Metacarpal Fractures / Hand metacarpal fractures

1. General Overview & Epidemiology & Etiology

Metacarpal fractures represent approximately 30% to 40% of all hand fractures.

• Most Common Site: The fifth metacarpal (often referred to as a "Boxer's fracture") is the most frequently injured bone in this group.

• Demographics: These injuries are most prevalent in young men, typically occurring during the second and third decades of life.

• Mechanism: Common causes include direct impact (punches), falls, or crush injuries.

• Anatomic location: Metacarpal neck is most common site of fracture, fifth metacarpal is most commonly injured.

Etiology

Mechanism of injury direct blow to hand or rotational injury with axial load high energy injuries (ie. automobile) may result in multiple fractures

Open fractures or concomitant soft tissue injury ,tendon laceration, neurovascular injury, compartment syndrome

2. Relevant Anatomy

The metacarpals are five long bones that form the framework of the palm.

• Structure: Each metacarpal consists of a base (proximal), a shaft, a neck, and a head (distal). Concave on palmar surface

• Stability: The second and third metacarpals are relatively fixed at the base, providing a stable central pillar for the hand. The fourth and fifth metacarpals are more mobile at the carpometacarpal (CMC) joint.

• Deforming Forces: The interossei and lumbrical muscles exert forces that typically cause apex-dorsal angulation in metacarpal shaft and neck fractures.Three palmar and four dorsal interossei muscles arise from metacarpal shafts

Tendons

·       extensor carpi radialis longus/brevis

insert on the base of metacarpal II, III (respectively); assist with wrist extension  radial flexion of the wrist

·      extensor carpi ulnaris   

 inserts on the base of metacarpal V; extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist 

·      abductor pollicis longus

inserts on the trapezium and base of metacarpal I; abducts thumb in frontal plane; extends thumb at carpometacarpal joint

·      opponens pollicis

inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips

·       opponens digiti minimi

inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.

3. Clinical Presentation & Physical Examination

Clinical Complaints:

• Pain, swelling, and bruising over the dorsum of the hand.

• Loss of knuckle prominence.

• Weakness in grip strength.

Physical Examination Findings:

• Rotational Deformity: The most critical clinical finding. Fingers should point toward the scaphoid tubercle when flexed; any "scissoring" indicates a rotational malalignment.

• Shortening: Measured by comparing the knuckle height to the contralateral hand.

• Soft Tissue Assessment: Check for "fight bites" (human bites over the MCP joint) which require aggressive irrigation and antibiotics.

4. Radiological Findings

Standard imaging involves PA, Lateral, and Oblique views of the hand.

• Oblique View: Best for visualizing the degree of displacement in shaft fractures.

• Brewerton View: Specifically used to visualize the metacarpal head in cases of suspected intra-articular fractures.

•  Roberts View: Best view to see thumb CMC fracture/dislocation

• CT Scan: Reserved for complex intra-articular base fractures or CMC joint dislocations.

5. Classification Systems

Metacarpal fractures are generally classified by their anatomical location:

• Head Fractures: Usually intra-articular; require precise reduction.

• Neck Fractures: Extremely common in the 5th metacarpal (Boxer's fracture).

• Shaft Fractures: Can be transverse, spiral, or comminuted.

• Base Fractures: Often associated with CMC joint dislocations (e.g., Bennett’s or Rolando’s fracture in the thumb).

6. Treatment Strategies

Non-Surgical Treatment

Most metacarpal neck and shaft fractures can be treated conservatively if they meet stability criteria.

·       Acceptable Angulation: Higher degrees of angulation are tolerated in the 4th and 5th metacarpals (up to 30–40°) compared to the 2nd and 3rd (less than 10–15°) due to the mobility of the CMC joints.

• Immobilization: An ulnar or radial gutter splint is used, typically for 3–4 weeks.

• Buddy Taping: Used for very stable fractures to allow early range of motion (ROM).

Surgical Treatment

Indicated for unstable fractures, multiple metacarpal fractures, or significant rotational deformity.

• K-wire Fixation: A common, minimally invasive technique for neck and shaft fractures.

• ORIF (Plates and Screws): Provides rigid fixation, allowing for immediate post-operative mobilization.

• Lag Screws: Ideal for long spiral fractures.

Operative Treatment  İndication 

             open fx intra-articular fxs  

             rotational malalignment of dig

             significantly displaced or angulated fractures (see above criteria)

              multiple metacarpal shaft fractures

              loss of inherent stability from border digit during healing process postoperative early

         MOTION İS CRITICAL REMOVE PİNS/ CAST AT ~ 4 WEEKS

7. Prognosis and Complications

Prognosis: Excellent with proper alignment and early rehabilitation.

Complications:

• Stiffness: The most common complication, often due to prolonged immobilization.

• Malunion: Rotational malunion is particularly disabling, causing finger overlap during flexion.

• Grip Strength Reduction: May occur if significant shortening or angulation is left uncorrected.

• Extensor Lag: Can result from adhesions or significant apex-dorsal angulation.

8. Key Points (Summary)

• Rotation is King: Any clinical rotation requires surgical correction.

• Tolerance for Angulation: The 5th metacarpal is much more "forgiving" regarding angulation than the 2nd.

• Early ROM: Stability should be followed by early movement to prevent tendon adhesions.

• Check for Bites: Always inspect for skin breaks over the knuckles in punch-related injuries.

References

1. Rockwood and Green's Fractures in Adults: Provides comprehensive data on epidemiology and biomechanical deforming forces.

2. AO Foundation / ASSH Guidelines: The basis for treatment algorithms focusing on stability and early mobilization.

3. Journal of Hand Surgery (JHS): Ongoing research supports the move toward stable internal fixation to facilitate earlier rehabilitation.