A fracture of the metacarpal bone involves any of the five elongated, tubular bones located in the palm of the hand, between the carpal bones and the phalanges.
Each metacarpal bone comprises a proximal base at the carpal side, a shaft and a head, commonly known as knuckle. The first metacarpal bone of the thumb is the shortest and broadest of them. Metacarpal fractures are very common and comprise 35% of all fractures of the hand. They can occur at the distal heads, on the neck just below the head (more common fractures), along the shaft, and the base of all the metacarpal bones. Depending on the energy applied to the hand, a fracture of the metacarpals may involve injuries to the cartilage, joint capsule, tendons, ligaments, palmar fascia, the dorsal hood as well as causing nerve damage. A fracture to the little finger metacarpal is called Boxer’s fracture as it occurs when punching a hard object with the closed fist. A fracture of the thumb metacarpal is also called skier’s thumb. In case of fractures to the metacarpal head, the knuckle seems to disappear and its movement provokes pain.
The classification and severity of metacarpal fractures depend on their characteristics. They can be stable, non-displaced or minimally displaced, when the bone fragments maintain their anatomical position or displaced when the bone fragments have moved from their original anatomy. They can also be transverse oblique, and spiral depending on the orientation of the bone break, or comminuted when multiple bone fragments are released.
A Bennett's fracture at the thumb base is the most common fracture of the thumb producing an oblique break of the metacarpal. This fracture affects the function of the underlying joint and requires immediate attention (see separate pathology).
Metacarpal fractures occur more frequently in men. They result from axial forces to the hand, crush injuries, a direct blow or torsion energy. The main causes are:
Sports such as hockey and cricket caused by a direct impact of the bat or hard ball onto the hand
Skiing (thumb metacarpal)b
Boxing (little finger metacarpal)
Falls onto fingers/hands in the elderly has almost 50% incidence of all metacarpal fractures
Catching the hand in carpentry machines
The risk factors of metacarpal fractures simply replicate the causes leading to this pathology and are:
Bat sports (hockey,
Ball sports (basketball, volleyball, football, rugby)
Snow sports (skiing, snowboarding)
Manoeuvring of carpentry machineries
Predisposition to fall (elderly age, epilepsy and other medical conditions)
The symptoms arising from metacarpal fractures are:
The medical history discussed with the examiner will focus on the patients’ previous hand injuries and the dynamic causing the current pathology. The clinical examination of the hand aims to determine:
Changes in the anatomy of the affected hand against the healthy hand
Presence of skin lacerations
Tenderness with axial compression of the finger
Tenderness with movement of the wrist or longitudinal compression as occurring in metacarpal
With a suspected metacarpal fracture X-rays are taken under the antero-posterior, lateral, and oblique view to better assess the fracture characteristics. Additionally, a CT scan or MRI may be required in case of complex fractures.
The management of the metacarpal fractures varies in relation to the fracture site and characteristics. In case of stable fracture surgery is not required and treatment with a cast is adequate. Sometimes a closed reduction is necessary to re-align the fractured metacarpal. A cast is used during the first 3-4 weeks and then replaced with a removable splint if stability is sufficient with supported hand movement. Unstable fractures are treated with immobilisation using a cast to maintain the functional position of the hand and facilitate correct bone healing. A 50-70 degree flexion is used especially if the metacarpal head is fractured. Additional conservative treatments include:
Administration of NSAIDs
Physiotherapy whilst the hand is in a cast or brace
Surgery is required in significantly displaced metacarpal fractures, open fractures, complex intraarticular fractures, and fractures with an angulation over 30 degrees. When conservative treatment fails to achieve bone alignment and healing surgery is necessary. The index metacarpal more often does need surgical treatment, as minimal anatomical changes in the finger alignment can alter the function of the entire hand. Different methods are available for metacarpal fracture fixation depending on the fracture characteristics:
Open reduction and internal fixation (ORIF) is performed in displaced fractures by performing a dorsal incision and placement of screws, plates and K-wires.
External fixation is used in unstable fractures. A closed reduction with percutaneous pining using K-wires is also a frequent option.
Complications after a metacarpal fracture include the non-union of the metacarpal bone when a fracture is neglected, when surgery is delayed, or in case of very unstable fractures. This results in bone misalignment and improper finger rotation.
Chronic Regional Pain Syndrome (CRPS) is a soft tissue reaction leading to prolonged pain and other vascular neural changes of the injured hand but it is a rare complication.
With or without surgery, the use of a cast or splint is recommended for 6-12 weeks. The prognosis depends on the severity of the fracture. Any physical activities that involve grasping, gripping, pulling and punching should be avoided until complete fracture healing has been achieved. Once pain has resolved the patient can begin to move the wrist, hand and fingers to prevent stiffness. Intensive physical therapy usually commences approximately 6-8 weeks after surgery. A physical or occupational therapist will plan exercises to restore flexibility and strength of the hand. Education is critical to inform the patient how to modify activities and avoid recurrent injuries to the metacarpals. Additional rehabilitative therapy includes:
Activity modification advice
Return to activity plan
Preventing metacarpal fractures aims at reducing the risk of falls in the elderly and protect the hands during physical activities. Common strategies are:
Use of hand protective gear in sport or carpentry work
Use of devices to improve stability and avoid falls in elderly patients
Modification of physical activities
Exercise to improve muscle strength, flexibility and posture