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Palmar trapeziotrapezoid ligament

The palmar trapeziotrapezoid ligament is a strong intrinsic ligament of the wrist that connects the palmar (volar) surfaces of the trapezium and trapezoid bones. It forms part of the trapeziotrapezoid joint capsule, which is one of the midcarpal joints in the distal carpal row. This ligament contributes to the stability of the radial carpal column, supporting the articulation between the trapezium, trapezoid, and base of the second metacarpal.

Together with its dorsal counterpart—the dorsal trapeziotrapezoid ligament—it maintains firm articulation between these small but crucial carpal bones during thumb and wrist movements. The palmar ligament is typically thicker and stronger than the dorsal ligament, resisting hyperextension and rotational stress during gripping and thumb opposition.

Synonyms

  • Volar trapeziotrapezoid ligament

  • Trapezium–trapezoid palmar ligament

  • Palmar intercarpal ligament (trapezium–trapezoid portion)

Location and Structure

  • The ligament spans between the palmar surfaces of the trapezium and trapezoid bones, lying deep to the flexor carpi radialis tendon and palmar carpal fascia.

  • Composed of dense collagen fibers, oriented transversely and slightly obliquely, reinforcing the anterior aspect of the joint capsule.

  • The dorsal trapeziotrapezoid ligament lies on the opposite (dorsal) side and is thinner, allowing limited carpal gliding motion.

Attachments

  • Proximal attachment: Palmar surface of the trapezium bone, near its articular margin.

  • Distal attachment: Palmar surface of the trapezoid bone, along the adjacent joint capsule.

  • The ligament often blends with capsular fibers of the trapeziotrapezoid joint and with the palmar carpometacarpal ligaments to the base of the second metacarpal.

Relations

  • Superficial (anterior): Flexor carpi radialis tendon, palmar carpal fascia, and skin of the volar wrist.

  • Deep (posterior): Articular surfaces of the trapezium and trapezoid bones forming the trapeziotrapezoid joint.

  • Lateral: Radial artery (laterally positioned but excluded from vascular description).

  • Medial: Palmar ligaments of the trapezoid–capitate articulation.

Function

  • Joint stabilization: Provides strong palmar reinforcement to the trapeziotrapezoid joint.

  • Load transmission: Helps distribute compressive forces from the thumb and index finger during gripping.

  • Motion control: Restricts excessive dorsal translation and palmar separation of the trapezium and trapezoid.

  • Support of radial column: Contributes to carpal integrity with the trapeziometacarpal joint, ensuring stable thumb movement.

Clinical Significance

  • Ligament injury or sprain: May occur in wrist hyperextension or repetitive loading injuries; often associated with pain at the base of the thumb and wrist.

  • Degeneration: Common in early carpometacarpal osteoarthritis; degeneration can cause joint instability or subluxation.

  • Arthritis: Trapeziotrapezoid joint osteoarthritis leads to thickening and fibrosis of the ligament.

  • Surgical relevance: Important in basal thumb surgery, wrist fusion, and ligament reconstruction procedures.

  • Imaging role: Crucial for assessing carpal instability, ligament tears, or post-traumatic arthropathy on MRI or CT arthrograms.

MRI Appearance

  • T1-weighted images:

    • Ligament: low signal (dark band) connecting the palmar surfaces of the trapezium and trapezoid.

    • Adjacent bone marrow: bright (fatty signal) providing contrast.

    • Joint space: thin dark line with bright surrounding fat.

    • Chronic degeneration: thickened, irregular low-to-intermediate signal.

  • T2-weighted images:

    • Normal ligament: low signal, sharply defined margins.

    • Partial tear: focal bright hyperintensity within the ligament fibers.

    • Complete tear: discontinuity or nonvisualization with adjacent joint effusion.

    • Surrounding soft tissue edema appears bright hyperintense.

  • STIR:

    • Ligament: dark-to-intermediate signal intensity.

    • Pathology: hyperintense regions adjacent to ligament in acute sprain or synovitis.

    • Excellent for early detection of inflammatory and traumatic changes.

  • Proton Density Fat-Saturated (PD FS):

    • Normal: dark, well-defined band between trapezium and trapezoid.

    • Partial tears or inflammation: bright intraligamentous or periligamentous signal.

    • Best for subtle ligament strain and joint fluid visualization.

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: minimal enhancement.

    • Synovitis or inflammatory degeneration: periligamentous enhancement.

    • Scar tissue or fibrosis: heterogeneous mild enhancement.

CT Appearance

Non-Contrast CT:

  • Ligament not directly visible but seen as a thin soft-tissue band between dense trapezial cortices.

  • Articular surfaces: smooth and congruent in normal cases.

  • Degenerative changes: joint space narrowing, subchondral sclerosis, or marginal osteophytes.

  • Fracture or dislocation: disruption of articular alignment or adjacent cortical irregularity.

Post-Contrast CT (standard):

  • Capsule and ligament may show enhancing soft-tissue thickening in inflammation.

  • Useful for detecting periarticular fibrosis or subtle joint effusion.

CT Arthrography Appearance

  • Normal: Contrast outlines the trapeziotrapezoid joint space clearly; the ligament appears as a thin, non-opacified low-density band across the palmar joint margin.

  • Partial tear: Small contrast extension into or around the palmar ligament.

  • Complete tear: Contrast extravasation beyond the palmar margin, outlining disrupted fibers.

  • Degenerative change: Irregular joint contour with contrast tracking into small recesses or subchondral defects.

  • Post-surgical or arthritic state: Thickened irregular ligament with reduced joint space and periarticular sclerosis.

MRI image

Palmar trapeziotrapezoid ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000