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Topic

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Nail (hand)

The hand nail (nail plate) is a hard, keratinized structure forming the dorsal protective covering of the distal phalanx. Together with the nail bed, matrix, hyponychium, and surrounding soft tissues, it constitutes the nail unit, which plays essential roles in fine motor function, tactile sensation, and protection of the fingertip.

The nail enhances pinch strength, stabilizes the pulp during grasping, and improves precision tasks. Its unique layered keratin structure and intimate attachment to the nail bed allow smooth growth and mechanical resistance.

Synonyms

  • Nail plate

  • Unguis

  • Finger nail

Location and Structure

  • Nail plate: Hard, translucent keratin plate lying dorsally over distal phalanx

  • Nail bed: Highly vascular epithelium beneath nail plate, giving the nail its pink color

  • Nail matrix: Proximal germinative epithelium producing keratin for nail growth

  • Lunula: Proximal whitish crescent region of the matrix, partially visible

  • Hyponychium: Skin–nail junction at distal free edge

  • Eponychium (cuticle): Proximal fold protecting nail root

  • Underlying bone: Tuberosity of the distal phalanx provides rigid support

Relations

  • Dorsally: Surrounding skin and dorsal nail fold

  • Ventrally: Nail bed and periosteum of distal phalanx

  • Proximally: Nail matrix and eponychium

  • Distally: Fingertip pulp and hyponychium

  • Laterally: Nail grooves and lateral nail folds

Attachments

  • Nail plate: Firmly adherent to nail bed via longitudinal epidermal ridges

  • Matrix: Anchored to dorsal surface of distal phalanx

  • Hyponychium: Secures nail plate at its free edge

  • Cuticle: Seals proximal nail fold

Function

  • Protects distal phalanx and fingertip pulp

  • Enhances precision grip and pinch strength

  • Assists in tactile sensitivity

  • Serves as a counterforce for pulp during object manipulation

  • Provides cosmetic and sensory roles

Clinical Significance

  • Nail deformity reflects systemic disease (e.g., anemia, psoriasis)

  • Trauma may produce subungual hematoma, nail avulsion, or distal phalanx fracture

  • Infections: paronychia, onychomycosis

  • Tumors: glomus tumor, subungual exostosis

  • Essential in evaluating fingertip injuries radiologically

MRI Appearance

T1-weighted images:

  • Nail plate: Low-to-intermediate signal, smooth and laminated

  • Nail bed: Intermediate signal, often brighter than plate

  • Distal phalanx: Bright fatty marrow with low-signal cortex

  • Nail folds: Soft tissue intermediate signal

  • Hyponychium: Intermediate signal with clear border against plate

T2-weighted images:

  • Nail plate: Low signal (dark), appearing as a thin laminated structure

  • Nail bed: Intermediate-to-bright signal due to vascularity

  • Soft tissues: Bright highlighting subcutaneous fat and pulp tissue

  • Bone cortex: Dark; bone marrow moderately bright

STIR:

  • Nail plate: Low-to-intermediate signal

  • Nail bed: Intermediate; vascular regions may appear brighter

  • Soft tissues: Fat suppressed, giving high contrast between muscle/pulp and bone

  • Distal phalanx: Bone marrow typically intermediate-to-dark

  • Good definition of nail plate, bed, and periungual soft tissues

T1 Fat-Saturated Post-Contrast:

  • Nail plate: No enhancement

  • Nail bed: Enhances uniformly due to rich vascular supply

  • Nail folds/cuticle: Mild enhancement

  • Underlying bone and soft tissue: Smooth enhancement pattern

  • Clear delineation of nail bed and matrix vascularity

CT Appearance

Non-Contrast CT:

  • Nail plate: Thin hyperdense structure compared to soft tissue

  • Nail bed: Soft-tissue density beneath plate

  • Distal phalanx: High-density cortical shell with lower-density cancellous bone

  • Provides excellent detail of subungual exostosis or fractures

MRI image

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MRI image

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