Miscellaneous Magnetic Resonance Imaging

There are several additional areas in which magnetic resonance (MR) imaging is useful but should be covered in detail in texts devoted to musculoskeletal (MSK) MRI. They will be only superficially mentioned here. Included in this group are MR of the wrist, hip, elbow, and bone marrow.

Wrist

MR imaging of the wrist has been slower to develop than that of other joints. Similarly, wrist arthrography has not enjoyed the same popularity as that of the knee or shoulder. Nevertheless, MR imaging of the wrist has some definite utility. It is useful in evaluating the carpal bones for fractures and avascular necrosis (AVN). It seems to have some use for evaluating the triangular fibrocartilage (TFC) and the intercarpal ligaments.

Imaging Techniques

Thin-section (2 to 3 mm) T1- and T2-weighted images in both an axial and a coronal plane are usually employed with a dedicated wrist coil or a small surface coil. Some recommend sagittal images as well. A small field of view (FOV) (5 to 8 cm) should be used for maximal resolution. Three-dimensional volumetric coronal images with thin (1 to 2 mm) slices are used in many centers to replace the T2-weighted images. These are especially useful for examining the TFC and the intercarpal ligaments.

Pathology

Triangular Fibrocartilage

The TFC lies between the distal ulna and the carpal bones and is thought to have some shock-absorbing function. It can tear or become detached and cause significant wrist pain and dysfunction. Tears of the TFC can be diagnosed with arthrography or with MR imaging, although it is somewhat controversial as to the significance of a torn TFC. That is because torn TFCs (and torn intercarpal ligaments, for that matter) are found with a high frequency in older patients who do not have wrist pain or dysfunction. Nevertheless, in a young patient with a painful, torn TFC, most hand surgeons would surgically intervene if conservative care was ineffective. For this reason, imaging may play a role.

The normal TFC is predominantly low signal on all imaging sequences and seen to be triangular in shape with the base attaching to the ulna and the apex attaching onto the radius ( Fig. 13.1 ). A detached or torn TFC is best seen in the coronal plane with T2 or gradient-echo sequences and is usually accompanied by joint fluid in both the distal radioulnar and the proximal carpal joints ( Fig. 13.2 ).