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Head of distal phalanx

The head of the distal phalanx is the rounded distal extremity of the distal phalanx in each finger. It supports the finger pad, forms the bony base underlying the nail bed, and provides attachment for fibrous septa of the pulp. This region contributes to fine touch, pinch force, and stability of the fingertip during manipulation.

It is composed of a dense cortical shell with a core of fatty cancellous bone and is the termination site for several soft-tissue structures that give the fingertip its sensitivity and mechanical strength.

Synonyms

  • Digital tuft

  • Terminal phalangeal head

  • Distal phalanx apex

Location and Structure

  • Situated at the distal end of the distal phalanx of each finger.

  • Shape: Expanded, bulbous terminal segment with a rounded contour.

  • Surfaces:

    • Dorsal: Supports the nail bed.

    • Palmar: Covered by thick skin, fibrous septa, and adipose tissue forming the finger pad.

    • Edges: Smoothly curved, continuous with the shaft proximally.

  • Composition: Thick cortical bone surrounding fatty cancellous marrow.

Relations

  • Dorsally: Nail plate and nail bed.

  • Palmar surface: Fibrous pulp, digital fat pads, and sensory receptors.

  • Laterally: Digital fibrous sheath and collateral ligament structures proximally.

  • Proximally: Shaft of distal phalanx and distal interphalangeal (DIP) joint.

  • Distally: Subcutaneous pulp and distal fingertip skin.

Attachments

  • Fibrous septa: Anchor the pulp tissue to the tuberosity and cortex of the phalanx.

  • Nail bed: Adheres firmly to dorsal surface, supported by the curvature of the bone.

  • Terminal extensor expansion: Inserts dorsally near the base of the distal phalanx (not directly on the head).

Function

  • Provides rigid support for the fingertip during fine manipulation.

  • Maintains structural integrity for gripping and precision tasks.

  • Supports the nail apparatus, aiding in tactile sensitivity.

  • Distributes pressure during fingertip contact and grasping.

Clinical Significance

  • Common involvement in tuft fractures from crush mechanisms.

  • Critical structure in nail-bed injuries and fingertip trauma.

  • Important in evaluation of suspected osteomyelitis, foreign bodies, and chronic fingertip pain.

  • Used as a landmark in hand surgery and reconstructive flap planning.

MRI Appearance

T1-weighted images:

  • Cortex: low signal (dark)

  • Marrow: bright signal due to fatty content

  • Nail bed: thin, intermediate signal layer dorsal to bone

  • Pulp: intermediate-to-bright soft tissue depending on fat composition

T2-weighted images:

  • Cortex: low signal

  • Marrow: bright, slightly less intense than T1 but still high

  • Soft tissues: intermediate-to-bright signal differentiating fat, fibrous septa, and skin

  • Nail bed and plate: intermediate signal

STIR:

  • Cortex: low signal

  • Marrow: intermediate-to-dark

  • Pulp fat: mostly suppressed (dark), fibrous septa remain visible as fine structures

  • Provides clear distinction between fat, bone, and fibrous tissue layers

CT Appearance

Non-Contrast CT:

  • Cortex: sharply defined high-attenuation bone

  • Marrow cavity: low-density region with fatty composition

  • Nail bed: thin soft tissue dorsal to bone

  • Excellent for identifying cortical detail and subtle fractures

MRI images

Head of distal phalanx HAND MRI CORONAL image-img-00000-00000

X Ray image

Head of distal phalanx bone