Radiological study of Os Navicular and its Anatomical variants

Abstract

Introduction: Accessory ossicles are the skeletal variations of the ankle and foot that can cause painful syndromes. Accessory navicular bone also known as Os Naviculare secundarium, Os tibiale externum, is one of the most common accessory ossicle of the foot with an incidence of 4–21%. The presence of an OSN can trigger various foot problems such as tibialis posterior tendon pathology, flattening of the medial longitudinal arch and medial foot pain. Aim: To study the incidence, anatomical variants and distribution of Os Navicular (OSN). Materials and Methods: Accessory navicular bones were retrospectively examined in 1,000 (589 men and 411 women) radiographs of foot in the age group 12-80 years. Anterior-posterior/oblique X-ray images were observed for the presence, anatomical variant, and morphology of OSN. All the data was recorded and analysed. Results: Out of 1000 radiographs of the foot, 144 cases of OSN were observed with varying shape and size which accounts for 14.4% incidence. All three types of OSN were noted in the present study with Type II being the most predominant variant with incidence of 50%, while Type I with an incidence of 34.72% and Type III with an incidence of 15.27%. Conclusion: Knowledge regarding the anatomical variants of OSN is important for surgeons and radiologists in the interpretation of foot radiographs and management of cases presenting with foot Pain.

Keywords

• medial foot pain
• medial longitudinal arch
• os tibiale externum
• tibialis posterior tendon pathology