Topics

Topic

design image
Distal phalanx of hand

The distal phalanx is the terminal bone of each digit in the hand, supporting the pulp of the fingertip and the nail bed. It provides the rigid framework necessary for fine tactile sensation, object manipulation, and precision grip.

Each distal phalanx consists of a broad base, tapered shaft, and expanded tuft at its distal end. The tuft supports the pulp pad and nail bed, while the base articulates with the head of the middle phalanx to form the distal interphalangeal (DIP) joint. The bone has a rich vascular supply and sensory innervation, making fingertip injuries particularly painful and prone to bleeding.

The thumb distal phalanx is larger, flatter, and stronger than those of the other fingers, reflecting its role in grasp and opposition.

Synonyms

  • Terminal phalanx

  • Ungual phalanx

  • Tuft phalanx

Location and Structure

  • The distal phalanx is located at the tip of each finger, distal to the middle phalanx (or proximal phalanx in the thumb).

  • Base: Proximal end that articulates with the head of the middle phalanx at the DIP joint.

  • Shaft: Tapered body connecting base and tuft, containing trabecular bone surrounded by a thin cortical shell.

  • Tuft: Expanded distal end supporting the pulp pad and nail bed, rich in vascular and sensory supply.

  • Surface anatomy: Dorsal surface supports the nail bed; volar surface provides attachment for the digital pulp and flexor tendon.

Relations

  • Dorsally: Nail bed, germinal matrix, and extensor tendon expansion

  • Ventrally (volar): Flexor digitorum profundus tendon and digital pulp tissue

  • Laterally: Digital neurovascular bundles (arteries and nerves)

  • Proximally: Distal interphalangeal joint and middle phalanx head

Attachments

  • Flexor digitorum profundus (FDP): Inserts into the volar base of the distal phalanx, flexing the DIP joint.

  • Extensor digitorum longus / indicis / digiti minimi: Attach dorsally, extending the DIP joint.

  • Fascial and ligamentous attachments:

    • Fibrous septa from skin anchor to periosteum of distal phalanx (stabilizing pulp pad).

    • Digital pulp and nail matrix adhere tightly to the dorsal and volar aspects.

Arterial Supply

  • Proper digital arteries (from the superficial palmar arch) form terminal branches supplying the distal phalanx, nail bed, and pulp.

  • Rich capillary loops within the pulp and periosteum provide abundant perfusion for healing.

Function

  • Support: Provides rigid base for nail and fingertip structures.

  • Dexterity: Enables precision grip and tactile manipulation.

  • Load bearing: Transmits forces during pinch and fine motor activities.

  • Attachment site: Anchors tendons and soft tissues essential for flexion and extension.

  • Protection: Shields underlying neurovascular structures and terminal sensory receptors.

Clinical Significance

  • Fractures: Common due to crush or tuft injuries; may involve nail bed lacerations or open fractures.

  • Mallet finger: Caused by avulsion of the extensor tendon from the dorsal base.

  • Tuft fractures: Involve the distal end; often comminuted but stable.

  • Osteomyelitis: Can occur after open injury or infection from distal soft tissues.

  • Subluxation/dislocation: May occur at the DIP joint following trauma.

  • Tumors: Enchondromas or subungual exostoses may affect the distal phalanx.

  • Imaging relevance: MRI and CT essential for evaluating fractures, infections, nail bed lesions, and soft tissue masses.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark).

    • Marrow: Bright, reflecting fatty marrow.

    • Articular surface (base): Intermediate-to-low signal cartilage.

    • Soft tissues: Nail bed appears thin and dark; pulp fat bright.

    • Pathology: Fractures = linear low-signal line; marrow edema = intermediate-to-bright signal intensity.

  • T2-weighted images:

    • Cortex: Dark, low signal.

    • Marrow: Bright, slightly less than on T1 but higher than surrounding muscle.

    • Cartilage and joint fluid: Intermediate-to-bright signal outlining the DIP joint.

    • Pathology: Bone contusion, fracture, or infection appears hyperintense; chronic sclerosis = low signal.

  • STIR:

    • Normal marrow: Intermediate-to-dark signal.

    • Abnormal marrow (edema/infection): Bright hyperintense signal extending into shaft or tuft.

    • Soft-tissue swelling or cellulitis: Diffuse hyperintensity in subcutaneous and pulp tissues.

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: Intermediate-to-dark signal with smooth cortical margins.

    • Abnormal: Bright focal or diffuse signal with trabecular pattern loss (edema, infection, fracture).

    • Excellent for detecting subtle fractures, bone bruising, or soft tissue abscesses.

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: Mild homogeneous enhancement of marrow and periosteum.

    • Osteomyelitis: Intense marrow enhancement with cortical disruption.

    • Abscess: Rim enhancement with central non-enhancing cavity.

    • Soft-tissue inflammation: Diffuse or focal enhancement of pulp, nail bed, or flexor tendon sheath.

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, sharply defined margins.

  • Trabecular bone: Fine internal network; marrow cavity clearly visualized.

  • Tuft: Expanded distal end, often flattened dorsally.

  • Pathology:

    • Fractures: visible as cortical breaks, comminution, or depressed fragments.

    • Osteophytes: small marginal bone spurs in degenerative changes.

    • Bone erosion or cortical destruction: seen in infection or neoplasm.

    • Nail bed calcification or foreign bodies may be visualized.

MRI images

distal phalanx of hand coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

distal phalanx of hand coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

CT image

distal phalanx of hand ct axial

CT image

distal phalanx of hand CT sagittal image

X Ray image

Distal phalanx of hand