Incidence
1 - 2 %
Anatomy
Medial Aspect of foot
- proximal to navicular
- part of T posterior tendon
Usually will fuse with navicular (50%)
Issues
1. Probably not a cause of flat foot
- excising accessory navicular / rerouting / reattaching tibialis posterior
- will not help pes planus
2. Pain
- may fracture
- may cause insertional tendonitis
Classification
Type 1
Small ossicle proximal to insertion
Type 2
Synchondrosis
- may fracture with injury
Management
- treat in cast 6/52
- excise if symptomatic
Type 3
Large cornuate navicular
- likely that the accessory has fused
Bone Scan
Identifies if accessory navicular cause of symptoms
MRI
Show oedema about a symptomatic accessory navicular
DDx
T Posterior tendonitis
Navicular stress fracture
Management
Non operative
Rest
Moon Boot
Operative
Kidner Procedure
- medial incision dorsally over navicular
- enucleate accessory navicular from tendon
- may need to take away navicular prominence
- reattach tendon if necessary through drill holes