Summary

A Boxer's Fracture is a fracture of the 5th Metacarpal Neck (Little Finger), accounting for 20% of all hand fractures. Classically caused by punching a hard object with an improper technique (axial load on the 5th knuckle), it results in volar angulation of the metacarpal head. The key concept is that the 5th Carpometacarpal (CMC) joint is a highly mobile saddle joint (20-30° range), allowing significant compensation. Therefore, angulation up to 70° is functionally tolerated and can be managed conservatively with Buddy Taping. The absolute indication for surgery is Rotational Deformity (Scissoring), which is not tolerated. "Fight Bites" (teeth marks) are surgical emergencies requiring washout for Eikenella corrodens. [1,2,3]

Key Facts

• The Mobility Rule: The 2nd/3rd CMC joints are rigid (0° motion). Hand fractures here tolerate no angulation. The 5th CMC is mobile (30° motion). Fractures here tolerate massive angulation.
• Jahss Maneuver: The reduction technique for severe angulation (>70°). Flex MCP/PIP to 90°, push dorsal on the P1.
• The "Lost Knuckle": Even with perfect healing, the 5th knuckle will be permanently depressed (loss of prominence). This is cosmetic, not functional. Warn the patient early.

Clinical Pearls

"Look for the Tooth Mark": A 3mm laceration over the knuckle is a Human Bite until proven otherwise. The extensor tendon retracts when the hand opens, dragging bacteria (Eikenella) deep into the joint. It causes septic arthritis within 24 hours.

"Check Rotation, Not Just Angulation": X-rays show the bend. The clinical exam shows the twist. Ask the patient to make a fist. All fingers should point to the Scaphoid Tubercle. If the little finger crosses under the ring finger ("Scissoring"), they need surgery.

"Antibiotics for Bites": If there is a bite, give Co-Amoxiclav. Flucloxacillin (standard skin Abx) does NOT cover Eikenella.

Angulation Severity

• Mild: <15° (Normal neck angle is 15°).
• Moderate: 15-40°.
• Severe: 40-70°.
• Extreme: >70°.

Stability

• Stable: No rotation. Angulation accepts correction.
• Unstable: Rotational deformity. Comminuted. Open.

                 BOXER'S FRACTURE
                        ↓
            IS THERE MALROTATION (Scissoring)?
            OR IS IT OPEN (Fight Bite)?
           ┌────────────┴─────────────┐
          YES                        NO
           ↓                          ↓
        SURGERY                 CHECK ANGULATION
     (K-Wires / Washout)        ┌─────┴──────┐
                              <70°          >70°
                               ↓             ↓
                          CONSERVATIVE    REDUCTION
                         (Buddy Strap)      (Jahss)
                         (Mobilise!)         ↓
                                          STABLE?
                                        ┌────┴────┐
                                       YES       NO
                                        ↓         ↓
                                      STRAP     SURGERY

Indication

• Closed fracture.
• No rotation.
• Angulation <70° (Most cases).

Protocol: "Buddy Taping"

• Technique: Strap Little Finger to Ring Finger.
• Rationale: The Ring finger acts as a splint. Allows immediate movement.
• Mobilisation: Crucial. Stiffness is the enemy.
• Avoid: Ulnar Gutter Casts (immobilising in flexion). Evidence shows poorer outcomes (stiffness/sores) compared to taping.

Reduction (The Jahss Maneuver)

• Indication: Angulation >70° or pseudoclawing.
• Technique:
  1. Blocks (Ulnar Nerve / Haematoma).
  2. Flex MCP and PIP to 90°.
  3. Push UP on the P1 (Proximal Phalanx) while pushing DOWN on the Shaft.
  4. The collateral ligaments tighten and pull the head back.

Fight Bite Protocol

• Urgent: Debridement and Washout in theatre.
• Antibiotics: IV Co-Amoxiclav.
• Closure: Leave open. Never suture a bite wound.

Fracture Fixation

• K-Wiring:
  • Bouquet Technique: Multiple bent wires inserted from the base of the metacarpal (intramedullary). Minimally invasive. No wires sticking out of skin.
  • Transverse Pinning: Pinning to the 4th Metacarpal.
• ORIF (Plate): Rare. For complex comminuted fractures.

Acceptable Angulation (Ali et al. 2010)

• Cadaveric and Clinical study.
• Found that up to 70° of neck angulation does not impair flexor tendon excursion or grip strength.
• Conclusion: There is no functional benefit to reducing fractures with <70° angulation.

Taping vs Casting (Poolman et al. Cochrane 2005)

• Review: Conservative Treatment for 5th MC fractures.
• Result: Functional bracing (taping) gave better range of motion and satisfaction scores than casting. No difference in pain.
• Recommendation: Treat with buddy taping.

What is broken?

You have snapped the neck of the bone leading to your little finger. It has bent forwards into your palm.

Do I need it pushed back (set)?

Surprisingly, no. Imagine a door hinge (your knuckle). Even if the hinge is tilted forward 40 degrees, the door (your finger) can still swing open and closed perfectly fine because the joint is so flexible. We only need to fix it if the door is twisted (rotated) so it hits the doorframe.

Will my hand look normal?

No. You will lose the "bump" of your 5th knuckle. It will look flat. This is permanent. But your hand will work normally.

Why no cast?

Casts make hands stiff. Stiff hands are useless. By taping your fingers together, you can move them immediately. This pumps away the swelling and stops the stiffness.

FIGHT BITE WARNING

"Did this happen on a tooth?" If there is even a tiny cut, tell us. Human saliva is toxic to joints. If we miss a bite infection, it can destroy your knuckle joint in 2 days.

Q1: Why does the 5th Metacarpal tolerate so much angulation? A: The 5th CMC joint is a saddle joint with 20-30° of flexion/extension arc. This allows the patient to compensate for the fixed flexion deformity of the fracture. The 2nd/3rd CMC joints have 0° motion (rigid pillars), so they tolerate almost no angulation.

Q2: What is the specific antibiotic for a Human Fight Bite and why? A: Co-Amoxiclav (Augmentin). It covers Eikenella corrodens (a Gram-negative facultative anaerobe resistant to Flucloxacillin/Erythromycin/Clindamycin) as well as Staph and Strep.

Q3: Describe the Intramedullary "Bouquet" technique. A: A minimally invasive fixation where multiple pre-bent K-wires are inserted antegrade through the base of the 5th metacarpal, up the shaft, fanning out into the head to support the reduction. It avoids pin tract infections and extensor tendon tethering seen with retrograde pinning.

(End of Topic)