Topics

Topic

design image
Scaphoid

The scaphoid bone is a boat-shaped carpal bone located on the radial (lateral) side of the proximal carpal row of the wrist. It bridges both carpal rows and plays a crucial role in wrist stability and motion. The scaphoid articulates with the radius proximally, the lunate medially, and the trapezium and trapezoid distally.

It is the largest bone of the proximal carpal row and serves as a mechanical link between the proximal and distal rows. Due to its unique retrograde blood supply, it is prone to avascular necrosis (AVN) after fracture, especially through the waist region.

Synonyms

  • Navicular bone of the hand

  • Carpal scaphoid

Location and Structure

  • Position: Radial side of wrist, forming the floor of the anatomical snuffbox.

  • Shape: Boat-shaped with a concave surface on one side and a convex surface on the other.

  • Surfaces:

    • Superior (proximal): Convex, articulates with the radius.

    • Inferior (distal): Concave, articulates with the trapezium and trapezoid.

    • Medial: Articulates with lunate proximally and capitate distally.

    • Lateral: Narrow ridge for attachment of the flexor retinaculum.

    • Dorsal: Narrow and rough for ligamentous attachment.

    • Palmar (volar): Prominent tubercle palpable at wrist crease.

  • Parts: Divided into proximal pole, waist, and distal pole — the waist being the most common fracture site.

Relations

  • Proximally: Radius (radiocarpal joint)

  • Distally: Trapezium and trapezoid

  • Medially: Lunate and capitate

  • Laterally: Radial artery and anatomical snuffbox tendons (extensor pollicis longus and brevis, abductor pollicis longus)

  • Anteriorly: Flexor retinaculum and scaphoid tubercle (palpable landmark)

Attachments

  • Flexor retinaculum: Attaches to scaphoid tubercle and trapezium forming the carpal tunnel roof.

  • Ligaments:

    • Scapholunate ligament (superiorly)

    • Radioscaphoid and scaphocapitate ligaments (anteriorly)

    • Radioscapholunate ligament (posteriorly)

  • Joint capsule: Attaches around articular margins.

Blood Supply

  • Dorsal carpal branch of the radial artery (primary source): enters distally and supplies proximal pole via retrograde flow.

  • Palmar branches of radial artery: supply distal pole and tubercle region.

  • The waist region has poor vascularity, predisposing it to nonunion and AVN after fracture.

Function

  • Wrist stability: Acts as a mechanical link between proximal and distal carpal rows.

  • Force transmission: Transfers load from hand to radius during grip and weight-bearing.

  • Motion control: Allows coordinated flexion and extension across radiocarpal and midcarpal joints.

  • Dynamic pivot: Facilitates smooth wrist movements during radial and ulnar deviation.

Clinical Significance

  • Fracture: Most commonly fractured carpal bone, typically at the waist. Mechanism: fall on outstretched hand (FOOSH).

  • Avascular necrosis: Common complication due to retrograde blood supply, particularly affecting proximal pole.

  • Nonunion: May lead to carpal instability and degenerative arthritis (scaphoid nonunion advanced collapse, SNAC wrist).

  • Tenderness in snuffbox: Key clinical sign of scaphoid fracture.

  • Delayed diagnosis: Initial radiographs can appear normal; MRI or CT essential for early detection.

  • Surgical relevance: Screw fixation or bone grafting may be required for unstable or nonunited fractures.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark).

    • Marrow: Bright fatty signal in normal bone.

    • Fracture line: Linear low-signal line crossing cortex or waist.

    • AVN: Low signal in proximal pole with loss of normal fatty brightness.

    • Post-fracture edema: Focal or diffuse intermediate-to-bright signal replacing normal marrow.

  • T2-weighted images:

    • Cortex: Low signal.

    • Marrow: Bright, slightly less than fat but higher than muscle.

    • Fracture or bone bruise: Linear or patchy hyperintense areas within the waist or pole.

    • AVN: May show mixed low and high signals due to necrosis and granulation tissue.

  • STIR:

    • Normal scaphoid: Intermediate-to-dark signal.

    • Fracture or marrow edema: Bright hyperintense signal at fracture site or proximal pole.

    • Excellent for early occult fractures or stress injuries.

  • Proton Density Fat-Saturated (PD FS):

    • Normal: Intermediate-to-dark homogeneous signal.

    • Fracture: Bright hyperintense line through cortex or trabeculae.

    • Edema: Focal bright signal within bone or surrounding soft tissue.

    • AVN: Mixed low-signal central necrosis and high-signal reactive zone.

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: Mild homogeneous enhancement.

    • AVN: Non-enhancing necrotic zone with peripheral enhancement.

    • Fracture healing: Enhancement along fracture line due to granulation tissue.

    • Infection or inflammation: Diffuse enhancement with soft-tissue involvement.

CT Appearance

Non-Contrast CT:

  • Cortex: High-density, sharply defined.

  • Trabecular pattern: Fine honeycomb architecture.

  • Fracture: Linear lucency or cortical break, best seen on sagittal and coronal reconstructions.

  • AVN: Sclerosis and trabecular collapse in proximal pole.

  • Nonunion: Visible fracture gap, cystic changes, or sclerosis at margins.

  • Useful for: Fracture classification, assessing healing, and surgical planning.

CT VRT 3D image

Scaphoid bone CT 3D VRT image -img-00000-00000

MRI image

Scaphoid axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

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

MRI image

Scaphoid sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Scaphoid ct coronal image