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], with an estimated incidence from 1 in 100 to 1 in 460 of all carpal fractures .
This topic reviews fractures of the pisiform in adults. An overview of carpal fractures in adults is presented separately. (See "Overview of carpal fractures".)
The pisiform is a sesamoid bone within the flexor carpi ulnaris tendon (image 1). Ossification occurs between 7 and 10 years of age, and is complete by age 12. It is the last carpus to completely ossify. Segmentation may be present before age 12 and should not be confused with fracture . It is easily palpable on the volar surface of the wrist directly proximal to the fifth phalanx at the distal wrist crease. There are ligamentous attachments to the triquetrum, hamate and fifth metacarpal. The pisiform marks the ulnar border of Guyon’s canal. With pisiform fracture there can be concomitant injury to the ulnar nerve, which traverses the canal.
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 to strike an object. 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. The pisiform serves as an anchor for several ligamentous attachments, and is the origin of the abductor digiti minimi, and thus 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 .
SYMPTOMS AND EXAMINATION FINDINGS
Patients present with pain and swelling at the palmar and ulnar aspects of the wrist. Tenderness is present directly over the pisiform and over the hypothenar eminence. Typically, there is no loss of motion in the wrist and no deformity is seen.