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Capitotrapezoid ligament (Trapezocapitate ligament)

The capitotrapezoid ligament, also known as the trapezocapitate ligament, is a strong fibrous band connecting the capitate and trapezoid bones within the distal carpal row of the wrist. It is part of the midcarpal interosseous ligament complex, stabilizing the junction between the central and radial carpal columns.

This ligament exists in two distinct portions — dorsal and palmar (volar) — each providing stability and coordinated motion between the trapezoid and capitate bones during wrist flexion, extension, and radial or ulnar deviation. It plays a crucial role in wrist kinematics, carpal integrity, and force transmission between the radial and central carpal segments.

Synonyms

  • Trapezocapitate ligament

  • Capitotrapezoid interosseous ligament

  • Trapezoid-capitate ligament

Location and Structure

  • Location: Between the trapezoid (radially) and the capitate (centrally) in the distal carpal row.

  • Composition: Dense fibrous connective tissue forming dorsal and palmar bands; occasionally a thin interosseous portion.

  • Orientation: Oblique and horizontal fibers joining adjacent carpal surfaces, contributing to the midcarpal stability.

  • Joint relation: Strengthens the midcarpal joint capsule between the trapezoid and capitate bones.

Dorsal Capitotrapezoid Ligament

  • Located on the dorsal aspect of the midcarpal joint, extending obliquely from the dorsal surface of the trapezoid to the dorsal surface of the capitate.

  • Fibers blend with the dorsal intercarpal ligament, contributing to posterior wrist stability.

  • Taut in wrist flexion, limiting excessive motion and maintaining dorsal carpal alignment.

Palmar (Volar) Capitotrapezoid Ligament

  • Lies on the palmar aspect of the midcarpal joint, extending from the palmar surface of the trapezoid to the palmar surface of the capitate.

  • Continuous with fibers of the palmar intercarpal ligament and capitohamate ligament.

  • Taut in wrist extension, stabilizing the carpal arch and maintaining the curvature of the palmar carpal row.

Relations

  • Dorsally: Dorsal intercarpal ligament, extensor tendons of the wrist

  • Palmarly: Palmar intercarpal ligament, flexor tendons within the carpal tunnel

  • Laterally: Trapezium and second metacarpal base

  • Medially: Capitate and hamate articulation

  • Deep surface: Joint capsule and articular cartilage of the trapezoid-capitate joint

Attachments

  • Proximal attachment: Dorsal and palmar surfaces of the trapezoid bone

  • Distal attachment: Corresponding surfaces of the capitate bone

  • Blending: Fibers integrate with midcarpal joint capsule and adjacent interosseous ligaments

Function

  • Stabilization: Maintains firm articulation between trapezoid and capitate, contributing to distal carpal row integrity

  • Load transfer: Distributes compressive and shear forces across the midcarpal joint

  • Kinematic coordination: Enables synchronized movement between radial and central carpal columns during wrist motion

  • Support: Reinforces dorsal and palmar carpal arches, resisting translational displacement

  • Prevention of carpal instability: Helps prevent separation or malalignment of the trapezoid-capitate junction in trauma or ligament injury

Clinical Significance

  • Injury: Rarely isolated; may occur with midcarpal or perilunate instability and dorsal intercarpal ligament sprains

  • Degeneration: Chronic repetitive wrist stress (e.g., in athletes or manual labor) can cause fibrous thickening or partial tear

  • Arthritis: Degenerative or post-traumatic changes at the trapezoid-capitate joint may involve this ligament

  • Surgical importance: Identified in carpal reconstruction or wrist arthrodesis procedures

  • Imaging role: Crucial for evaluation of midcarpal stability and intercarpal ligament injuries on MRI and CT arthrography

MRI Appearance

  • T1-weighted images:

    • Ligament: low signal (dark) linear band between trapezoid and capitate

    • Adjacent bone marrow: bright fatty signal

    • Tears or degeneration: focal discontinuity or intermediate signal intensity replacing the normal dark band

  • T2-weighted images:

    • Normal ligament: low signal (dark) structure

    • Pathology: hyperintense signal in partial or complete tears, with adjacent bone marrow edema or synovial reaction

    • Fluid or joint effusion: bright hyperintense surrounding the ligament margins

  • STIR:

    • Ligament: intermediate-to-dark signal

    • Pathology: bright hyperintense zones indicating edema or partial disruption

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: dark linear band with well-defined borders

    • Partial tears: focal bright signal at attachment sites or within substance

    • Useful for detecting degenerative fraying or subtle edema

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: no significant enhancement

    • Pathologic: enhancing margins or periligamentous enhancement due to synovitis, inflammation, or scarring

CT Appearance

Non-Contrast CT:

  • Ligament not distinctly visualized due to soft-tissue density

  • Indirect visualization by assessing joint spacing, cortical contour, and alignment between trapezoid and capitate

  • Degeneration or calcification may appear as fine dense linear opacities

Post-Contrast CT (standard):

  • Soft-tissue enhancement highlights inflamed or fibrotic ligament margins

  • Used for assessing post-traumatic fibrosis or arthritic changes around the midcarpal joint

CT Arthrography Appearance

  • Intra-articular contrast outlines the trapezoid-capitate joint, delineating the dorsal and palmar ligament attachments

  • Normal ligament: thin non-enhancing low-density band separating contrast-filled joint spaces

  • Tear or defect: contrast leakage between adjacent carpal compartments or extension through ligament substance

  • Partial tear: irregular contrast tracking along the ligament margin

  • Complete tear: free communication between midcarpal and carpometacarpal joint spaces

  • Excellent for assessing subtle intercarpal instability and post-traumatic carpal pathology

MRI images

Capitotrapezoid (Trapezocapitate) Ligament mri axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Capitotrapezoid (Trapezocapitate) Ligament mri axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

Capitotrapezoid (Trapezocapitate) Ligament mri coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Capitotrapezoid (Trapezocapitate) Ligament mri coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001