girls than boys

• Pathology

Congenital abnormality when navicular tuberosity develops from a secondary centre of ossification

Two types-

1: small accessory bone without attacment to navicular, sesamoid in post tib tendon (os tibiale externum)

2: definite part of the navicular

• History

Usually develop symptoms after 5 yrs of age- localised medial foot pain, often precipitated by trauma, rubbing of shoes over prominence

• Examination

Prominent medial aspect of navicular, normal range of movement of foot joints

• Investigation

AP or oblique Xray