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Head of metacarpal bone

The head of the metacarpal bone forms the distal rounded end of each metacarpal and articulates with the base of the proximal phalanx to create the metacarpophalangeal (MCP) joint. It is a convex articular surface covered with hyaline cartilage that allows smooth motion for flexion, extension, abduction, and adduction of the fingers. The metacarpal heads are prominent dorsally, forming the knuckles visible when the fist is clenched.

The metacarpal head plays a key role in grip strength, load distribution, and fine finger control. It is stabilized by the joint capsule, collateral ligaments, and volar plate, and receives insertions from tendons that control finger movement.

Synonyms

  • Distal articular end of the metacarpal

  • Metacarpal condyle

  • Head of the hand bone

Location and Structure

  • Located at the distal end of each metacarpal shaft, articulating with the base of the proximal phalanx.

  • The articular surface is rounded dorsopalmarly and wider anteriorly, ensuring joint stability in flexion.

  • Cartilage covering: Thick hyaline cartilage layer allows smooth articulation.

  • Neck: Slight constriction proximal to the head; a common site of fractures, especially in the fifth metacarpal (“boxer’s fracture”).

  • The dorsal aspect is subcutaneous, forming the knuckles, while the palmar aspect is reinforced by the volar plate and ligaments.

Relations

  • Dorsally: Extensor tendons of the corresponding digit

  • Palmarly: Joint capsule, volar plate, and flexor tendons within their fibrous sheaths

  • Laterally and medially: Collateral ligaments of the metacarpophalangeal joint

  • Proximally: Metacarpal neck and shaft

  • Distally: Base of the proximal phalanx

Attachments

  • Capsular attachment: Fibrous capsule encloses the metacarpophalangeal joint and attaches near the articular margins of the head.

  • Collateral ligaments: Arise from the sides of the head and insert into the base of the proximal phalanx and volar plate.

  • Volar plate: Thick fibrocartilaginous structure attached to the palmar aspect of the metacarpal head, preventing hyperextension.

  • Tendinous relations:

    • Dorsal: Extensor digitorum and extensor indicis or extensor digiti minimi tendons.

    • Palmar: Flexor digitorum superficialis and profundus tendons cross the joint to insert on the phalanges.

    • Collateral: Lumbrical and interosseous muscles insert near the base of the proximal phalanx, assisting in MCP flexion and extension control.

Function

  • Joint motion: Forms the MCP joint allowing flexion, extension, abduction, and adduction of digits.

  • Load transfer: Distributes forces from the proximal phalanx to the metacarpal shaft during grip and weight-bearing.

  • Grip and precision: Provides mechanical advantage for finger flexors during gripping or fine manipulation.

  • Structural support: Maintains alignment and curvature of the palmar arch for efficient hand function.

Clinical Significance

  • Fractures: Common at the metacarpal neck (especially fifth metacarpal) due to axial impact; intra-articular head fractures affect joint congruity.

  • Arthritis: Degenerative or post-traumatic arthritis may cause joint stiffness and deformity.

  • Dislocations: MCP joint dislocations can occur with hyperextension or direct trauma.

  • Osteochondral lesions: Damage to the cartilage or subchondral bone can lead to pain and instability.

  • Inflammatory disease: Rheumatoid arthritis frequently involves MCP joints, causing synovial proliferation and erosion of metacarpal heads.

  • Imaging relevance: MRI and CT play critical roles in evaluating cartilage, fractures, erosions, and post-surgical outcomes.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark)

    • Bone marrow: Bright fatty signal in normal adults

    • Articular cartilage: Smooth, thin intermediate-to-low signal covering the head

    • Joint capsule and ligaments: Low-signal bands outlining joint margins

    • Fracture lines: Linear low-signal lines crossing subchondral or cortical bone

    • Marrow pathology: Edema or contusion appears as patchy intermediate signal replacing normal bright marrow

  • T2-weighted images:

    • Cortex: Dark, low signal

    • Bone marrow: Bright (fat and vascular content), slightly less intense than on T1

    • Cartilage: Intermediate-to-bright; irregular or thinned cartilage suggests degeneration

    • Joint fluid: Hyperintense outlining articular surfaces

    • Pathology: Edema, synovitis, or chondral defects appear as bright areas

  • STIR:

    • Normal marrow: Intermediate-to-dark signal

    • Pathologic marrow: Bright hyperintense signal indicating edema, inflammation, or fracture

    • Excellent for early detection of stress injury, infection, or bone contusion

  • Proton Density Fat-Saturated (PD FS):

    • Normal head and marrow: Intermediate-to-dark signal intensity

    • Pathologic areas: Bright hyperintensity in marrow, cartilage, or pericapsular tissues indicating edema or inflammation

    • Ideal for evaluating ligamentous attachments, cartilage defects, and subtle fractures

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: Mild, homogeneous enhancement

    • Synovial inflammation: Diffuse or marginal enhancement

    • Osteomyelitis: Irregular, patchy enhancement extending into soft tissues

    • Arthritis: Thickened synovium with strong enhancement and possible erosions

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, sharply defined

  • Trabecular bone: Fine lattice structure visible within head

  • Articular surface: Smooth, well-corticated convex surface with visible subchondral bone

  • Pathology: Detects fractures, erosions, subchondral cysts, or osteophytes

  • Neck fractures: Commonly visualized as cortical disruptions proximal to the head

CT VRT 3D image

Head of metacarpal bone CT 3D VRT image -img-00000-00000

MRI image

Head of metacarpal bone coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Head of metacarpal bone ct coronal image

CT image

Head of metacarpal bone ct sag image