The ulnocapitate ligament is the most superficial of the three extrinsic palmar ulnocarpal ligaments and a volar stabilizer of the ulnocarpal complex 1-3.
The ulnocapitate ligament is the only ulnocarpal ligament directly attaching to the ulnar head. It runs superficial to the ulnolunate and ulnotriquetral ligament reinforcing the palmar component of the lunotriquetral interosseous ligament. It connects the ulnar fovea to the capitate and interdigitates distally with fibers of the radioscaphocapitate ligament and fibers of the scaphotriquetral ligament, forming the palmar greater arc or arcuate ligament 1-3.
Distally ulnocapitate ligament inserts onto the body of the capitate 1-5.
The ulnocapitate ligament can be visualized on ultrasound with the transducer placed at the volar ulnar aspect of the wrist in the longitudinal plane slightly rotated radially towards the capitate bone. The long axis of the ligament is displayed as an echogenic, fibrillary structure coursing over the lunotriquetral joint and connecting the distal ulna to the capitate 2,3.
The ulnocapitate ligament is difficult to appreciate on MRI even with proper anatomic knowledge ref.
The ligament is most likely injured or involved in the following pathologic conditions 6:
- traumatic triangular fibrocartilage complex injury (Palmer 1c/1d)
- ulnar-sided perilunate instability
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