The hamate is one of the many carpal bones of the hand and wrist. The Hamate bone is a triangular bone located in the distal carpal row situated on the ulnar side of the hand. The Hamate is composed of a body and a hook. The ulnar nerve passes through the Guyon’s canal between the Hamate and Pisiform bones. The ulnar nerve can become injured by a fracture of the body (rare) or by a fracture of the hook (common) which may cause neuropathy of the ulnar nerve within the Guyon’s canal. Missing the fracture can lead to persistent pain from nonunion. Hamate hook fractures are most often seen in racquet, bat, or club sports such as hockey and golf. Fractures of the Hamate bone are difficult to diagnose and routine x-rays may not show the fracture. Hook fractures of the Hamate are best seen by carpal tunnel x-ray views; however, a CT scan is the best study. The physician should rule out the ossification center (os hamuli proprium).
During the clinical evaluation, the physician should observe for hypothenar pain, as well as pain and paresthesia of the ring and small finger due to ulnar nerve compression in the Guyon’s canal. There may be weakness of intrinsics and a decrease in grip strength. The most common findings are pain and tenderness on the ulnar side of the wrists, distal to the wrist joint. The pull test is recently described. During the pull test, the palm of the hand is placed into supination. The wrist is in full ulnar deviation. Fingers of the patient should be flexed. The examiner pulls on the ulnar two digits with the patient resisting the pull. A positive test with pain in the area of the hook indicates a fractured hook of Hamate injury. Differential diagnosis include a pisiform fracture. When the physician is checking the Hamate hook for a fracture, if the ulnar side hook is normal, they should then check the pisiform bone. A CT scan may be necessary.
Treatment for acute fractures include early immobilization for 4-6 weeks to avoid nonunion. For a symptomatic nonunion of the hook of Hamate, there will need to be an excision of the fracture fragment. An ORIF is rare.