Orthopaedic Surgery - Metacarpal Fracture

Basics

A metacarpal fracture is a break involving one of the five metacarpal bones of the hand, which form the skeletal base of each digital ray.

These fractures are classified according to the anatomic location of the break:

Head

Neck

Shaft

Base

A fracture through the neck of the fifth metacarpal is commonly called a boxer’s fracture because it often results from striking an object with a clenched fist.

Boxer’s Fracture

A boxer’s fracture is usually a fracture through the neck of the fifth metacarpal.

The classic mechanism is:

Axial loading through the fifth metacarpophalangeal joint during a punch.

The fracture typically develops an apex-dorsal angulation.

Thumb Metacarpal Fractures

Fractures involving the base of the thumb metacarpal are commonly divided according to:

Whether the fracture is intra-articular or extra-articular and the degree of comminution.

Several characteristic patterns have eponymous names.

Bennett Fracture

A Bennett fracture is an intra-articular fracture-dislocation of the base of the first metacarpal.

A volar-ulnar fragment remains attached to the carpometacarpal joint, whereas the remainder of the metacarpal base is displaced by deforming muscular forces.

Because of this displacement, Bennett fractures are inherently unstable.

Rolando Fracture

A Rolando fracture is a comminuted intra-articular fracture of the first metacarpal base.

The classic pattern is Y- or T-shaped and involves the thumb carpometacarpal joint.

Rolando fractures generally have a worse prognosis than simple Bennett fractures because of the degree of articular comminution.

Epidemiology

Metacarpal fractures are among the most common injuries of the hand.

They account for approximately 20% of upper-extremity fractures in older epidemiologic studies.

An estimated 264,000 cases per year have historically been reported in the United States.

Age and Sex

These injuries occur most frequently in:

Male patients between approximately 15 and 55 years of age.

Risk Factors

Common risk factors include:

Fighting

Contact sports

Falls

Bicycle injuries

Occupational hand trauma

Etiology

Metacarpal fractures may result from:

Direct trauma

Crush injury

Axial loading through the metacarpal head

Axial loading is a particularly common mechanism.

Sports Injuries

Sport-related trauma can produce:

Neck, shaft, or base fractures, depending on the direction and magnitude of force.

Falls and Bicycle Injuries

A fall onto the hand or direct impact during a bicycle accident can produce metacarpal fractures, sometimes with associated soft-tissue injury.

Diagnosis

Signs and Symptoms

The diagnosis is usually established by combining:

History, physical examination, and plain radiographs.

Patients commonly complain of:

Pain, swelling, bruising, and deformity, most prominently over the dorsum of the hand.

Physical Examination

Inspection

Look for:

Swelling

Ecchymosis

Loss of normal knuckle contour

Angular deformity

Open wounds

Metacarpal Shortening

Shortening may cause an apparently absent or flattened knuckle when the patient makes a fist.

The involved metacarpal head may appear recessed compared with adjacent digits.

Rotational Alignment

Rotation is one of the most important components of the examination.

Assess the finger cascade both:

At rest and during active fist formation.

Normally, the fingers converge toward the scaphoid region without crossing.

Malrotation

Any overlap or scissoring of the fingers suggests rotational deformity.

Unlike some degree of angulation, clinically evident malrotation is not acceptable because it substantially affects hand function.

Neurovascular Examination

Document:

Capillary refill

Digital perfusion

Light-touch sensation

Two-point discrimination

Motor function should also be assessed when possible.

Skin Examination

Any break in the skin must be examined carefully.

The clinician should determine whether the injury represents an open fracture.

Fight Bite Injury

An apparently small laceration over the MCP joint after punching another person may represent a human bite injury involving the joint or metacarpal head.

These injuries are potentially serious because a tooth may penetrate the:

Skin, extensor mechanism, joint capsule, and articular surface.

They require urgent recognition and treatment.

Laboratory Tests

Routine laboratory tests are not required for uncomplicated closed metacarpal fractures.

Laboratory investigations may be appropriate if infection or another systemic issue is suspected.

Imaging

Plain radiographs are the standard initial study.

Obtain:

AP

Lateral

Oblique views

True Lateral View

A true lateral radiograph is particularly important for assessing:

Fracture angulation.

Focused Views

Dedicated views centered on the involved metacarpal may provide better definition of:

Fracture pattern, displacement, comminution, and articular involvement.

