Topics

Topic

design image
Tubercle of trapezium bone

The tubercle of the trapezium is a prominent bony projection located on the palmar (anterior) surface of the trapezium bone, one of the distal row carpal bones in the wrist. It serves as an important attachment site for the flexor retinaculum and the abductor pollicis brevis muscle, both of which contribute to the formation and function of the thenar eminence.

This tubercle, together with the tubercle of the scaphoid, forms the radial (lateral) boundary of the carpal tunnel, making it a crucial landmark in both anatomical and surgical contexts. The prominence can be palpated just distal to the base of the thumb and is often visualized in wrist imaging studies assessing carpal tunnel or trapeziometacarpal (TMC) joint pathology.

Synonyms

  • Trapezial tubercle

  • Anterior tubercle of the trapezium

  • Palmar tubercle of trapezium

Location and Structure

  • Position: Palmar aspect of the trapezium bone, on its radial side near the base of the first metacarpal.

  • Shape: Rounded or ridge-like bony eminence.

  • Orientation: Projects anteriorly and slightly laterally.

  • Composition: Compact cortical bone externally, enclosing cancellous bone internally.

  • Relations: Lies superficial to the flexor retinaculum and beneath the thenar skin crease.

Relations

  • Anteriorly: Flexor retinaculum and abductor pollicis brevis tendon

  • Posteriorly: Trapezium body and its articular surfaces for the first metacarpal and scaphoid

  • Laterally: Radial artery as it curves dorsally toward the anatomical snuffbox

  • Medially: Tubercle of scaphoid (forming lateral wall of carpal tunnel)

  • Superiorly: Base of the first metacarpal

  • Inferiorly: Proximal portion of the trapezium bone body

Attachments

  • Flexor retinaculum: Attaches along the medial aspect of the tubercle, forming part of the radial border of the carpal tunnel.

  • Abductor pollicis brevis: Originates from the palmar surface and tubercle of the trapezium, forming one of the superficial thenar muscles.

  • Joint capsule: Fibrous tissue of the trapeziometacarpal joint blends posteriorly with the periosteum near the tubercle.

Function

  • Structural support: Provides leverage and attachment for thenar muscles controlling thumb motion.

  • Carpal tunnel boundary: Contributes to the lateral wall of the carpal tunnel along with the scaphoid tubercle.

  • Biomechanical role: Acts as a stable anchor point for the flexor retinaculum and muscles facilitating opposition and abduction of the thumb.

  • Clinical landmark: Palpable during carpal tunnel release or trapezium excision surgeries.

Clinical Significance

  • Fractures: Avulsion or stress fractures may occur due to tension from the flexor retinaculum or trauma to the radial palm.

  • Osteoarthritis: Frequently involved in degenerative changes at the trapeziometacarpal (thumb basal) joint.

  • Carpal tunnel syndrome: Tubercle serves as a surgical landmark for identifying radial tunnel boundaries during decompression.

  • Accessory ossicles: Small sesamoid-like ossifications near the tubercle may mimic fracture on imaging.

  • Palpation importance: Easily identifiable on the radial aspect of the wrist, just distal to the scaphoid tubercle.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark) outlining the tubercle.

    • Bone marrow: Bright due to fatty composition in adults.

    • Muscle and tendon attachments: Intermediate-to-low signal, sharply demarcated.

    • Fracture lines: Appear as linear low-signal defects through cortex or cancellous bone.

    • Peritubercular fat: Bright, providing contrast against cortical margins.

  • T2-weighted images:

    • Cortex: Low signal (dark).

    • Marrow: Bright, slightly less intense than T1 but higher than muscle.

    • Cartilage or fibrocartilage insertions: Intermediate-to-bright signal intensity.

    • Pathology: Bone marrow edema, fracture, or inflammation appears hyperintense relative to normal marrow.

  • STIR:

    • Normal tubercle and marrow: Intermediate-to-dark signal.

    • Pathologic regions: Bright hyperintense signal in fracture, edema, or inflammatory processes.

    • Useful for detecting occult bone injury or early osteitis.

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: Intermediate-to-dark with uniform trabecular pattern.

    • Abnormal: Bright hyperintense signal in bone marrow or soft-tissue edema adjacent to tubercle.

    • Excellent for assessing subtle cortical disruptions and peritendinous inflammation.

  • T1 Fat-Sat Post-Contrast:

    • Normal: Homogeneous mild enhancement of cancellous bone and soft tissues.

    • Pathology: Enhanced peritubercular soft tissue or bone marrow enhancement in osteitis, stress injury, or post-traumatic edema.

    • Osteomyelitis or synovitis: Show intense, patchy enhancement near joint surfaces.

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, sharply marginated bony outline.

  • Trabecular bone: Fine, homogeneous trabecular density within tubercle.

  • Articular margins: Smooth and well-defined; helps delineate trapezium-scaphoid and trapezium–first metacarpal articulations.

CT VRT 3D image

Tubercle of trapezium bone bone axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT VRT 3D image

Tubercle of trapezium bone sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Tubercle of trapezium bone ct axial

CT VRT image

Tubercle of trapezium bone 3d coronal cross sectional anatomy ct radiology image-img-00000-00000