The ulnolunate ligament is one of the intracapsular, extrinsic palmar ulnocarpal ligaments and a component of the ulnocarpal complex 1-4.
The ulnolunate ligament forms the anterior part of the ulnocarpal joint capsule together with the ulnotriquetral ligament, with which it shares a common origin and attaches the volar radioulnar ligament and thus the triangular fibrocartilage complex to the ulnar side of the lunate 1-3.
The ulnolunate ligament originates together with the ulnotriquetral ligament from the volar radioulnar ligament 1-3.
The distal insertion of the ulnolunate ligament is the palmar surface of the lunate bone, blending with the distal fibers of the short radiolunate ligament 1-4.
The ulnolunate ligament can be visualized on ultrasound with the transducer placed at the volar ulnar aspect of the wrist in the longitudinal plane and slightly rotate towards the lunate. The long axis of the ligament is then displayed as an echogenic, fibrillary structure coursing over the ulnocarpal joint and connecting the volar radioulnar ligament to the lunate. Proximally it cannot be demarcated from the ulnotriquetral ligament 2,3.
The ulnolunate ligament can be visualized on MRI best on coronal or 3D images 4. With proper anatomical knowledge, it can be also variably seen on sagittal images. It has a hypointense, slightly striated appearance and is seen anterior to the medial ulnocarpal joint ref.
The ligament is most likely injured or involved in the following pathologic conditions 6-8:
- traumatic triangular fibrocartilage complex injuries
- ulnar-sided perilunate instability
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- 6. Oneson SR, Scales LM, Timins ME, Erickson SJ, Chamoy L. MR imaging interpretation of the Palmer classification of triangular fibrocartilage complex lesions. (1996) Radiographics : a review publication of the Radiological Society of North America, Inc. 16 (1): 97-106. doi:10.1148/radiographics.16.1.97 - Pubmed
- 7. von Borstel D, Wang M, Small K, Nozaki T, Yoshioka H. High-Resolution 3T MR Imaging of the Triangular Fibrocartilage Complex. (2017) Magnetic resonance in medical sciences : MRMS : an official journal of Japan Society of Magnetic Resonance in Medicine. 16 (1): 3-15. doi:10.2463/mrms.rev.2016-0011 - Pubmed
- 8. Murray PM, Palmer CG, Shin AY. The mechanism of ulnar-sided perilunate instability of the wrist: a cadaveric study and 6 clinical cases. (2012) The Journal of hand surgery. 37 (4): 721-8. doi:10.1016/j.jhsa.2012.01.015 - Pubmed