Orthopaedic Surgery - Boxer’s Fracture

Basics

A boxer’s fracture refers to a fracture through the neck of the ring or small-finger metacarpal, typically with volar angulation or displacement of the metacarpal head.

It is one of the most frequently encountered hand injuries in the emergency department and usually occurs after striking a hard object, such as a wall or another person, with a closed fist.

When the injury occurs during a physical altercation, the patient should also be evaluated for other traumatic injuries.

Metacarpal Angulation

Some degree of metacarpal neck angulation is normal.

For example, normal metacarpal neck angulation may be approximately 15°, whereas a boxer’s fracture may demonstrate substantially greater volar angulation.

Marked angulation may result in loss of the normal prominence of the knuckle.

Jewelry Removal

All rings and other jewelry should ideally be removed from the injured hand before significant swelling develops and before radiographs are obtained.

If a ring is present on the injured digit and removal is too painful, a digital block or hematoma block may be considered before attempting removal.

Epidemiology

Boxer’s fractures are among the most common hand injuries evaluated in emergency departments.

They occur considerably more often in males than females, with an incidence approximately five times higher in males.

The highest incidence is seen in males aged 10–19 years, followed by males aged 20–29 years.

Incidence

Metacarpal neck fractures of this type account for approximately 10% of all hand fractures.

Risk Factors

Important risk factors include physical altercations, punching a hard surface with a closed fist, recurrent fighting behavior, boxing, and mixed martial arts.

Activities that repeatedly expose the MCP region to direct impact increase the likelihood of injury.

Etiology

The typical mechanism is a direct axial or dorsal force transmitted through the knuckle of a clenched fist.

The fracture usually develops through the metacarpal neck.

The pull of the interosseous muscles contributes to the characteristic apex-dorsal fracture angulation, which corresponds clinically to volar displacement of the metacarpal head.

Effect of Soft-Tissue Forces

The interosseous muscles and surrounding soft tissues influence the position of the fracture fragments.

Shortening of the collateral ligaments may also contribute to an MCP joint flexion posture.

These deforming forces explain why metacarpal neck fractures commonly angulate after injury.

Associated Neurovascular Injury

In severely displaced fractures, the digital neurovascular bundles located on either side of the metacarpal head may be injured.

Neurovascular status should therefore be carefully documented in all significantly displaced injuries.

Fight-Bite Injury

A particularly important associated injury is a fight bite, which occurs when the dorsum of the MCP joint contacts another person’s tooth.

The tooth can create a small laceration that penetrates deeply into the extensor mechanism or MCP joint.

Such injuries require urgent recognition because they can lead to serious infection, including septic arthritis.

Importance of Injury History

Patients injured during a fight may be reluctant to disclose the exact mechanism.

A small wound over the MCP joint should therefore raise concern for a possible human bite even when the initial history is unclear.

Extensor Mechanism Injury

When substantial angulation or displacement is present, the overlying extensor mechanism may also be damaged.

Extensor tendon injury should be considered when there is weakness, abnormal tendon tracking, or difficulty extending the affected finger.

Diagnosis

Signs and Symptoms

Patients typically present with pain and tenderness over the involved metacarpal head or neck.

Swelling and bruising may be present.

The normal knuckle prominence may appear flattened or depressed compared with the opposite hand.

Physical Examination

The dorsal skin should be examined carefully for puncture wounds, abrasions, lacerations, or evidence of an open fracture.

This is particularly important when the injury followed punching another person.

A small dorsal wound should not be assumed to be superficial.

Assessment of Rotational Alignment

Rotational deformity is clinically more important than modest angular deformity.

Rotation is best assessed by flexing the MCP and PIP joints while keeping the DIP joint extended.

The fingers should point toward a common area near the scaphoid tubercle without crossing or overlapping.

Finger Cascade

When the patient flexes the fingers, the digits should form a smooth and symmetric cascade.

Scissoring or overlap of one finger over another suggests malrotation and is an indication for specialist assessment and often operative treatment.

Knuckle Depression

With sufficient volar displacement of the metacarpal head, the normal dorsal prominence of the affected knuckle becomes less visible.

Some residual loss of knuckle contour may remain even after successful healing.

Imaging

Plain Radiographs

Standard radiographic evaluation includes posteroanterior, lateral, and oblique views of the hand.

These views define the fracture location, degree of displacement, angulation, comminution, and possible associated injury.

Measuring Angulation

The degree of volar angulation is most accurately assessed on the lateral radiograph.

The amount of angulation helps guide decisions regarding observation, reduction, or surgery.

MRI

MRI is not routinely required for an uncomplicated boxer’s fracture.

It may be considered if there is concern for significant injury to the extensor mechanism or neurovascular structures that cannot be adequately assessed clinically.

Differential Diagnosis

Conditions that may resemble or accompany a boxer’s fracture include MCP joint dislocation, extensor mechanism injury, fracture of the base of the proximal phalanx, transverse metacarpal shaft fracture, and articular fracture of the metacarpal head.

Careful examination and appropriate radiographs help distinguish these injuries.

Treatment

Open Fracture or Fight Bite

Any associated open fracture or fight-bite injury should be treated as a potentially contaminated wound.

These injuries require intravenous antibiotics and urgent surgical irrigation and debridement.

Failure to recognize a penetrating human bite may lead to deep infection or septic arthritis.

