The accessory navicular is common anatomic variant - tuberosity of navicular develops from secondary ossification center
First described by Bauhin in 16051 and later by Pfitzner in 18362
Synonyms: os navicularis, accessory schapoid (in early literature), os naviculare secundarium, prehallux, os tibiale externum, hooked naviuclar, bifurcate navicular
Prevalence of 4-14%
Commonly associated with a pronated/flat foot and posterior tibial dysfunction.
Obvious on x-ray; remains prominent on movement of subtalar joint (talar head prominence will disappear on STJ supination); may present with pain from shoe pressure or pain from posterior tibial tendonitis.
Type 1 – independent of navicular and is considered a sesamoid in posterior tibial tendon – well-defined oval shape. 2-5mm in diameter and about 3-7mm posteromedial to navicular – not usually symptomatic
Type 2 – united to navicular by cartilaginous bar – secondary ossification centre – usually 9-12mm and situated 1-2mm from posteromedial aspect of navicular tuberosity
Type 3 – enlarged posteromedial tuberosity – possibly due to fusion of type 2
Surgical – removal of ossicle (Type 1); excision of prominence (Type 2 & 3); may result in weakness of posterior tibial tendon due to alteration in insertion of posterior tibial tendon, so surgical advancement of tendon is often used.
"The Geist classification divides these into three types:
type 1 accessory navicular bone
also known as os tibiale externum
2-3mm sesamoid bone embedded within the distal portion of the posterior tibial tendon
no cartilaginous connection to the naviculam tuberosity and may be separated from it by up to 5mm
accounts for 30% of accessory navicular bones
type 2 accessory navicular bone
triangular or heart-shaped
measures up to 12 mm
accounts for 50-60% of all ossicles
connected to the navicular tuberosity by a 1-2-mm thick layer of either fibrocartilage on hyaline cartilage
eventual osseous fusion to the navicular tuberosity may take place
type 3 accessory navicular bone
an especially prominent navicular tuberosity called a cornuate navicular
thought to represent a fused type 2 and is occasionally symptomatic as a result of painful bunion formation over the bony protuberance"
DWIGHT 1920 classification:
RSS Feed of Latest Publications on Accessory Navicular: