Normal and Variant Anatomy of the Wrist and Hand on MR Imaging Joel M. Stein, MD, PhD*, Tessa S. Cook, MD, PhD, Stephanie Simonson, MD, Woojin Kim, MD Magnetic resonance (MR) imaging is the optimal modality for characterizing the ligaments, tendons, muscles, and neurovascular structures of the wrist and hand. Continued refinement in pulse se- quence and coil design permits high-resolution examination of the many small structures and complex anatomy of this region. In this context, frequent anatomic variants and common false positives such as normal areas of high signal inten- sity in ligaments and tendons must be recognized to avoid misdiagnosis and improper treatment. In this article the authors discuss the osseous and soft tissue anatomy of the wrist and hand, as well as normal variants. PROTOCOLS The hand and wrist are best imaged using a dedi- cated phased-array coil to obtain high-resolution images while achieving optimal signal-to-noise ratio (Tables 1 and 2). High-field strength 3-Tesla magnets may be used to generate high-quality images, which can enhance evaluation of the liga- ments and cartilage as well as the triangular fibro- cartilage. Three imaging planes are obtained: axial, coronal, and sagittal. Axial images of the wrist should cover from the distal radius and ulna to the proximal metacarpals with the plane of imaging paralleling the distal radius. The wrist should be in neutral position during imaging. Imaging of the thumb and fingers requires special attention to how the planes of imaging are prescribed. For the thumb, the axial images should be perpendicular to the midshaft of the proximal phalanx. Coronal images can be obtained perpendicular to the line that bisects the sesamoid bones with the sagittal imaging plane perpendicular to the coronal imaging plane. For an individual finger, axial images are ob- tained along the extent of the digit as prescribed by a best-fit line drawn through its center. OSSEOUS STRUCTURES Whereas the ulna forms the dominant articulation at the elbow, the radius is the larger bone at the wrist and provides the largest articular surface. On axial images, the distal radius forms a broad rectangle. The adjacent radial head has the shape of a circle in cross section and articulates with a slight concavity in the medial border of the radius, the sigmoid notch. On coronal images, the margins of the radial metaphysis, physis, and epiphysis are well demonstrated. The radial epiph- ysis is larger at the lateral aspect, where it termi- nates at the radial styloid process, and as a result it has a roughly triangular shape when viewed in the coronal plane. The slightly concave distal articular surface is angled medially and in This work was not supported by any funding agency. The authors have nothing to disclose. Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, 1 Silverstein, Philadelphia, PA 19104, USA * Corresponding author. E-mail address: joel.stein@uphs.upenn.edu KEYWORDS  Normal wrist and hand anatomy  Wrist and hand magnetic resonance imaging  Normal variants Magn Reson Imaging Clin N Am 19 (2011) 595–608 doi:10.1016/j.mric.2011.05.007 1064-9689/11/$ – see front matter Ó 2011 Elsevier Inc. All rights reserved. mri.theclinics.com