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Trochlea of phalanx of great toe

The trochlea of the phalanx of the great toe refers to the pulley-shaped articular surface located at the distal end of the proximal phalanx or at the distal end of the distal phalanx (depending on anatomical reference), forming part of the interphalangeal joint of the hallux. It facilitates smooth flexion and extension movements by providing a congruent articulating surface with the adjacent phalanx.

It is an important anatomical feature in foot biomechanics, gait, orthopedic evaluation, and imaging of the forefoot.

Synonyms

  • Hallux phalangeal trochlea

  • Trochlear surface of the great toe phalanx

Location

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

  • Forms part of the interphalangeal joint of the hallux

  • Between the proximal and distal phalanges of the great toe

  • Anterior to the plantar soft tissues

  • Posterior to the dorsal extensor apparatus

Anatomical components

  • Convex, pulley-shaped articular surface

  • Medial and lateral lips forming guiding ridges

  • Central groove allowing stable articulation

  • Covered by hyaline cartilage

  • Subchondral bone supporting the articular surface

Relations

Proximally:

  • Shaft of the proximal phalanx (or distal phalanx, depending on reference)

Distally:

  • Base of the adjacent phalanx

Plantar:

  • Flexor hallucis longus tendon and plantar plate

Dorsal:

  • Extensor hallucis longus tendon

Medially and laterally:

  • Collateral ligaments of the interphalangeal joint

X-ray appearance

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

  • Trochlea: Seen as a smooth, curved distal articular contour

  • Joint space: Clearly defined interphalangeal joint line

  • Margins: Well-corticated and symmetric

  • Alignment: Contributes to normal joint congruity

CT appearance

Non-contrast CT:

  • Trochlea: Well-defined convex articular surface

  • Subchondral bone: Uniform density

  • Cortical outline: Smooth and continuous

  • Joint congruency: Precisely demonstrated

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal

  • Marrow: High signal within the phalanx

  • Trochlear contour: Clearly delineated against surrounding soft tissues

T2-weighted images:

  • Articular cartilage: Intermediate-to-high signal

  • Joint fluid: High signal outlining the trochlear surface

  • Cortex: Low signal

STIR:

  • Marrow fat: Uniform suppression

  • Trochlea margins: Well visualized

  • Joint space: High signal from synovial fluid

Proton density fat-saturated (PD FS):

  • Cartilage and joint fluid: High signal contrast

  • Subchondral bone: Low signal

MRI image

Trochlea of phalanx of great toe mri anatomy labelled image-img-00000-00000

CT image

Trochlea of phalanx of great toe ct