Indications for Hand-Surgery Referral

Referral to a hand surgeon is appropriate when there is malrotation, severe comminution, major angulation, open injury, tendon injury, neurovascular compromise, or significant uncertainty regarding stability.

Nonoperative Treatment

Closed fractures without malrotation can often be treated nonoperatively.

For the ring finger, fractures with less than approximately 30° of volar angulation may often be accepted.

For the small finger, up to approximately 40° of volar angulation may be acceptable in selected patients.

Ulnar Gutter Splint

Stable fractures within acceptable alignment can be immobilized in an ulnar gutter splint or cast.

The hand is generally positioned in the intrinsic-plus position, with MCP flexion and appropriate positioning of the interphalangeal joints.

This helps maintain alignment and reduce stiffness.

Buddy Taping

The injured digit may also be buddy-taped to the adjacent finger beneath the splint or cast.

This helps control rotational alignment during healing.

Indications for Closed Reduction

Closed reduction is considered when volar angulation exceeds acceptable limits.

Reduction may also be required when deformity significantly affects function or finger alignment.

Analgesia for Reduction

Reduction can be performed after appropriate local anesthesia, such as a hematoma block or ulnar nerve block.

Children, highly anxious patients, or patients unable to tolerate manipulation may require procedural sedation.

Jahss Reduction Maneuver

A commonly used reduction technique is the Jahss maneuver.

The MCP and PIP joints of the injured finger are flexed to approximately 90°.

A dorsally directed force is then applied along the proximal phalanx while counterpressure is placed over the metacarpal shaft to correct the angulation.

Contemporary Nonoperative Approaches

More recent evidence suggests that, in many uncomplicated boxer’s fractures without malrotation, formal reduction and rigid casting may not provide superior outcomes compared with functional treatment using a soft wrap or less restrictive support.

Treatment should therefore be individualized according to fracture alignment, stability, symptoms, and patient demands.

Physical Therapy

After approximately 4–6 weeks of immobilization, hand therapy may be started when clinically appropriate.

Both active and passive range-of-motion exercises can be used to restore movement at the MCP and PIP joints.

The goal is to prevent stiffness and regain grip function.

Medication

Pain is usually managed with a combination of acetaminophen and NSAIDs, provided there are no contraindications.

A hematoma block may also be used during acute fracture manipulation in the emergency department or clinic.

Surgical Management

Surgery may be required for significant malrotation, severe comminution, unacceptable angulation, open fractures, or unstable injuries.

Some patients may also request correction of a marked cosmetic loss of knuckle contour, although cosmetic concerns alone should be weighed against operative risks.

Fixation Methods

Operative fixation can be achieved using various combinations of Kirschner wires, screws, or other internal fixation techniques.

Stable fixation may allow earlier controlled motion and reduce the risk of stiffness.

Follow-Up

Most boxer’s fractures heal uneventfully.

Clinical and radiographic follow-up is used to confirm maintenance of alignment and progression toward union.

Prognosis

The prognosis is generally very good.

Most patients experience only temporary loss of motion and hand function.

A mild residual depression of the affected knuckle is common and usually has little effect on hand performance.

Healing Time

Clinical healing usually occurs within approximately 6 weeks.

Strength and full motion may continue to improve after fracture union.

Delayed Presentation

Delayed presentation is relatively common because some patients underestimate the injury or are reluctant to explain the circumstances.

If the fracture is already healing and there is no significant malrotation, functional deficit, or unacceptable deformity, nonoperative treatment may still be appropriate.

Complications

Potential complications include loss of reduction, infection in an open fracture, stiffness, extensor tendon injury, and injury to the digital neurovascular bundles.

Patients undergoing surgical fixation may occasionally require later hardware removal.

Loss of Reduction

Fracture alignment may change during the early healing period.

This is one reason that follow-up examination and radiographs are important, particularly when the initial fracture was substantially displaced.

Infection

Infection is primarily a concern in open fractures and fight-bite injuries.

Deep infection can involve the tendon, MCP joint, or bone and may result in significant long-term hand dysfunction if treatment is delayed.

Patient Monitoring

Repeat radiographs are commonly obtained approximately 1 week after injury to confirm maintenance of alignment.

Further radiographs may be obtained at roughly 2-week intervals until clinical healing, depending on the stability and treatment method.

Clinical monitoring should also assess rotation, motion, tenderness, skin condition, and neurovascular status.

Boxer’s Knuckle

A boxer’s knuckle should not be confused with a boxer’s fracture.

Boxer’s knuckle refers to rupture of the sagittal band over the MCP joint, leading to instability or subluxation of the extensor tendon.

The tendon may displace radially or ulnarly during finger motion.

Clinical Features of Boxer’s Knuckle

Patients may describe painful snapping or popping of the extensor tendon over the knuckle during active or passive motion.

Pain is often reproduced when attempting to extend the MCP joint against resistance while the interphalangeal joints are held extended.

Imaging of Boxer’s Knuckle

Because sagittal band injuries do not usually produce abnormalities on plain radiographs, MRI may be required to confirm the diagnosis and define associated soft-tissue injury.

Management of Boxer’s Knuckle

Suspected sagittal band rupture should be referred to a hand surgeon.

Some injuries can be managed with appropriate splinting, whereas others require operative repair, particularly when extensor tendon instability is persistent or severe.