There have been many studies and classifications of the complex network of ligaments on the ulnar side of the wrist.
Comparing various authors’ interpretations of the anatomy of terminology of this region,
there is little consensus and no universal agreement.
A review by Brown,
et al.
quickly notes the different terminology used by different authors’ classifications to describe the ligaments of the wrist.1 Hogikyan showed the existence of an ulnar collateral ligament (UCL) at that originates in the ulnar styloid,
blends with the triangular fibrocartilage complex (TFCC) and meniscus,
continuing distally to attach to the triquetrum and hamate,
terminating at the base of the fifth metacarpal.2 Bogumil similarly indicates the UCL beginning at the base and body of the ulnar styloid,
extending distally to attach to the pisiform,
transverse carpal ligament,
and triquetrum,
finally attaching to the hamate and terminating the base of the fifth metacarpal.3 On the other hand,
some investigators used different terminology to describe a ligament in this area of the wrist,
most notably describing the UCL as part of the TFCC.4,5 Ishii uses the term “ulnar capsule” which spans the border of the TFCC from the ulnotriquetral ligament palmarly to the sheath of the extensor carpi ulnaris dorsally,
blending on the dorsal ulnar aspect of the ulnar styloid.6 Palmer et al.
also describe the UCL as part of the larger TFCC,
noting the presence of fibers arising from the ulnar aspect of the ulnar styloid (calling this the UCL),
and ultimately inserting distally into the triquetrum,
hamate,
and base of the fifth metacarpal.7 They note that the difference between the TFCC and a separate UCL is “not merely a matter of semantics”,
and that these two structures cannot be separated from one another.
Finally,
there are authors like who do not believe that the UCL exists as an independent structure,
noting that this distinction may be an artificial creation due to dissection techniques that leave behind thicker fibrous tissues mistakenly classified as a separate UCL.8
On the radial side,
the nomenclature of ligaments is similarly varied,
though not as controversial or discrepant as the ulnar half of the wrist.8,9 Brown identifies the fibers originating from the most radial aspect of the radial styloid,
inserting on the waist of the scaphoid.1 Siegel looked at the origins and dimensions of palmar and dorsal radiocarpal ligaments,
and found the radial collateral ligament (RCL) originating from the palmar tip of the radial styloid process in 28/30 wrists,
and the dorsal tip in 2/30 wrists.
The ligament inserted on the distal pole and waist of the scaphoid and the palmar surface of the trapezium,
extending to the base of the thumb metacarpal in 12/30 wrists.10 Like many authors who found the ulnar collateral to be a part of the TFCC,
Berger et al.
identified the RCL as a subset of the radioscaphocapitate ligament (RSC).
Fibers from the most extreme distal aspect of the radial styloid,
terminating at the radiopalmar surface of the waist of the scaphoid,
form their version of the radial collateral ligament.11
Wrist MRI is technically the most difficult and challenging among musculoskeletal MRIs.
It requires high-resolution,
high signal-to-noise,
high contrast with small field of view imaging for accurate assessment of anatomy and pathology,
because each structure of the wrist is small and thin.
In addition,
MRI of the collateral ligaments of the wrist has rarely been reported partially because of anatomical complexity and less consensus.
Therefore,
the purpose of this study was to identify and classify the morphology of the UCL and RCL of the wrist using high-resolution 2D and isotropic 3D FSE PDWI sequences.