What is a Bennett’s Fracture-Dislocation?

Bennett’s fracture-dislocation is a broken bone (fracture) at the base of the thumb bone (metacarpal), at the wrist. The metacarpal bones connect the wrist to the fingers and make up the arch of the hand. Fracture of the metacarpal to the thumb (first metacarpal) occurs at the wrist and involves the joint between the metacarpal and the wrist bones. A muscle and tendon attach to the shaft (long portion of the metacarpal) causing it to separate (displace) from the smaller bone fragment, keeping the broken bone ends apart.

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How does Bennett’s fracture-dislocation occur?

• Direct blow, such as a striking blow with the fist
• Indirect stress to the hand, such as that caused by twisting or violent muscle contraction (uncommon)

What increases the risk of developing Bennett’s fracture-dislocation?

• Participation in contact sports such as football, rugby or soccer
• Sports that require hitting, such as boxing or martial arts
• History of bone or joint disease, including osteoporosis

What are the symptoms of Bennett’s fracture-dislocation?

• Severe pain at the time of injury
• Pain, tenderness, swelling (especially at the base of the thumb and the back of the hand) and, later, bruising of the hand
• Visible deformity if the fracture is complete and the bone fragments separate enough to distort normal body contours
• Pain, weakness, and inability to grip or hold objects
• Numbness or paralysis from swelling in the hand, causing pressure on the blood vessels or nerves (uncommon)

How is Bennett’s fracture-dislocation diagnosed?

Bennett’s fracture-dislocation is suggested by the history and physical exam. X-ray confirms the diagnosis.

How is it treated?

Non-surgical treatment: If the bones are in acceptable alignment, the initial treatment consists of ice and elevation of the injured hand at or above heart level to reduce swelling, with the addition of medication to relieve pain. Immobilization by splinting, bandaging, casting or bracing for four or more weeks is usually recommended to protect the bones while they heal.

Surgical treatment

Surgery is often necessary because these fractures are unstable. In other words, even if the fragments can be reduced (placed in the correct position), they usually do not remain reduced without something to hold them, such as pins or screws. This is because muscles and tendons attach to one of the fragments, causing it to displace.

For fractures that are displaced (out of alignment), surgery is usually recommended because of the instability and joint misalignment. Surgery usually involves placement of removable pins, screws or plates.