Bennett Fracture: Causes, Diagnosis, Treatment & Recovery Guide
A Bennett fracture (also spelled Bennett's fracture) is the most common type of intra-articular fracture at the base of the thumb. Despite its seemingly simple appearance on X-ray, it is a **highly unstable injury** that requires precise diagnosis and timely treatment to prevent long-term disability, chronic pain, and arthritis. This comprehensive guide covers everything you need to know—from mechanism of injury to surgical options and rehabilitation.
What Is a Bennett Fracture?
A Bennett fracture is defined as a two-part intra-articular fracture separates the palmar ulnar aspect of the first metacarpal base from the remaining first metacarpal main body.
Crucially, this small fragment remains **anchored to the trapezium** (a wrist bone) by the strong anterior oblique ligament (also called the beak ligament). Meanwhile, the larger main fragment is pulled out of place by powerful thumb muscles—leading to displacement and joint instability.
How Does a Bennett Fracture Happen?
Bennett fractures typically occur due to:
- Axial force on a partially flexed thumb (e.g., punching a wall, falling on a clenched fist)
- Sports injuries (boxing, football, rugby)
- Motor vehicle accidents
When force drives the thumb into the palm, the base of the metacarpal impacts the trapezium, causing the bone to split. The intact ligament holds one piece in place, while muscles like the abductor pollicis longus and extensor pollicis brevis pull the main shaft fragment dorsally, radially, and proximally.
Bennett Fracture vs. Rolando Fracture vs. Pseudo-Bennett
Not all thumb base fractures are the same. Correct classification is critical:
| Fracture Type | Description | Stability | Prognosis |
|---|---|---|---|
| Bennett Fracture | Two-part intra-articular fracture with ligament-attached fragment | Unstable | Good with proper reduction |
| Rolando Fracture | Comminuted (3+ fragments), often “Y” or “T” shaped | Highly unstable | Poorer; higher risk of arthritis |
| Pseudo-Bennett (Epibasal) | Extra-articular fracture at base of metacarpal | More stable | Excellent with casting |
Symptoms of Bennett Fracture
If you’ve suffered a Bennett fracture, you may experience:
- Severe pain at the base of the thumb
- Swelling and bruising over the CMC joint
- Weakness in pinch grip (e.g., difficulty turning a key or opening a jar)
- Visible deformity or “missing knuckle”
- Inability to move the thumb without pain
Diagnosis: Imaging & Special Views
Standard X-rays (AP, lateral, oblique) are the first step—but they often miss subtle displacement. For accurate diagnosis, orthopedic specialists use:
- Robert’s View: True AP of the thumb CMC joint (forearm fully pronated, thumb flat on plate)
- Bett’s View: Lateral view of the CMC joint (palm pronated 15–35°, beam angled 15°)
- CT Scan: For complex cases or surgical planning—shows fracture alignment in 3D
Key radiographic signs:
- Intra-articular fracture line at thumb base
- Subluxation or dislocation of the first metacarpal
- Small ulnar fragment still articulating with trapezium
Bennett Fracture Treatment Options
Treatment depends on fracture displacement, patient age, activity level, and occupation.
Non-Surgical Treatment (Rare)
Only considered for truly non-displaced fractures** (<1 alignment.="" articular="" involves:="" joint="" mm="" p="" stable="" step-off="" with="">
- Thumb spica cast or splint for 3–4 weeks
- Close follow-up with repeat X-rays to monitor for displacement
Note: Most Bennett fractures displace during casting—making surgery the preferred choice.
Surgical Treatment (Gold Standard)
Recommended for **any displacement >1 mm** or joint instability. Goals: anatomical reduction, stable fixation, early motion.
Common surgical techniques:
- Open Reduction Internal Fixation (ORIF):
- Incision over the CMC joint (Wagner approach)
- Direct visualization and reduction
- Fixation with interfragmentary screw** (preferred) or K-wires
- Closed Reduction Percutaneous Pinning (CRPP):
- Reduction under X-ray guidance
- K-wires inserted through skin to hold fragments
- Less invasive but higher risk of loss of reduction
- Combined Fixation: K-wire from first to second metacarpal to control rotation
Screws vs. Pins: Screws provide stronger fixation and allow earlier motion. Pins require removal after 4–6 weeks.
Rehabilitation & Recovery Timeline
Recovery is gradual but predictable with proper rehab:
- Weeks 0–2: Thumb immobilized in splint; finger and wrist motion encouraged
- Weeks 2–6: Pins removed (if used); gentle active thumb motion begins
- Weeks 6–12: Strengthening exercises, grip training, scar massage
- 3–6 months: Full return to sports, manual labor, or heavy use
Physical or occupational therapy is essential to restore pinch strength, dexterity, and joint mobility.
Potential Complications
Without proper treatment, Bennett fractures can lead to:
- Post-traumatic osteoarthritis (most common)
- Chronic pain and stiffness
- Malunion or nonunion
- Persistent CMC joint instability
- Loss of pinch and grip strength
Studies show that patients with anatomic reduction (<1 mm="" step-off="" strong=""> have excellent outcomes—86% remain symptom-free long-term.
Frequently Asked Questions (FAQs)
Q: Is a Bennett fracture serious?
A: Yes. Despite its small size, it’s an unstable joint fracture that almost always requires surgery to prevent arthritis and disability.
Q: How long does it take to heal?
A: Bone healing takes 6–8 weeks, but full functional recovery can take 3–6 months with therapy.
Q: Can you treat a Bennett fracture without surgery?
A: Only if it’s truly non-displaced and stable. Most cases need surgery for best outcomes.
Q: What’s the difference between Bennett and Rolando fracture?
A: Bennett = 2 fragments; Rolando = 3+ comminuted fragments. Rolando has a worse prognosis.
Q: Why is the hitchhiker position bad after a Bennett fracture?
A: Thumb extension pulls the metacarpal shaft further out of place—worsening displacement.
Q: Can you fully recover from a Bennett fracture?
A: Yes—with timely surgery and rehab, most patients regain near-normal thumb function.
Conclusion
The Bennett fracture is a deceptively complex injury that demands expert orthopedic care. While it may look minor on X-ray, its instability and joint involvement make it a surgical priority in most cases. With modern fixation techniques and structured rehabilitation, patients can expect excellent functional outcomes and a return to daily activities, work, and sports.
If you suspect a thumb base fracture, seek evaluation by a hand or orthopedic trauma specialist immediately.
References
- Carlsen BT, Moran SL. Thumb trauma: Bennett fractures, Rolando fractures, and ulnar collateral ligament injuries. J Hand Surg Am. 2009;34(5):945–952.
- Kjaer-Petersen K, Langhoff O, Andersen K. Bennett's fracture. J Hand Surg Br. 1990;15(1):58–61.
- Cullen JP, et al. Simulated Bennett fracture treated with closed reduction and percutaneous pinning. J Bone Joint Surg Am. 1997;79(3):413–420.
- Edmunds JO. Traumatic dislocations and instability of the trapeziometacarpal joint of the thumb. Hand Clin. 2006;22(3):365–392.
- Gedda KO. Studies on Bennett's fracture; anatomy, roentgenology, and therapy. Acta Chir Scand Suppl. 1954;193:1–114.
- Radiopaedia.org. Bennett Fracture. Updated 2024.
- StatPearls. Bennett Fracture. NIH/NLM. Updated 2023.