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Head of proximal phalanx of great toe

The head of the proximal phalanx of the great toe (hallux) is the rounded distal articular portion of the proximal phalanx that forms the proximal component of the interphalangeal (IP) joint of the hallux. It plays an essential role in toe flexion and extension and in load transmission during gait.

It is an important landmark in foot anatomy, orthopedic assessment, and imaging of forefoot pathology.

Synonyms

  • Head of proximal phalanx of hallux

  • Distal articular head of proximal phalanx (great toe)

Location

  • Situated at the distal end of the proximal phalanx of the great toe

  • Proximal to the distal phalanx

  • Distal to the shaft of the proximal phalanx

  • Forms the proximal articular surface of the hallux interphalangeal joint

  • Located in the medial forefoot

Anatomical components

  • Rounded articular surface

  • Covered by hyaline cartilage

  • Subchondral bone beneath the cartilage

  • Capsular and ligamentous attachment zone:

    • Medial and lateral collateral ligaments

    • Joint capsule

  • Relationship to tendons:

    • Flexor hallucis longus (plantar)

    • Extensor hallucis longus (dorsal)

Relations

Anteriorly (dorsally):

  • Extensor hallucis longus tendon

  • Dorsal joint capsule

Posteriorly (plantarly):

  • Flexor hallucis longus tendon

  • Plantar plate

Medially:

  • Medial collateral ligament of the hallux IP joint

Laterally:

  • Lateral collateral ligament of the hallux IP joint

Distally:

  • Base of the distal phalanx

Proximally:

  • Shaft of the proximal phalanx

X-ray appearance

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

  • Head: Rounded distal contour of the proximal phalanx

  • Cortical outline: Smooth and continuous

  • Joint space: Clearly visible at the interphalangeal joint

  • Alignment: Centered articulation with the distal phalanx

CT appearance

Non-contrast CT:

  • Head: Well-defined rounded osseous structure

  • Cortical margins: Sharp and intact

  • Subchondral bone: Homogeneous trabecular pattern

  • Articular surface: Smooth contour

  • Relationship to distal phalanx: Clearly demonstrated

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Marrow of proximal phalanx: High signal intensity

  • Articular head: Clearly delineated against joint space

T2-weighted images:

  • Cortex: Low signal

  • Joint fluid: High signal outlining the articular surface

  • Articular cartilage: Intermediate signal

STIR:

  • Marrow fat suppression: Uniform

  • Head margins: Well visualized

  • Joint recesses: Bright signal

Proton density fat-saturated (PD FS):

  • Bone marrow: Suppressed fat signal

  • Joint fluid: High signal

  • Cartilage and ligaments: Well visualized with high contrast

MRI image

Head of proximal phalanx of great toe mri anatomy labelled image-img-00000-00000

CT image

Head of proximal phalanx of great toe ct

CT VRT 3D image

Head of proximal phalanx of great toe