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The hand and wrist are among the most often radiographed areas of the skeleton in any age group. The high frequency of traumatic fractures as well as the painful degenerative conditions from repetitive microtrauma or arthritic deformities account for this. The clinicians involved in treatment of the hand and wrist rely on imaging to assist in accurate diagnosis to minimize delays in providing appropriate treatment—delays that may result in long-term disability and surgery.

Review of Anatomy110

Osseous Anatomy

The 27 bones that make up one hand and wrist are divided into three groups: the phalanges, the metacarpals, and the carpals (Fig. 17-1).

Figure 17-1

Osseous anatomy of the hand, dorsal aspect.

The phalanges are the fingers and thumb, or digits, of the hand. They number 14, with a proximal, middle, and distal phalanx forming each finger and a proximal and distal phalanx forming the thumb. Each phalanx is a miniature long bone characterized by the presence of a base, a shaft, and, most distal, a head. The thumb is designated as the first digit, and the fingers are consecutively numbered as digits 2 through 5.

Five metacarpals form the palm of the hand. They are numbered in the same manner as the digits, with the first metacarpal at the thumb and the fifth metacarpal at the little finger side of the hand. The metacarpals are also miniature long bones, each possessing a base, shaft, and head.

Eight carpals make up the wrist. They are divided into proximal and distal rows for ease of learning their positions. The proximal row from the thumb side consists of the scaphoid, lunate, triquetrum, and pisiform bones. The distal row, from the thumb side, consists of the trapezium, trapezoid, capitate, and hamate bones.

The distal radius has two articular facets separated by a ridge for articulation with the scaphoid and lunate. The sigmoid notch of the distal radius articulates with the distal ulna.

Joints and Ligaments of the Hand and Wrist

Interphalangeal Joints

The interphalangeal (IP) joints are located between the segments of each phalanx (Fig. 17-2). In the fingers they are designated as the distal interphalangeal joints and the proximal interphalangeal joints. The thumb possesses only one interphalangeal joint. Each joint is supported by an articular capsule and palmar (volar) and collateral ligaments. The dorsal aspect is reinforced by expansion of the extensor tendon sheath.

Metacarpophalangeal Joints

The metacarpophalangeal (MCP) joints are located between the bases of ...

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