A Bennett’s fracture happens when the bone at the base of the thumb breaks and dislocates itself. It can result from a forceful injury or fall. A Bennett’s fracture will cause the thumb to swell, pain, and immobility. Treatment requires realigning the broken bone and providing stabilization while it heals.
The metacarpal bone at the base of your thumb and the trapezium bone in your wrist come together forming the carpometacarpal, or CMC joint. Cartilage covers the ends of the metacarpal and trapezium. This cartilage allows the bones to glide easily. Ligaments and muscles hold the CMC joint in place while providing a combination of mobility and stability.
Your thumb joint is the only joint that is able to move in all directions. You move your thumbs hundreds of times each day, many times without even realizing it. A tendon that attaches to the base of the thumb metacarpal, the abductor pollicis longus, is responsible for the joint dislocation that occurs with a Bennett’s fracture.
Bennett’s Fracture Causes
A Bennett’s fracture occurs when the metacarpal bone in the thumb breaks and dislocates at the thumb’s base. Forces impacting the bent thumb will cause this injury. Bennett’s fractures can result from any blunt forces placed on the base of the thumb, such as sports, falls and accidents.
Bennett’s Fracture Symptoms
A Bennett’s fracture will cause your thumb to feel painful and stiff. The area around your thumb will swell. Your thumb may be very unstable and difficult to move. Over time, it is common for a poorly treated Bennett’s fracture to develop severe arthritis. This is because the joint at the base of the thumb was never properly realigned.
Bennett’s Fracture Diagnosis
A doctor can diagnose a Bennett’s fracture by examining your hand and taking X-rays for good measure. In some cases, a CT scan may be ordered to provide a more detailed image.
Bennett’s Fracture Treatment
Small uncomplicated fractures, without displacement of the bone fragments, are normally treated non-surgically. This means that the bones are able to be held in the correct alignment without surgically opening the skin. In this case, a splint and or a cast is used. A thumb spica cast or splint is worn to maintain positioning while the fracture heals. Fractures that require realignment are reduced or realigned surgically and stabilized with pins, screws or plates.
Bennett’s Fracture Surgery
A Bennett’s fracture can also be treated with open reduction and internal fixation, or ORIF. This means that an incision will be made at the base of the thumb. Then, surgical hardware, such as screws, pins, or plates are used to align the fracture to allow it to heal. A thumb spica cast or splint is worn for several weeks following surgery. Physical therapy for range of motion of the thumb starts when your doctor determines it is safe to do so.
Bennett’s Fracture Recovery
Casts are usually worn for four to six weeks after a Bennett’s Fracture is diagnosed. Once removed, you will need to participate in hand therapy exercises to increase the mobility, flexibility, and strength in your hand. In general, Bennett’s fractures caused by low impact forces have better outcomes than injuries caused by high forces.