Metacarpal fractures
‍Anatomy of the hand showing the metacarpal bones between the wrist carpals and the phalanges

Definition

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.

Pathology

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.

Classification

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).

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

 A blow onto the hand with a hockey bat can cause a metacarpal fracture

Causes

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

Snow sports are a risk factor for matacarpal fractures

Risk factors

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) 

Boxing

Manoeuvring of carpentry machineries

Predisposition to fall (elderly age, epilepsy and other medical conditions)

Severe swelling of the hand is a typical symptom after a matacarpal fracture

Symptoms

The symptoms arising from metacarpal fractures are:

Pain

Swelling

Bruising

Movement restrictions

Hand deformity

Knuckle asymmetry/depression

Palpation and instability tests are used to diagnose an underlying metacarpal fracture

Diagnosis

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

Digit malrotation

Knuckle depression

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. 

Treatment

A cast is often used for conservative treatment of metacarpal fractures

Nonoperative treatment

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:

Rest

Hand elevation

Ice pads

Administration of NSAIDs

Painkillers

Physiotherapy whilst the hand is in a cast or brace

Internal fixation of the 5th metacarpal (left) and external fixation of the thumb metacarpal (right)

Surgical treatment

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

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.

Electrotherapy of the hand dorsum

Rehabilitation

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:

Massage

Joint mobilisation

Stretches

Electrotherapy

Activity modification advice

Return to activity plan

Padded gloves are used in a variety of sports to prevent hand injuries

Prevention

Preventing metacarpal fractures aims at reducing the risk of falls in the elderly and protect the hands during physical activities. Common strategies are:

Postural taping

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