Chapter 16

### INTRODUCTION

In recent years, magnetic resonance imaging (MRI) has become a very important modality for diagnosing wrist and hand diseases including osteoarthritis, rheumatoid arthritis (RA), occult fracture, avascular necrosis (AVN), ligamentous/tendinous injuries, impaction syndrome, and nerve entrapment syndrome.1,2 MRI is a noninvasive and nonirradiative imaging tool, and can provide high soft tissue contrast resolution. Thin and contiguous slices are needed for adequate MR imaging of the wrist because even the larger ligaments of the wrist are no greater than 1–2 mm thick.3 New MRI techniques such as 3D volume acquisitions on higher magnetic fields improve signal to noise ratios and visualization of wrist structures in detail with a shorter scan time.4

### ANATOMY

The distal radius and ulna articulate with the proximal row of the carpal bones consisting of the scaphoid, lunate, and triquetrum. The pisiform, a sesamoid bone, is also found in the proximal carpal row and articulates only with the triquetrum. The distal carpal row contains the trapezium, trapezoid, capitate, and hamate, which are articulating with the base of the metacarpal bones and carpal bones of the proximal row (Figure 16-1). The combination of intrinsic and extrinsic ligaments is stabilizing the wrist. Intrinsic wrist ligaments are entirely within the carpus. Extrinsic wrist ligaments have an attachment on the carpus and pass out of the carpus. The strongest ligaments of the wrist are volar extrinsic ligaments, then intrinsic ligaments including the scapholunate (SL) and lunotriquetral (LT) ligaments and the weakest are dorsal extrinsic ligaments. Among these ligaments, the SL and LT ligaments are more important in daily practice since these ligaments are vulnerable to attritional wear. The SL ligament has U shape and the LT ligament has V shape in sagittal plane (Figure 16-2).57

###### Figure 16-1.

Wrist anatomy. (A) Schematic drawing and (B) coronal proton density MR image of the wrist show anatomy of carpal bones. U = Ulna, R = Radius, S = Scaphoid, L = Lunate, Tq = Triquetrum, T = Trapezoid, C = Capitate, H = Hamate, MC = Metacarpal bones.

###### Figure 16-2.

Wrist anatomy. (A) Schematic diagram shows triangular fibrocartilage complex (TFCC), scapholunate (SL), and lunotriquetral (LT) ligaments. (B) Coronal proton density with fat saturation MR image of the wrist shows TFCC (long arrow), LT ligament (short arrow) and SL ligament (Circle). U = Ulna, R = Radius, S = scaphoid, L = Lunate, Tq = Triquetrum, C = Capitate.

The triangular fibrocartilage complex (TFCC) is located between the ulnar head and the first carpal row (the lunate and the triquetrum). The TFCC has three main roles: (1) stability of the distal radioulnar joint (DRUJ), (2) axial load transmission ...

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