Pathological Findings

Acute fracture produces:

Disruption of the cortex and periosteum with hematoma formation.

Healing subsequently progresses through:

Callus formation, consolidation, and remodeling.

Differential Diagnosis

Important alternatives or associated injuries include:

MCP joint dislocation

Extensor tendon injury

Flexor tendon injury

Soft-tissue contusion

Ligament injury

Treatment

General Principles

Most metacarpal fractures can be treated nonoperatively if:

Alignment is acceptable, rotation is normal, the fracture is stable, and there is no important articular displacement.

Treatment commonly consists of:

Reduction when required, splinting or casting, followed by early range-of-motion exercises.

Immobilization

Many uncomplicated fractures are immobilized for approximately 3 weeks, although the exact duration depends on stability, location, and symptoms.

Prolonged immobilization should be avoided because it increases the risk of stiffness.

Intrinsic-Plus Position

When the fingers are included in the splint, the hand is traditionally immobilized in the intrinsic-plus or safe position.

This generally places the:

MCP joints in flexion and the interphalangeal joints relatively extended.

This position helps maintain collateral ligament length and reduces the risk of stiffness.

However, several studies have found little difference in final outcomes among different splinting techniques for many stable fractures.

Initial Symptomatic Care

Initial management should also include:

Ice

Elevation

Analgesia

These measures reduce swelling and discomfort.

Reduction

Closed reduction is performed when angulation, shortening, or displacement exceeds acceptable limits.

The patient should be advised that surgery may become necessary if satisfactory reduction:

Cannot be obtained or cannot be maintained.

Acceptable Angulation: Metacarpal Neck Fractures

Acceptable apex-dorsal angulation increases from the radial to ulnar side because the ring and small-finger CMC joints permit greater compensatory motion.

Reasonable historical guidelines are:

Index metacarpal: approximately 10°

Long metacarpal: approximately 10°

Ring metacarpal: approximately 20–30°

Small-finger metacarpal: approximately 40–70°

Clinical function, fracture stability, shortening, and rotation must also be considered.

Acceptable Angulation: Metacarpal Shaft Fractures

Shaft fractures generally tolerate less deformity than neck fractures.

Approximate historical limits are:

Index metacarpal: essentially no significant angulation

Long metacarpal: essentially no significant angulation

Ring metacarpal: approximately 20°

Small-finger metacarpal: approximately 30°

Rotation

Unlike angular deformity:

No clinically significant rotational deformity should be accepted.

Even a small amount of metacarpal rotation may produce major overlap of the fingertip during flexion.

Intra-Articular Fractures

Fractures involving a joint surface require particularly careful assessment.

Significant:

Articular step-off, displacement, or instability

may require operative reduction.

The goal is to restore joint congruity and reduce the risk of post-traumatic arthritis.

Open Fractures

Open metacarpal fractures require prompt treatment.

Management may include:

Antibiotics

Tetanus prophylaxis when appropriate

Irrigation

Surgical débridement

Fracture stabilization

Fight-Bite Injuries

Human-bite injuries over the MCP joint are treated aggressively because of the high risk of infection.

Treatment commonly includes:

Early antibiotics, surgical irrigation and débridement, and evaluation of the joint, tendon, and bone.

Fracture Healing

Most uncomplicated metacarpal fractures achieve substantial union within approximately 6–8 weeks.

Clinical healing and functional recovery may occur at different rates.

Physical Therapy

Early motion is important.

Finger Range of Motion

Gentle active and passive exercises should begin as soon as fracture stability permits.

For many fractures, finger motion should begin within approximately 3 weeks of injury, and often earlier if fixation is stable.

Wrist Motion

Wrist range of motion should also be restored progressively when immobilization no longer requires restriction.

Goals of Rehabilitation

Therapy aims to restore:

Finger flexion and extension

Wrist motion

Grip strength

Tendon excursion

Fine motor function

Surgery

Operative treatment includes:

Closed reduction with percutaneous fixation

and

Open reduction with internal fixation.

Surgical Goals

The goals are:

Stable reduction

Preservation of length and rotation

Minimal soft-tissue disruption

Early mobilization

Indications for Surgery

Operative treatment is considered for:

Unstable fractures

Multiple metacarpal fractures

Significantly displaced intra-articular fractures

Open fractures

Unacceptable angulation

Metacarpal shortening with functional consequences

Any persistent malrotation

Failure of closed reduction

Loss of reduction during follow-up

Surgical Fixation Options

Fixation methods include:

Percutaneous Kirschner wires

Plate-and-screw fixation

Lag screws

Intramedullary fixation

External fixation

The choice depends on fracture pattern, location, soft-tissue condition, and surgeon preference.

