The pisiform is a small, pea-shaped bone in the wrist, found on the pinky finger side of the hand. Its name is derived from the Latin word “pisum,” meaning “pea.” The pisiform is the last of the carpal bones to harden during development.
Anatomy and Function of the Pisiform
The pisiform is on the palm side of the wrist, resting on the triquetrum bone. It is a sesamoid bone, meaning it is embedded within a tendon. The pisiform is located inside the tendon of the flexor carpi ulnaris, a muscle that bends the wrist toward the pinky finger.
The pisiform functions like a pulley, increasing the mechanical advantage of the flexor carpi ulnaris tendon. This enhances the force and efficiency of wrist movements. The bone also serves as an attachment point for ligaments and the abductor digiti minimi, a muscle that moves the little finger.
Common Injuries and Conditions
Pain related to the pisiform can stem from its articulation with the triquetrum bone. Pisotriquetral arthritis is a condition where the cartilage between these bones wears down, causing pain and limited mobility. This arthritis can be caused by overuse or direct trauma.
Pisiform fractures are uncommon, accounting for less than 2% of all carpal fractures. They occur from a direct impact, such as falling onto an outstretched hand. Due to their rarity, these fractures can be missed during an initial examination.
The pisiform forms a border of Guyon’s canal, a narrow passageway in the wrist for the ulnar nerve. Injury, swelling, or arthritic changes to the bone can compress this nerve. This compression may lead to numbness, tingling, or weakness in the ring and pinky fingers.
Treatment for Pisiform-Related Pain
Managing pain from pisiform issues begins with conservative methods. The initial approach involves rest, ice, and over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain and swelling.
If symptoms persist, a doctor may recommend immobilizing the wrist with a splint or brace. A short arm cast is a common treatment for non-displaced fractures. Physical therapy is another option to improve wrist mechanics and strengthen surrounding muscles.
For severe cases, a physician might suggest a corticosteroid injection into the pisotriquetral joint to decrease inflammation. When conservative treatments fail, surgery may be considered. The most common surgical procedure is a pisiformectomy, which is the complete removal of the pisiform bone.