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INTRODUCTION

A large number of diagnoses are possible when a patient presents with pain in the hand, wrist, or elbow. However, a clinician can often reduce the broad differential diagnosis to either one most likely possibility or a small number of potential considerations by taking a systematic approach to history and examination. When etiology, anatomic location, and epidemiology are cross-referenced relative to one another, the number of possible diagnoses narrows substantially.

We begin this chapter with a review of the hand and wrist anatomy.

Hand & Wrist Anatomy

A. Bones and Joints

  • Two forearm bones, the radius and ulna, which articulate at the distal radioulnar joint. These bones permit forearm rotation (pronation and supination).

  • Eight carpal bones arranged into two rows, referred to as the “proximal row” (scaphoid, lunate, triquetrum, pisiform) and the “distal row” (trapezium, trapezoid, capitate, hamate).

  • Five metacarpal bones, one for the thumb and each of the other digits.

  • The thumb has two phalanges; each of the remaining digits has three phalanges.

  • The joints between the carpal bones and metacarpal bones are known as carpometacarpal (CMC) joints.

  • The joints between the metacarpal and the proximal phalanges are known as metacarpophalangeal (MCP) joints.

  • The joints between the phalanges make up the proximal and distal interphalangeal (PIP and DIP) joints.

B. Extrinsic Digital Extensors

  • Extension of the digits is controlled by muscles in the dorsal forearm, which terminate as tendons that insert terminally on the dorsal aspect of the distal phalanges.

  • The extensor digitorum communis (EDC), the main digital extensor, gives off a tendon to each digit except the thumb.

  • The index and small fingers each have their own extensor in addition (extensor indicis proprius and extensor digiti quinti, respectively). These muscles provide independent extension of those two digits.

  • The thumb has its own extensor, extensor pollicis longus (EPL).

  • The sagittal bands, an expansion of connective tissue over the MCP joints, keep the extensor tendon centralized over the MCP joint. Rupture, typically of the radial-sided sagittal band, causes extensor tendon dislocation in an ulnar direction, eventually leading to ulnar drift of the digits.

C. Extrinsic Digital Flexors & Pulley System

  • Digital flexion is controlled by muscles in the volar forearm. These muscles terminate as tendons that insert on the middle and distal phalanges.

  • Each nonthumb digit has two flexor tendons. The flexor digitorum superficialis (FDS) flexes at the PIP joint and the flexor digitorum profundus (FDP) flexes the digits at the DIP joint. To test tendon integrity, motion across the PIP and DIP joints must be tested separately.

  • The thumb has its own flexor, the flexor pollicis longus (FPL).

  • The flexor tendons are constrained against the bone by bands of connective tissue called pulleys. These maximize tendon excursion. Rupture of a pulley may result in bowstringing: The tendon moves ...

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