Introduction
A Bennett’s fracture is a break at the base of the thumb that often comes with dislocation. This injury typically occurs from a strong impact, such as during fistfights, playing football, accidents, or falls. Symptoms of Bennett’s fracture include swelling, pain, and limited movement of the thumb. Treatment involves realigning the fractured bone and stabilizing it during the healing process.
Anatomy
The base of the thumb features the metacarpal bone and the trapezium bone in the wrist, which meet to form the carpometacarpal (CMC) joint. The ends of these bones are covered with smooth cartilage, allowing them to glide easily during movement. Strong ligaments and muscles stabilize the CMC joint, providing both mobility and support.
The thumb joint is unique, as it can move in all directions. It allows for upward and downward movement, inward and outward motion, and slight rotation, enabling it to touch the fingers (known as opposition). The thumb is used hundreds of times daily, functioning as an anchor to help the fingers grasp objects. It plays a crucial role in gripping tools, holding glasses, and providing stability for precision tasks like counting coins and writing. A tendon called the abductor pollicis longus, attached to the base of the thumb metacarpal, can contribute to joint dislocation in the case of a Bennett’s fracture.
Causes
A Bennett’s fracture occurs when the metacarpal bone of the thumb breaks and dislocates at its base due to significant forces applied to the bent thumb. This injury can happen during various activities, including sports, falls, and accidents.
Symptoms
Individuals with a Bennett’s fracture often experience pain and stiffness in the thumb, along with noticeable swelling. The thumb may feel unstable and challenging to move normally. If poorly treated, this type of fracture can lead to arthritis over time due to improper realignment of the joint at the base of the thumb.
Diagnosis
To diagnose a Bennett’s fracture, a doctor will examine the hand and take X-rays. In some instances, a computed tomography (CT) scan may be necessary to obtain a more detailed image.
Treatment
Small, uncomplicated fractures without displacement of the bone fragments can be treated non-surgically. In these cases, the bones can remain aligned without surgical intervention, often using a splint or cast. A thumb spica cast or splint is typically applied to keep the thumb in the correct position while it heals. For fractures requiring realignment, surgical intervention may be necessary, using pins, screws, or plates for stabilization.
Surgery
Bennett’s fractures can also be treated through open reduction and internal fixation (ORIF), which involves making an incision at the base of the thumb. Surgical hardware, such as screws, pins, or plates, is used to properly align the fracture for healing. After surgery, a thumb spica cast or splint is worn for several weeks, and thumb range-of-motion therapy is introduced when deemed safe by the doctor.
Recovery
Casts are typically worn for four to six weeks. After removal, patients will engage in hand therapy exercises to enhance mobility, flexibility, and strength in the hand. Generally, Bennett’s fractures caused by low-impact forces have more favorable outcomes compared to those resulting from high-impact forces.
