6.2.1 - Patient Positioning The hand and wrist are imaged using a dedicated quadrature, or phased array RF coil to obtain high SNR and spatial resolution images. Either the Medical Advances Quadrature Wrist Coil or MRI Devices Four-channel Phased Array Coil is used for imaging the wrist at our center. The patient's arm may be positioned at their side, in which case, off-center fields of view must be used. A less optimal technique is to image the wrist with the patient lying prone, in the "superman" position, (i.e. with one arm extended over the head), and the wrist placed at the center of the bore. This position has the advantage of placing the wrist in the most homogeneous region of the magnet, thereby providing the best situation for reliable fat suppression. Unfortunately, this position is uncomfortable, and most patients cannot tolerate this position for the length of a typical MR exam secondary to ipsilateral shoulder discomfort. Proper positioning of the wrist in neutral deviation requires alignment of the long axis of the distal radius with the central metacarpal axis. If the wrist is ulnar-deviated, or radial-deviated this may produce a pseudo-instability pattern when examining the capitolunate angle on sagittal images. Oblique prescriptions are required based on the axial localizer if the wrist is not orthogonally oriented to provide coronal images parallel with the intrinsic ligaments and triangular fibrocartilage (TFC). The wrist can also be imaged in the nonpronated and nonsupinated neutral, or "thumbs-up" position with the fingers held in extension. If the wrist is studied in this neutral position, coronal images are obtained by prescribing sagittal slices. In this case, oblique imaging may be required to produce orthogonal images through the plane of the TFC and intrinsic ligaments of the wrist. If the wrist is imaged in this neutral position, it must be appreciated that the distal radioulnar joint must then be evaluated for stability in pronation and supination. These instability patterns are usually most evident when imaging the wrist in the prone or supine positions. The intrinsic ligaments that are most commonly evaluated using MRI include the scapholunate ligament, and the lunotriquetral ligaments. The intrinsic scapholunate complex consists of the dorsal component, proximal component or membranous component which may show perforations as a normal variant, and the volar or palmar component. Biomechanically, the dorsal component of the scapholunate ligament is the most important component. This should be evaluated on dorsal coronal images, as well as axial images to the scapholunate interval. The lunotriquetral ligament is also divided into a dorsal membranous and volar component. The volar component is biomechanically the strongest portion of the lunotriquetral ligament. It is often more difficult to identify the separate components of the lunotriquetral ligament on coronal images, however, this may be done using axial images. The deltoid arcuate ligaments of the wrist may be evaluated on coronal and sagittal images. Usually the ulnar arm of the arcuate ligament is best seen on volar coronal images, although both components of the deltoid ligament can be seen on corresponding sagittal images. The dorsal component of the dorsal intercarpal ligament can be seen on dorsal coronal images, and consists of the triquetroscaphoid fascicle, and triquetrotrapezial fascicle. It is unusual to see disruption of these structures on routine MR studies.

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