INTRODUCTION

Upper extremity fractures are among the most common of the extremity injuries with carpal fractures accounting for 18 percent of hand fractures and 6 percent of all fractures [1,2]. Of these, fractures to bones of the proximal row are most frequent. Fractures of the pisiform bone occur less often than fractures of the scaphoid, lunate, or triquetrum. Pisiform fractures account for 1 to 3 percent of all carpal bone osseous injuries [3,4].

This topic reviews fractures of the pisiform in adults. An overview of carpal fractures in adults is presented separately. (See "Overview of carpal fractures".)

PERTINENT ANATOMY

The pisiform is a sesamoid bone within the flexor carpi ulnaris tendon (diagnostic image 1). It is easily palpable on the volar surface of the wrist directly proximal to the 5th phalanx at the distal wrist crease. There are ligamentous attachments to the triquetrum, hamate and 5th metacarpal.

MECHANISM OF INJURY

Most commonly the pisiform is injured in a fall on the outstretched hand with the wrist in extension or if the heel of the hand is used like a hammer. When the wrist is in this position, the flexor carpi ulnaris tendon compresses the pisiform to the triquetrum. These mechanisms can create an avulsion fracture of the distal aspect of the pisiform, a linear fracture, or a chondral injury to its dorsal surface. Being an anchor for several ligamentous attachments, and the origin of the abductor digiti minimi, there is a 50 percent chance of an associated injury to the distal radius or to another carpal bone when a fracture of the pisiform is identified [3].

SYMPTOMS AND EXAMINATION FINDINGS

Patients present with pain and swelling at the palmar, and ulnar, aspects of the wrist. There is pain to palpation of the pisiform and over the hypothenar eminence.