Metacarpal Fracture: Diagnosis and Treatment of Fractures of the Metacarpal Bones in Hand Surgery

The human hand is a marvel of mechanics. The five metacarpal bones lie between the carpal bones and the fingers. A fracture of these bones is referred to as a metacarpal fracture or a metacarpal bone fracture. Each of these bones consists of a base (near the carpal bones), a shaft, and a head (near the fingers).

The most common cause of a fracture is direct impact. A metacarpal fracture is usually caused by falling onto the hand or by punching hard surfaces. The fifth metacarpal bone (little finger) is particularly at risk. A typical fracture involving displacement of the bone head is referred to here as a boxer’s fracture. However, shaft fractures of the other metacarpals are also not uncommon. Depending on the severity of the impact, these can be simple fractures or complex comminuted fractures.

A metacarpal fracture is painful and almost always leads to immediate functional impairment. A metacarpal fracture is suspected when the following symptoms occur after a trauma:

• Swelling: Significant swelling on the back of the hand is almost always present, as the soft tissues react strongly.

• Pain: Pressure on the metacarpal bone or pulling on the finger triggers pain.

• Malposition: The affected finger is often shortened or rotated. When making a fist, the fingers cross over each other (a condition known as “finger scissoring”), which may indicate a metacarpal fracture.

• Mobility: Mobility of the hand is severely restricted; the fist can no longer be closed.

Associated injuries to tendons, nerves, or blood vessels must always be ruled out, as a fracture can be complicated by additional injuries. Open fractures, in which bone fragments pierce the skin or additional injuries to the skin and soft tissues are exposed, are medical emergencies.

Fractures at the base of the first metacarpal bone (thumb) require special attention in hand surgery.

• Bennett fracture: This is a dislocated fracture at the base of the first metacarpal bone involving the joint. Tension from the tendon of the long abductor pollicis longus muscle causes malalignment. Since the articular surface is affected, surgical treatment is almost always necessary.

• Rolando fracture: It resembles the Bennett fracture but is usually a T- or Y-shaped comminuted fracture at the base. Here, too, the prognosis is poorer without precise reconstruction, as there is a risk of osteoarthritis.

The diagnosis is confirmed by clinical examination and imaging techniques. The physician checks blood flow, motor function, and sensation (DMS examination) to rule out damage to a blood vessel or nerve.

X-ray examination is the gold standard. An X-ray taken in two planes shows the location of the fracture (base, shaft, head) and the course of the fracture lines. An X-ray also helps rule out dislocations in the carpal bones. In cases of complex carpal fractures or base fractures, a computed tomography (CT) scan may be necessary.

Experts often refer to metacarpal fractures as “boxer’s fractures” because they are frequently caused by a blow to a hard object @ bilderzwerg /AdobeStock

Not every fracture requires surgery. Whether conservative or surgical treatment is chosen depends on the displacement of the bone fragments. If the fracture is stable and there is no rotational deformity, conservative treatment is sufficient.

In this case, the hand is immobilized in a plaster splint or cast. Immobilization is usually performed in the so-called “Intrinsic-Plus” position to prevent the ligaments from shortening. In most cases, conservative treatment can be performed on an outpatient basis. Regular X-ray follow-ups are important to detect any slippage (secondary dislocation). The splint is usually left in place for 3 to 5 weeks.

If the metacarpal fracture is unstable, open, or involves a joint (as in a Bennett fracture), surgery is necessary. Even with a metacarpal fracture, a misdirected punch often causes severe tilting (boxer’s fracture), which should be surgically corrected if it interferes with grasping.

Surgical treatment is usually performed in a hand surgery department. To ensure the procedure is pain-free, the patient receives general anesthesia or brachial plexus anesthesia (numbing of the brachial plexus).

Common procedures include:

• Kirschner wire osteosynthesis: A wire is drilled into the bone to stabilize the fracture fragment. This is often performed using a minimally invasive (percutaneous) technique under X-ray guidance.

• Plate osteosynthesis: For shaft fractures, mini titanium plates are screwed onto the bone. This provides a stable fixation that allows for early mobilization, so the hand does not need to be immobilized for long.

• Screws: Long spiral fractures can often be fixed using screws alone.

If surgery is performed for a metacarpal fracture, gentle range-of-motion exercises can often be started as early as the day after surgery. This is a major advantage over conservative treatment, as the hand is protected but still moved.

For more information on related injuries, see our articles on finger fractures and wrist fractures.

For non-displaced fractures, it is sufficient to immobilize the hand with a splint @ Katja /AdobeStock

The prognosis for a metacarpal fracture is usually good. Bone healing takes about 6 weeks. However, swelling and limited movement may persist longer. Consistent physical therapy is crucial for restoring mobility to the fingers and palm.

Complications are rare but can occur. These include malunion (healing in a misaligned position), pseudarthrosis (formation of a false joint), or complex regional pain syndrome (CRPS). If a metacarpal fracture is not treated surgically when surgery is necessary, this can lead to permanent problems with grasping.