Summary

Bennett's Fracture is an unstable, intra-articular fracture-subluxation of the Base of the 1st Metacarpal (Thumb). It is the most common thumb fracture. The injury is unstable due to two opposing forces: the Volar Beak Ligament holds the small triangular fragment in place attached to the trapezium, while the Abductor Pollicis Longus (APL) tendon pulls the main shaft proximally, dorsally, and radially. Because of this constant deforming force, conservative management (casting) almost always fails. Surgical Fixation (K-wires or Screws) is the Gold Standard to restore the articular surface and prevent debilitating post-traumatic arthritis of the CMC joint. [1,2,3]

Key Facts

• The Trap: The small piece (volar-ulnar fragment) stays put. The BIG piece (the rest of the thumb) dislocates.
• The Deforming Force: The APL (Abductor Pollicis Longus) is the enemy. It pulls the shaft proximally. The Adductor Pollicis pulls the head into adduction.
• The Rolando Fracture: This is a comminuted version of Bennett's (3 parts, Y or T shaped). It is much harder to fix and has a worse prognosis.
• Threshold: Any articular step-off >1mm usually mandates surgery in active patients.

Clinical Pearls

"The Pull of the APL": You can reduce a Bennett's fracture easily in the ED. But as soon as you let go (or even put it in a cast), the APL pulls it out of place again. It is inherently unstable.

"Bennett vs Rolando":

• Bennett: 2 parts. Oblique line. Fixable with K-wires/Screws.
• Rolando: 3+ parts. T or Y shape. "Smashed". Typically requires a Plate or External Fixator.

1. Bennett's Fracture

• Definition: 2-part intra-articular fracture.
• Fragment: Volar-Ulnar.
• Management: CRPP (Wires) or Screw.

2. Rolando Fracture

• Definition: 3-part (or comminuted) intra-articular fracture.
• Pattern: "Y" shaped or "T" shaped.
• Prognosis: Worse than Bennett's.
• Management: Plate or Ex-Fix (Distraction).

3. Extra-Articular (Epibasal)

• Definition: Transverse fracture distal to the joint.
• Stability: Stable. Can be treated with a cast. (Essentially a "Boxer's fracture of the thumb").

                  THUMB BASE FRACTURE
                          ↓
            INTRA-ARTICULAR OR EXTRA-ARTICULAR?
            ┌─────────────┴─────────────┐
      EXTRA-ARTICULAR             INTRA-ARTICULAR
         (Epibasal)                     ↓
            ↓                   COMMINUTED? (Y-Shape)
           CAST                 ┌───────┴───────┐
      (Thumb Spica)            NO              YES
                            (Bennett)       (Rolando)
                                ↓               ↓
                         DISPLACED >1mm?      SURGERY
                         ┌──────┴──────┐    (Plate/Ex-Fix)
                        NO            YES
                        ↓              ↓
                      CAST          SURGERY
                    (Watch)      (K-Wire/Screw)

1. Conservative (Rare)

• Indication: Truly undisplaced fractures (step <1mm) in low-demand patients.
• Device: Thumb Spica Cast.
• Surveillance: Weekly X-rays are mandatory. Most slip.

2. Surgical: CRPP (K-Wiring)

• Indication: Most Bennett's fractures.
• Technique (Iselin):
  1. Traction + Pronation + Abduction (Reduction Maneuver).
  2. Drive 1.6mm K-wire from Metacarpal Shaft -> Trapezium (Trapezial wire).
  3. Optional: Drive K-wire from 1st MC -> 2nd MC (Intermetacarpal wire).
• Pros: Minimally invasive. Low risk.
• Cons: Wire issues (infection/backing out). Cast needed for 6 weeks.

3. Surgical: ORIF (Screw/Plate)

• Indication: Large volar fragment (>20% of surface) or Rolando fracture.
• Device: 2.0mm Lag Screw or T-Plate.
• Approach: Wagner (Radiovolar) approach. Beware Radial Nerve and Artery.

Livesley (1990)

• Long term follow-up (26 years).
• Finding: Conservative treatment of Bennett's fracture led to degenerate radiographic changes (OA) in all cases, and symptoms in most.
• Conclusion: Surgical anatomical reduction is superior.

Soyer (1999)

• Comparing CRPP (Closed Pinning) vs ORIF (Open Screw).
• Finding: Results were similar. ORIF had higher complication rate (nerve issues).
• Conclusion: CRPP is the safer first-line option. Reserve ORIF for large fragments or failure of reduction.

What is a Bennett's Fracture?

The bone at the base of your thumb has split into two pieces. One piece is held tight by a ligament (like an anchor), but the rest of your thumb has been pulled away by the strong tendons.

Do I need surgery?

Yes. If we just put it in a cast, the tendons will pull it out of place again as soon as the muscle twitches. We need to "lock" it in place with a metal pin or screw.

What does the surgery involve?

Usually, we can do it with "Keyhole" surgery (K-wires). We pull the thumb straight and insert 2 metal pins through the skin to hold it. You wear a cast for 6 weeks, then we pull the pins out in the clinic (it doesn't really hurt).

Will I get arthritis?

Because the break goes into the joint, there is a risk of arthritis (wear and tear) later in life. Surgery minimizes this risk by lining the surface up perfectly smooth, but it doesn't eliminate it completely.

Q1: What are the deforming forces in a Bennett's Fracture? A: 1. APL (Abductor Pollicis Longus): Pulls the shaft Proximally, Dorsally, and Radially. 2. Adductor Pollicis: Pulls the head into Adduction. 3. Volar Beak Ligament (AOL): Anchors the triangular volar fragment to the trapezium (preventing it from moving).

Q2: Describe the Rolando Fracture. A: A comminuted (3-part or more) intra-articular fracture of the 1st Metacarpal base. It typically has a "Y" or "T" pattern. It has a poorer prognosis than Bennett's and often requires plating or external fixation.

Q3: What is the "Robert's View"? A: A true AP of the thumb. The hand is hyper-pronated (flat on cassette) to visualize the CMC joint profile without overlap. Essential for assessing articular step-off.

(End of Topic)