High-resolution MRI of the ulnar and radial collateral ligaments of the wrist.

Background Accurate diagnosis of injuries to the collateral ligaments of the wrist is technically challenging on MRI. Purpose To investigate usefulness of high-resolution two-dimensional (2D) and isotropic three-dimensional (3D) magnetic resonance imaging (MRI) for identifying and classifying the morphology of the ulnar and radial collateral ligaments (UCL and RCL) of the wrist. Material and Methods Thirty-seven participants were evaluated using 3T coronal 2D and isotropic 3D images by two radiologists independently. The UCL was classified into four types: 1a, narrow attachment to the tip of the ulnar styloid (Tip); 1b, broad attachment to the Tip; 2a, narrow attachment to the medial base of the ulnar styloid (Base); and 2b, broad attachment to the Base. The RCL was also classified into four types: 1a, separate radioscaphoid and scaphotrapezial ligaments (RS + ST) with narrow scaphoid attachment; 1b, RS + ST with broad scaphoid attachment; 2a, continuous radio-scapho-trapezial ligaments (RST) with narrow scaphoid attachment; and 2b, RST with broad scaphoid attachment. The inter-observer reliability of these classifications was calculated. Results Type 1a was the most common of both collateral ligaments. Of UCL classifications, 31.4% were revised after additional review of multiplanar reconstruction (MPR) images from isotropic data. The inter-observer reliability of UCL classification was substantial (k = 0.62) without MPR, and almost perfect (k = 0.84) with MPR. The inter-observer reliability of RCL classification was almost perfect (k = 0.89). Anatomic delineation between the two sequences was not statistically different. Conclusion The UCL and RCL were each identified on high-resolution 2D and isotropic 3D MRI equally well. MPR allows accurate identification of the UCL attachment to the ulnar styloid.