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Head of the phalanx (hand)

The head of the phalanx of the hand forms the distal articular end of each proximal or middle phalanx. It articulates with the base of the next phalanx, creating the interphalangeal joints—hinge-type synovial joints that permit flexion and extension of the fingers.

In the thumb, the head of the proximal phalanx articulates with the distal phalanx to form a single interphalangeal joint. In the other digits, proximal phalangeal heads articulate with middle phalanges, and middle phalangeal heads with distal ones. The phalangeal heads are rounded dorsally and flattened plantarly, covered with hyaline cartilage, and play a vital role in digital motion, grip strength, and precision movement.

Synonyms

  • Distal articular end of the phalanx

  • Phalangeal head

  • Condyle of the phalanx

Location and Structure

  • The head is the distal, rounded part of each proximal and middle phalanx.

  • Articular surface: Smooth, convex, and covered by hyaline cartilage for friction-free movement.

  • Neck: Narrow segment between shaft and head, commonly fractured in pediatric injuries.

  • Base of succeeding phalanx: Concave articular surface receives the head to form an interphalangeal joint.

  • The thumb phalanx head supports only one interphalangeal articulation, while other digits form both proximal and distal interphalangeal joints.

Relations

  • Dorsally: Extensor tendons and dorsal capsule of interphalangeal joint

  • Ventrally (palmar side): Flexor tendons, palmar plate, and digital fibro-osseous sheath

  • Laterally: Collateral ligaments

  • Proximally: Shaft and periosteum of phalanx

  • Distally: Base of the next phalanx

Attachments

  • Capsule: Fibrous capsule surrounding the head, reinforced dorsally and laterally

  • Collateral ligaments: Attach to the lateral aspects of the head and limit side-to-side deviation

  • Palmar plate: Thick fibrocartilaginous structure reinforcing the palmar aspect, prevents hyperextension

  • Tendons:

    • Dorsal: Extensor digitorum and extensor indicis (or pollicis longus in thumb) cross over dorsally

    • Palmar: Flexor digitorum profundus and flexor digitorum superficialis insert distally

Arterial Supply

  • Digital branches of the proper palmar digital arteries, arising from the superficial palmar arch and common digital arteries

Function

  • Joint motion: Allows flexion and extension at interphalangeal joints for precise hand movements

  • Force transmission: Distributes load between phalanges during gripping and fine motor activity

  • Stability: Provides anchor points for collateral ligaments and palmar plates

  • Shock absorption: Hyaline cartilage cushions compressive forces during manipulation and grasp

Clinical Significance

  • Fractures: Common in crush injuries, falls, or sports trauma—especially at the neck and condylar region

  • Dislocations: Frequently involve the interphalangeal joints; may cause collateral ligament rupture

  • Arthritis: Degenerative and post-traumatic changes affect joint congruency and motion

  • Osteochondral defects: May occur due to repetitive trauma or microvascular injury

  • Inflammatory arthropathy: Seen in rheumatoid arthritis, psoriatic arthritis, and gout

  • Imaging importance: MRI and CT are essential for assessing cortical continuity, joint congruence, and early cartilage or marrow changes

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark)

    • Marrow: Bright, due to fatty composition in adults

    • Articular cartilage: Smooth, thin intermediate-to-low signal cap over the phalangeal head

    • Joint capsule: Low signal lining joint contour

    • Pathology: Fracture lines—linear low-signal defects; bone contusions—focal intermediate signal

  • T2-weighted images:

    • Cortex: Low signal

    • Marrow: Bright, though slightly less intense than on T1

    • Cartilage: Intermediate-to-bright signal; surface irregularities indicate degeneration

    • Joint fluid: Bright hyperintense, outlining articular margins

    • Pathology: Edema, synovitis, and cartilage erosion appear hyperintense

  • STIR:

    • Normal marrow: Intermediate-to-dark signal

    • Pathologic marrow: Bright hyperintense in edema, fracture, or infection

    • Sensitive for early bone marrow and soft-tissue inflammation

  • Proton Density Fat-Saturated (PD FS):

    • Normal bone marrow: Intermediate-to-dark signal

    • Abnormal: Bright hyperintensity representing marrow edema, capsulitis, or ligament injury

    • Excellent for detecting small joint effusions and cartilage defects

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: Mild homogeneous enhancement

    • Synovitis or inflammation: Diffuse or nodular enhancement of synovium and capsule

    • Osteomyelitis: Irregular patchy marrow enhancement with cortical breach

    • Rheumatoid arthritis: Enhancing pannus along articular margins

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, well-defined smooth outline

  • Trabecular bone: Fine, regular internal structure

  • Articular surface: Convex, sharply demarcated by subchondral bone

  • Pathology:

    • Detects cortical fractures, erosions, and subchondral sclerosis

    • Visualizes early osteophyte formation and malalignment

    • Excellent for preoperative fracture mapping and post-fixation evaluation

MRI images

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

MRI images

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

CT image

Head of distal phalanx coronal ct image

CT image

Head of distal phalanx sag image