Dorsal Capitohamate Ligament: Anatomy, Function, Imaging

Topic

Dorsal capitohamate ligament

The dorsal capitohamate ligament is a short, strong intracarpal ligament connecting the capitate and hamate bones on the dorsal surface of the wrist. Along with its palmar counterpart, it provides stability to the midcarpal joint, particularly the capitohamate articulation, which forms part of the distal carpal row.

The dorsal and palmar capitohamate ligaments function together to maintain carpal alignment, transmit forces during wrist motion, and contribute to rotational stability of the distal carpal row during gripping and flexion-extension movements.

Synonyms

Capitohamate intercarpal ligament (dorsal and palmar bands)
Dorsal carpal interosseous ligament (capitate–hamate portion)

Location and Structure

The capitohamate joint lies between the distal surface of the capitate and the proximal surface of the hamate.
The dorsal and palmar ligaments form part of the intercarpal ligament complex stabilizing the distal row of carpal bones.
The dorsal ligament is thinner but stronger in tensile resistance, while the palmar ligament is broader and more oblique.

Attachments

Dorsal Capitohamate Ligament:

Proximal attachment: Dorsal surface of the capitate, near its distal third.
Distal attachment: Dorsal ridge of the hamate, blending with adjacent dorsal intercarpal fibers.
Orientation: Oblique from lateral to medial, directed slightly proximally.

Palmar Capitohamate Ligament:

Proximal attachment: Palmar surface of the capitate near its distal aspect.
Distal attachment: Palmar surface of the hamate, adjacent to the hook.
Orientation: Broad and fan-shaped, running medially and slightly distally, reinforcing the palmar capsule.

Relations

Dorsal ligament: Lies deep to the extensor tendons of the wrist, particularly the extensor digitorum and extensor digiti minimi.
Palmar ligament: Lies deep to the flexor tendons and palmar carpal fascia, anterior to the midcarpal joint capsule.
Laterally: Adjacent to the capitotrapezoid ligament.
Medially: Continuous with the hamatometacarpal ligaments.
Deep surface: Reinforces the fibrous capsule of the midcarpal joint.

Function

Joint stabilization: Prevents excessive separation of capitate and hamate bones.
Load transmission: Transfers compressive and rotational forces across the midcarpal joint.
Kinematic coordination: Maintains synchronous motion of the distal carpal row during wrist flexion, extension, and deviation.
Protection: Reinforces dorsal and palmar capsules against shear and torsional stresses.

Clinical Significance

Ligament sprain or tear: May occur from hyperextension, twisting injuries, or repetitive strain.
Midcarpal instability: Partial or complete rupture may lead to instability between the capitate and hamate, altering wrist mechanics.
Degenerative changes: Chronic stress can lead to attenuation and capsular laxity, seen in athletes and manual workers.
Surgical relevance: Integrity is vital in midcarpal arthroscopy, wrist reconstruction, and proximal row carpectomy procedures.
Imaging importance: MRI and CT arthrography essential for assessing ligament continuity, fiber orientation, and associated chondral damage.

MRI Appearance

T1-weighted images:
- Ligament appears as a thin, low-signal (dark) band connecting capitate and hamate.
- Adjacent fat and bone marrow appear bright, providing contrast.
- Disruption or attenuation appears as focal discontinuity or intermediate signal.
T2-weighted images:
- Normal ligament: low signal (dark), sharply defined margins.
- Pathology: hyperintense (bright) linear or diffuse signal indicating partial tear, strain, or edema.
- Surrounding capsule and joint fluid appear bright, outlining ligament clearly.
STIR:
- Normal: low to intermediate signal.
- Acute injury: bright hyperintensity due to periligamentous edema or hemorrhage.
- Chronic scarring or degeneration: heterogeneous low-to-intermediate signal.
Proton Density Fat-Saturated (PD FS):
- Ligament: dark linear structure bridging the bones.
- Tear: bright intraligamentous signal with indistinct borders.
- Best sequence for identifying partial or complete ligament disruption.
T1 Fat-Sat Post-Contrast:
- Normal ligament: minimal enhancement.
- Inflamed capsule or torn edges: focal enhancement.
- Synovitis or post-traumatic scarring: diffuse periligamentous enhancement.

CT Appearance

Non-Contrast CT:

Ligament not directly visualized due to soft-tissue density but identifiable as a low-density band between capitate and hamate.
Bony margins of capitate and hamate are well-defined, showing the narrow midcarpal joint space.
Pathology:
- Small avulsion fragments or irregularity at attachment sites.
- Early degenerative changes: subchondral sclerosis or cystic changes.

Post-Contrast CT (standard):

Contrast outlines joint capsule but not the ligament directly.
Capsular enhancement may indicate inflammation or chronic strain.

CT Arthrography Appearance

Normal: Ligament appears as a thin, continuous low-density band bridging the capitate and hamate; contrast remains confined to joint spaces.
Partial tear: Contrast insinuates partially between ligament fibers, showing linear contrast extension or irregular outline.
Complete tear: Contrast passes freely between the capitate and hamate, outlining both articular surfaces and separating ligament margins.
Chronic degeneration: Thinning, irregular contour, and mild periligamentous contrast leakage.

Palmar Capitohamate Ligament (Imaging Notes)

On MRI and CT, the palmar ligament is broader and less distinct than the dorsal one.
Appears as a thick, low-signal band deep to the flexor tendons.
Partial tears show focal hyperintensity on PD FS and T2, while chronic fibrosis appears low-signal on all sequences.
CT arthrography shows contrast outlining the palmar joint surface but not extending beneath intact fibers.

MRI images

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