• Fracture of the neck of the fifth metacarpal.
• Most common metacarpal fracture.
• Usually occurs after striking a hard object with a clenched fist.

Mechanism of Injury

Mechanism

• Direct axial load through a clenched fist.
• Commonly occurs after punching a wall or another person.
• Force is transmitted through the fifth metacarpal, causing fracture at its neck.

Pathoanatomy

Fracture pattern

• Fracture usually occurs at the neck of the fifth metacarpal.
• Distal fragment angulates dorsally.
• Metacarpal head displaces palmarly.
• May produce loss of knuckle prominence and pseudo clawing.

Clinical Features

Symptoms

• Pain over the fifth metacarpal.
• Swelling.
• Deformity over the small finger knuckle.
• Tenderness at the fracture site.

Signs

• Dorsal bump.
• Loss of normal knuckle contour.
• Assess carefully for rotational deformity.

Imaging

Radiographs

• Obtain AP, oblique, and true lateral views.
• True lateral view is essential to assess angulation.

Metacarpal neck angle

• Normal neck angle is approximately 15°.
• Actual deformity = Measured angulation ? 15°.

Carpometacarpal (CMC) Joint Mobility

Second and third CMC joints

• Relatively immobile.
• Deformity is poorly tolerated.

Fourth CMC joint

• Approximately 10 to 15° of compensatory motion.

Fifth CMC joint

• Approximately 20 to 30° of compensatory motion.
• Allows greater acceptance of angulation.

Acceptable Angulation

Fifth metacarpal shaft fracture

• Less than 40° is generally acceptable.

Fifth metacarpal neck fracture

• Less than 50 to 60° of angulation is generally acceptable.

Practical recommendation

• Angulation greater than 50° may require reduction to avoid pseudo clawing.

Treatment

Conservative treatment

• Most fractures are managed nonoperatively.
• Ulnar gutter splint is commonly used.
• Immobilize the hand in the intrinsic plus position.
• Wrist in extension.
• MCP joints flexed.
• Close reduction may be performed if necessary.

Rotational deformity

• Always requires correction.
• Even minimal rotational deformity is poorly tolerated.

Surgical Treatment

Indications

• Significant rotational deformity.
• Unacceptable angulation.
• Unstable fractures.
• Open fractures.

Techniques

• Percutaneous K wire fixation.
• Intramedullary K wire fixation.
• Cross pinning from the fifth to the fourth metacarpal.

Prognosis

Outcome

• Functional outcome is usually excellent.
• Residual dorsal bump is common but rarely affects function.
• Angulation up to 50 to 60° often has satisfactory results.

Recent Evidence

Management

• Studies have shown similar outcomes with buddy taping and splinting for many uncomplicated fractures.
• Pain, grip strength, range of motion, and patient satisfaction are comparable.
• Routine repeated radiographs and prolonged follow up may not always be necessary in uncomplicated cases.

Exam Pearls

Boxer’s fracture

• Fracture of the neck of the fifth metacarpal.

Mechanism

• Punching a hard object with a clenched fist.

Most important deformity

• Rotational deformity must always be corrected.

Acceptable angulation

• Fifth metacarpal neck: up to 50 to 60°.
• Fifth metacarpal shaft: up to 40°.

Immobilization

• Ulnar gutter splint.
• Wrist extended.
• MCP joints flexed.

Reason fifth metacarpal tolerates greater angulation

• Increased mobility of the fifth carpometacarpal joint.