Dorsal Capitotrapezoid Ligament: Anatomy, Function, Imaging

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Dorsal capitotrapezoid ligament (Trapezocapitate ligament)

The dorsal capitotrapezoid ligament, also known as the trapezocapitate ligament, is a short, strong intercarpal ligament connecting the dorsal surfaces of the trapezoid and capitate bones in the distal carpal row of the wrist. It is part of the dorsal intercarpal ligament complex, which provides stability and coordination of carpal motion during wrist flexion and extension.

This ligament, along with its palmar counterpart, maintains midcarpal joint congruity and limits excessive translational movement between the trapezoid and capitate bones. It plays an essential role in carpal stability, particularly in transmitting axial and rotational forces across the distal carpal row.

Synonyms

Trapezocapitate ligament
Dorsal intercarpal trapezoid-capitate ligament

Location and Structure

The dorsal capitotrapezoid ligament extends obliquely from the dorsal surface of the trapezoid to the dorsal aspect of the capitate, forming part of the dorsal capsule of the midcarpal joint.
It lies superficial to the joint capsule and deep to the extensor tendons of the wrist.
The palmar capitotrapezoid ligament, its counterpart on the volar side, mirrors this configuration and reinforces the palmar aspect of the trapezocapitate articulation.

Attachments

Proximal attachment: Dorsal surface of the trapezoid bone near its distal articular margin.
Distal attachment: Dorsal surface of the capitate bone, blending with the midcarpal joint capsule.
Palmar attachment (for palmar ligament): From the palmar trapezoid surface to the palmar aspect of the capitate, forming part of the palmar intercarpal complex.

Relations

Dorsally: Covered by the extensor carpi radialis longus and brevis tendons and dorsal wrist fascia.
Palmarly: Related to the palmar capitotrapezoid ligament and flexor tendons within the carpal tunnel.
Medially: Adjacent to the capitohamate joint capsule and dorsal intercarpal ligaments.
Laterally: Continuous with the dorsal trapeziotrapezoid ligament.
Deep: Midcarpal joint space separating the trapezoid and capitate bones.

Function

Joint stabilization: Prevents dorsal translation of the capitate relative to the trapezoid.
Load transmission: Transfers compressive and torsional forces between the distal carpal bones.
Coordination of motion: Contributes to synchronized motion between trapezoid, capitate, and hamate during wrist flexion-extension.
Limitation of hypermobility: Restricts abnormal shearing or separation at the trapezocapitate articulation.

Clinical Significance

Ligament injury: Can occur in wrist sprains or hyperextension injuries, particularly with carpal instability.
Midcarpal instability: Disruption may contribute to dorsal intercalated segment instability (DISI) or midcarpal collapse.
Degeneration: Chronic overuse can cause attenuation, leading to pain or reduced grip strength.
Arthritis: Degeneration or capsular thickening may occur in osteoarthritis or following trauma.
Surgical relevance: Important during dorsal wrist arthroscopy and midcarpal fusion procedures.

MRI Appearance

T1-weighted images:
- Ligament appears as a thin, low-signal (dark) band connecting the trapezoid and capitate.
- Surrounded by bright fat signal providing contrast.
- Partial tear: focal thickening or discontinuity with intermediate signal.
- Adjacent marrow (trapezoid/capitate): bright fatty signal.
T2-weighted images:
- Intact ligament: low to intermediate signal (fibrous tissue).
- Tear or degeneration: bright hyperintense signal within or around ligament.
- Adjacent capsular thickening or fluid in midcarpal recesses may appear hyperintense.
STIR:
- Normal ligament: dark to intermediate signal.
- Edema or acute injury: bright hyperintense signal along ligament course or adjacent bone.
Proton Density Fat-Saturated (PD FS):
- Normal ligament: low to intermediate signal.
- Partial tear: focal hyperintense area indicating fiber disruption.
- Periligamentous fluid or capsular effusion visible as bright fluid signal.
T1 Fat-Sat Post-Contrast:
- Intact ligament: minimal enhancement.
- Inflammatory or degenerative changes: periligamentous enhancement.
- Chronic fibrosis: low-signal thickened ligament with peripheral enhancement.

CT Appearance

Non-Contrast CT:

Ligament not directly visualized but inferred by close apposition of trapezoid and capitate.
Subtle interosseous space may be appreciated between articular surfaces.
Degenerative changes: Subchondral sclerosis or small osteophytes.
Chronic injury: Widening of joint space or small cortical irregularities.

Post-Contrast CT (standard):

Capsular enhancement may indicate inflammation.
Surrounding fat planes and carpal bone surfaces well visualized for degenerative or traumatic changes.

CT Arthrography Appearance

Normal: Ligament appears as a thin low-density band between the trapezoid and capitate, separating dorsal and palmar joint compartments.
Contrast: Fills joint recesses but does not pass through the intact ligament.
Partial tear: Focal contrast seepage into dorsal recesses.
Complete tear: Contrast extends freely between trapezocapitate joint spaces, outlining irregular ligament margins.
Degeneration: Irregularity or thinning of ligament contour with pericapsular contrast tracking.

MRI image

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