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Head of middle phalanx

The head of the middle phalanx is the distal expanded end of the middle phalanx of the fingers (digits II–V). It forms the proximal articular component of the distal interphalangeal (DIP) joint and plays a key role in finger motion by allowing smooth articulation with the base of the distal phalanx.

It is an important anatomical landmark in hand anatomy, trauma evaluation, arthritic assessment, and small joint imaging.

Synonyms

  • Distal head of the middle phalanx

  • Condyles of the middle phalanx

Location

  • Situated at the distal end of the middle phalanx

  • Between the shaft of the middle phalanx proximally and the distal phalanx distally

  • Forms the proximal articular surface of the DIP joint

  • Present in digits II to V

  • Absent in the thumb (which has only two phalanges)

Anatomical components

  • Bicondylar articular surface:

    • Medial and lateral condyles

  • Central groove:

    • Separates the condyles and guides joint motion

  • Articular cartilage covering:

    • Smooth hyaline cartilage

  • Subchondral bone:

    • Supports joint surface

Relations

Anteriorly (volar):

  • Flexor digitorum profundus tendon insertion distal to the head

  • Volar plate of the DIP joint

Posteriorly (dorsal):

  • Terminal extensor tendon insertion distal to the head

Medially and laterally:

  • Collateral ligaments of the DIP joint

Distally:

  • Base of the distal phalanx

Proximally:

  • Neck of the middle phalanx

X-ray appearance

Plain radiographs (PA, oblique, lateral finger views):

  • Head: Seen as a rounded or bicondylar distal end of the middle phalanx

  • Articular margins: Smooth and symmetric

  • Joint relationship: Clearly forming the proximal surface of the DIP joint

  • Cortical outline: Sharp and continuous

CT appearance

Non-contrast CT:

  • Head: Well-defined distal expansion of the middle phalanx

  • Cortical margins: Smooth and sharply outlined

  • Trabecular pattern: Normal cancellous bone within the condyles

  • Articular surface: Accurately visualized curvature and congruity

  • Utility: Excellent for detailed bony contour assessment

MRI appearance

T1-weighted images:

  • Cortical bone: Low signal intensity

  • Marrow within the head: High signal intensity

  • Articular surface: Clearly delineated

T2-weighted images:

  • Cortex: Low signal

  • Joint fluid: High signal outlining the articular surface

  • Articular cartilage: Intermediate-to-high signal

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Subchondral bone and joint margins: Well visualized

  • Joint recesses: Bright signal

Proton density fat-saturated (PD FS):

  • Bone marrow: Fat-suppressed signal

  • Cartilage: Intermediate signal

  • Joint fluid: High signal

  • Collateral ligaments: Seen as low-signal bands flanking the head

MRI image

Head of middle phalanx mri image

X-Ray image

Head of middle phalanx x ray