Bennett fracture  is a type of partial broken finger involving the base of the thumb, and extends into the carpometacarpal (CMC) joint.Treatment typically requires surgery.This intra-articular fracture is the most common type of fracture of the thumb, and is nearly always accompanied by some degree of subluxation or frank dislocation of the carpometacarpal joint. Symptoms and signs
Symptoms of Bennett fracture are instability of the CMC joint of the thumb, accompanied by pain and weakness of the pinch grasp. Characteristic signs include pain, swelling, and ecchymosis around the base of the thumb and thenar eminence, and especially over the CMC joint of the thumb. Physical examination demonstrates instability of the CMC joint of the thumb. The patient will often manifest a weakened ability to grasp objects or perform such tasks as tying shoes and tearing a piece of paper. Other complaints include intense pain experienced upon catching the thumb on an object, such as when reaching into a pants pocket. Complications
Many important activities of daily life are dependent on the ability to grasp, pinch, and oppose the thumb. In fact, thumb function constitutes about 50% of overall hand function. These abilities are in turn dependent on an intact and functional thumb CMC joint.
In such cases, closed reduction followed by immobilization in a thumb spica cast and serial radiography may be all that is required for effective treatment. For Bennett fractures where there is between 1 mm and 3 mm of displacement at the trapeziometacarpal joint, closed reduction and percutaneous pin fixation (CRPP) with Kirschner wires is often sufficient to ensure a satisfactory functional outcome. The wires are not employed to connect the two fracture fragments together, but rather to secure the first or second metacarpal to the trapezium. For Bennett fractures where there is more than 3 mm of displacement at the trapeziometacarpal joint, open reduction and internal fixation (ORIF) is typically recommended.Regardless of which approach is employed (nonsurgical, CRPP, or ORIF), immobilization in a cast or thumb spica splint is required for four to six weeks. Prognosis
If intraarticular trapeziometacarpal fractures (such as the Bennett or Rolando fractures) are allowed to heal in a displaced position, significant post-traumatic osteoarthritis of the base of the thumb is virtually assured. Some form of surgical treatment (typically either a CRPP or an ORIF) is nearly always recommended to ensure a satisfactory outcome for these fractures, if there is significant displacement.The long-term outcome after surgical treatment appears to be similar, whether the CRPP or the ORIF approach is used. Specifically, the overall strength of the affected hand is typically diminished, and post-traumatic osteoarthritis tends to develop in almost all cases. The degree of weakness and the severity of osteoarthritis does however appear to correlate with the quality of reduction of the fracture.