Topics

Topic

design image
Metacarpal bones

The metacarpal bones form the intermediate skeletal structure of the hand, connecting the carpal bones of the wrist to the phalanges of the fingers. There are five metacarpals, numbered I to V from lateral (thumb) to medial (little finger). Each consists of a base (proximal end), shaft (body), and head (distal end).

They create the framework for the palm of the hand and play a vital role in grip strength, dexterity, and load transmission. Each metacarpal articulates proximally with the carpal bones and distally with the proximal phalanges to form the metacarpophalangeal (MCP) joints.

Synonyms

  • Bones of the palm

  • Metacarpus

  • Hand metacarpal skeleton

Location and Structure

  • The five metacarpals extend between the carpus and proximal phalanges.

  • Base (proximal end): Articulates with carpal bones (trapezium, trapezoid, capitate, hamate).

  • Head (distal end): Rounded and covered with articular cartilage, forming MCP joints.

  • Shaft (body): Slightly curved, with dorsal convexity and palmar concavity.

  • First metacarpal: Shortest and thickest, articulates with the trapezium, forming a saddle joint allowing thumb opposition.

  • Second to fifth metacarpals: Progressively longer; bases articulate with adjacent metacarpals forming the carpometacarpal (CMC) joints.

Relations

  • Proximally: Carpal bones of the wrist

  • Distally: Proximal phalanges of the fingers

  • Dorsally: Extensor tendons, dorsal interossei muscles, and dorsal veins of the hand

  • Palmarly: Flexor tendons, lumbricals, and palmar interossei muscles

  • Laterally and medially: Adjacent metacarpals connected by interosseous ligaments

Attachments

  • Muscles attaching to bases and shafts:

    • Flexor carpi radialis, extensor carpi radialis longus and brevis, extensor carpi ulnaris

    • Dorsal and palmar interossei muscles originate from metacarpal shafts

    • Adductor pollicis and opponens pollicis insert on the first metacarpal

  • Ligamentous attachments:

    • Strong palmar and dorsal metacarpal ligaments

    • Deep transverse metacarpal ligament connecting the distal metacarpal heads

Arterial Supply

  • Dorsal and palmar metacarpal arteries derived from the dorsal carpal arch and superficial/deep palmar arches

Function

  • Structural support: Form the skeleton of the palm, maintaining hand shape

  • Articulation: Contribute to CMC and MCP joints allowing finger flexion, extension, abduction, and adduction

  • Force transmission: Transfer loads from phalanges to carpus during grasping and pushing

  • Leverage: Serve as levers for intrinsic and extrinsic muscles controlling fine hand movements

Clinical Significance

  • Fractures: Common injuries; include boxer’s fracture (5th metacarpal neck) and Bennett’s or Rolando fractures (1st metacarpal base)

  • Osteoarthritis: Common at the thumb CMC joint (1st metacarpal-trapezium articulation)

  • Infections and tumors: Osteomyelitis or enchondromas may involve metacarpal shafts

  • Congenital variations: Synostosis or shortening may occur in syndromic hand deformities

  • Post-traumatic deformity: Malunion may affect grip and finger alignment

  • Imaging importance: Critical for fracture detection, alignment assessment, and surgical planning

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark, sharply defined)

    • Marrow: Bright signal due to fatty marrow content in adults

    • Periosteum and ligaments: Low signal thin margins around bone

    • Fractures: Linear low-signal line through bright marrow

    • Pathology: Replacement of bright marrow by intermediate or dark signal in tumor or infection

  • T2-weighted images:

    • Cortex: Low signal (dark)

    • Marrow: Bright, though slightly less than on T1

    • Cartilage: Intermediate-to-bright at MCP and CMC joint surfaces

    • Edema or inflammation: Focal or diffuse bright hyperintense signal replacing marrow fat

    • Joint fluid: Hyperintense outlining MCP joints

  • STIR:

    • Normal marrow: Intermediate-to-dark signal intensity

    • Pathology: Bright hyperintense areas in fractures, contusions, osteomyelitis, or marrow edema

    • Highly sensitive for early bone or soft-tissue inflammatory change

  • Proton Density Fat-Saturated (PD FS):

    • Normal bone: Intermediate-to-dark homogeneous signal

    • Abnormal: Focal bright hyperintensity indicating marrow or soft-tissue edema

    • Ideal for detecting subtle stress fractures, ligament injuries, and periosteal reaction

  • T1 Fat-Sat Post-Contrast:

    • Normal marrow: Mild uniform enhancement

    • Infection or inflammation: Patchy or peripheral enhancement

    • Tumor: Irregular, nodular, or diffuse enhancement

    • Post-surgical change: Linear enhancement along bone or soft-tissue scar

CT Appearance

Non-Contrast CT:

  • Cortex: Dense, high-attenuation margins with smooth continuity

  • Trabecular bone: Fine, reticulated pattern visible in medullary cavity

  • Fractures: Clear cortical disruption or displacement, even when subtle on radiographs

  • Deformities: Angular or rotational malalignment easily assessed in 3D reconstructions

  • Degenerative changes: Joint-space narrowing, subchondral sclerosis, and osteophytes visualized with precision

CT VRT 3D image

metacarpal boneS CT 3D VRT image

MRI image

metacarpal bones ct coronal

CT image

metacarpal bones coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

metacarpal bones coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001