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Interphalangeal sesamoid of great toe

The interphalangeal sesamoid of the great toe is a small accessory bone or cartilaginous nodule located within the plantar aspect of the interphalangeal (IP) joint of the hallux. It is embedded in the plantar plate or tendon complex and plays a role in modifying pressure distribution and tendon mechanics at the distal great toe.

It represents a normal anatomical variant that is frequently encountered in imaging and should be distinguished from fractures or pathological ossifications.

Synonyms

  • Hallux interphalangeal sesamoid

  • IP joint sesamoid of the great toe

Location

  • Situated on the plantar aspect of the interphalangeal joint of the great toe

  • Between the proximal and distal phalanges of the hallux

  • Embedded within the plantar plate or flexor hallucis longus tendon fibers

  • Inferior to the articular surfaces of the IP joint

  • Deep to the plantar skin and subcutaneous tissues

Anatomical components

  • Small sesamoid bone or fibrocartilaginous nodule

  • Usually oval or round in shape

  • May be ossified or cartilaginous depending on age and individual variation

  • Surrounded by fibrous tissue and joint capsule

  • Often single, occasionally bipartite

Relations

Superiorly:

  • Articular surfaces of the proximal and distal phalanges

Inferiorly:

  • Plantar skin and subcutaneous fat

Anteriorly:

  • Distal phalanx of the hallux

Posteriorly:

  • Proximal phalanx of the hallux

Medially and laterally:

  • Plantar plate and joint capsule

X-ray appearance

Plain radiographs (AP, lateral, oblique foot views):

  • Sesamoid: Small, well-corticated ossicle beneath the IP joint

  • Shape: Round or oval

  • Position: Plantar to the IP joint line

  • May be absent or radiolucent if cartilaginous

CT appearance

Non-contrast CT:

  • Sesamoid: Well-defined, corticated ossicle at the plantar IP joint

  • Density: Similar to cancellous bone with cortical margins

  • Morphology: Clearly demonstrates size, shape, and multipartite variants

  • Relationship: Precisely localized relative to phalanges and joint space

MRI appearance

T1-weighted images:

  • Ossified sesamoid: High signal marrow with low-signal cortical rim

  • Cartilaginous sesamoid: Intermediate-to-low signal

  • Surrounding fat: High signal providing contrast

T2-weighted images:

  • Bone marrow: Intermediate signal

  • Cartilage or fibrocartilage: Intermediate-to-high signal

  • Joint fluid: High signal outlining the sesamoid

STIR:

  • Fat suppression: Suppresses marrow fat signal

  • Sesamoid margins: Clearly visualized against suppressed background

  • Plantar plate and capsule: Well delineated

Proton density fat-saturated (PD FS):

  • Sesamoid: Low-signal cortical rim with suppressed marrow fat

  • Joint fluid: High signal

MRI image

Interphalangeal sesamoid of great toe mri anatomy labelled image-img-00000-00000

MRI image

Interphalangeal sesamoid of great toe mri anatomy labelled image-img-00000-00000_00001

CT image

Interphalangeal sesamoid of great toe ct

X Ray image

Interphalangeal sesamoid of great toe