Fractures of the hamate bone are rare, difficult to diagnose, and routine x-rays may not show the fracture. Hamate fractures are classified as either a hook fracture or as a body fracture.
Hamate hook fractures are usually seen in individuals who participate in sports which involve a racquet, baseball bat, or from swinging a golf club.
Swinging of the golf club may cause a hook fracture of the Hamate bone. Missing the fracture can lead to persistent pain from nonunion.
Hamate body fractures are associated with axial force trauma, such as a fist striking a hard object, a fall, or from crushing injuries. It may also be accompanied by 4th and 5th metacarpal subluxation. Coronal fractures are the most common type of Hamate body fractures.
There are three types of coronal fractures; Type A (large piece), Type B (moderate piece) and Type C (avulsion). Make sure to watch out for subluxation of the joint due to pull from the Extensor Carpi Ulnaris.
Hook fractures of the Hamate are best seen by carpal tunnel or supination x-ray views. For hamate fractures, CT scan is the best study. A 30° pronated view is helpful for body fractures.
Clinical Evaluation
Pain will be present, especially with axial loading of the ring and little finger or by grasping an object. The patient will have dismissed grip strength. They may have ulnar and median nerve neuropathy symptoms. The most common findings are pain and tenderness on the ulnar side of the wrist, distal to the wrist joint.
The pull test has been recently described. This is when the palm of the hand is placed into supination, the wrist is in full ulnar deviation, and the 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 fractures hook of hamate injury. Pain may also be felt due to compression of the ulnar nerve in the Guyon Canal.
Treatment
Early immobilization for acute fractures with short arm splint for 6 weeks will be used to avoid a nonunion. For symptomatic nonunion, excision of the fracture fragment will be needed.
Types A and B require open reduction and internal fixation, in addition to stabilization of the joint if needed. Type C requires closed reduction and percutaneous pinning of the fragment for stabilization of the joint. If a closed reduction of the joint is not adequate, open reduction and stabilization of the joint should be done. A displaced fragment with subluxation requires reduction of the joint and stabilization of the joint with K-wires or fixation of the fragment.
When a 4th or 5th carpometacarpal dislocation occurs, one should make special effort to find a coronal fracture of the hamate.
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