Percutaneous Pinning

K-wire fixation provides relatively minimally invasive stabilization and is commonly used for:

Neck, shaft, and base fractures.

Pins may be placed transversely, intramedullary, or across adjacent metacarpals depending on the injury.

Plate and Screw Fixation

Plate fixation provides rigid stability and is particularly useful when:

Length or rotational stability cannot otherwise be maintained

or

The fracture is comminuted or associated with bone loss.

Because plates require greater soft-tissue exposure, they may have a higher risk of tendon irritation, adhesions, and stiffness than less invasive methods.

Intramedullary Fixation

Intramedullary devices can provide stable fixation of selected:

Metacarpal neck or shaft fractures

while limiting soft-tissue dissection.

External Fixation

External fixation is rarely required but may be useful when there is:

Severe comminution, major bone loss, extensive soft-tissue injury, or an open high-energy fracture.

Thumb Metacarpal Base Fractures

Bennett Fracture

Bennett fractures are often treated surgically because they are inherently unstable.

Nonoperative treatment may be appropriate only when:

Displacement is minimal and joint congruity can be maintained reliably.

Fixation

Percutaneous pinning is a common technique.

Other options include:

Screw fixation or open reduction, depending on fragment size and displacement.

Rolando Fracture

Comminuted intra-articular fractures of the thumb base are more difficult to reconstruct.

Treatment may involve:

K-wires, screws, plates, or external fixation, depending on the number and size of fragments.

Follow-Up

Radiographic Monitoring

Radiographs are commonly obtained approximately 1 week after reduction to confirm maintained alignment.

Repeat imaging may be performed another 2–3 weeks later or according to fracture stability.

Early Motion

Finger motion should begin early, generally within approximately 3 weeks, and often earlier when fixation permits.

The goal is to prevent:

MCP and interphalangeal stiffness and tendon adhesions.

Prognosis

The overall prognosis is good to excellent for most appropriately treated metacarpal fractures.

Stable fractures treated nonoperatively generally heal well with useful hand function.

Percutaneous Fixation Outcomes

K-wire and intramedullary fixation can provide excellent results for:

Metacarpal neck fractures.

K-wire fixation can also produce good outcomes in:

Shaft and base fractures.

Plate Fixation Outcomes

Plate fixation provides strong stability but may have a higher complication burden than nonoperative care or less invasive fixation.

Nevertheless, it can be essential for:

Unstable, comminuted, or bone-loss fractures.

Thumb Base Fracture Prognosis

Bennett fractures generally have good results when:

Articular alignment and CMC stability are restored.

Comminuted Rolando-type fractures have a less favorable prognosis because articular reconstruction is more difficult.

Complications

Soft-Tissue Injury

The original trauma may damage:

Skin, tendons, nerves, and soft tissues.

Repeated aggressive reduction attempts can worsen this injury.

Tendon Dysfunction

Flexor or extensor tendons may develop:

Adhesions, reduced excursion, or mechanical irritation.

Metacarpal shortening can also alter tendon mechanics.

Malunion

Malunion may produce:

Angular deformity, shortening, or rotation.

Rotational malunion is particularly poorly tolerated because it causes digital overlap during grip.

MCP Stiffness

Immobilizing the MCP joint in excessive extension may allow the collateral ligaments to shorten.

This can produce persistent stiffness.

Early motion and appropriate positioning help reduce this risk.

Surgical Complications

Potential complications include:

Infection

Delayed wound healing

Sensory nerve injury

Tendon irritation or adhesions

Hardware prominence

Loss of fixation

Joint stiffness

Patient Monitoring

Follow-up should assess:

Pain, swelling, rotational alignment, fracture stability, neurovascular status, and finger motion.

Radiographs are used to confirm maintenance of reduction and progression of healing.

Key Principle

Successful treatment of metacarpal fractures depends less on eliminating every degree of angulation than on preserving:

Rotation, length, joint congruity, stability, and early finger motion.

In particular, malrotation should not be accepted, because even modest rotational deformity can substantially impair hand function.