Accessory navicula




 

Accessory navicular

Os naviculare

3 types

Type I accessory navicular 

Small, round sesamoid

Separate from navicular

Within the substance of PT tendon

Rarely associated with symptoms


Accessory navicular

Os naviculare

3 types

Type II accessory navicular

Synchondrosis with the body of navicular

Disruption by traction or shear forces 

 → Symptom 

Accessory navicular

Os naviculare

3 types

Type III accessory navicular 

Absence of synchondrosis

Completely fusion with the navicular 

“Horn-shaped navicular”

Clinical Findings 

Asymptomatic become symptomatic 

After mild trauma

Causing disruption of synchondrosis


Progressively worsening medial midfoot pain

Exacerbated by sports activity or Shoe wear


Bump on the medial arch

Tenderness over the medial prominence




Radiographic evaluation

X-ray

Standing AP, Lateral, External oblique


Bone scan

Symptomatic patients

Signal intensity at the site of ossicle


MRI

Soft tissue anatomy

PT tendon insertion

Synchondrosis

Edema of bony structure  

Association with flat foot ?

FC Kidner (1929, JBJS)

Posterior tibial tendon

Support to the medial longitudinal arch

Compromised by 

Abnormal insertion to the accessory navicular

Resulted in flat foot 


Relationship between accessory navicular & flat foot 

Uncertatin



Treatment

Nonsymptomatic → Observation


Surgery

Indication

Symptomatic accessory navicular with point tenderness


Symptom relief around tuberosity 

Reducing fatigue from arch strain 


But, arch correction cannot be predictable



Treatment

Original Kidner procedure

Excision of accessory navicular

Advancement of PT tendon to the medial cuneiform


Modified Kidner procedure

Excision of accessory navicular

Side-to-side repair of PT tendon



Pearls

Avoid violating the T-N joint capsule


Resection of large type II or III ossicle

Nearly complete detachment of PT tendon

Reattachment to the residual navicular 


Concomitant correction of associated flatfoot deformity

Controversial 


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