Question
A 24 year old man punches a wall and has a painful, swollen thumb base. His radiograph is shown.
- What is the injury and which forces displace it?
- How is it managed?
- What are the complications?
Answer
Diagnosis
- Bennett fracture, an intra-articular fracture dislocation of the first metacarpal base
- Volar ulnar fragment stays attached to the anterior oblique (beak) ligament
- Metacarpal shaft subluxes dorsally, radially and proximally
Deforming forces
- Abductor pollicis longus pulls the base proximally and radially
- Adductor pollicis adducts and supinates the shaft
- Extensor pollicis longus adds proximal pull
Management
- Closed reduction with traction, pronation, abduction and pressure over the base
- Percutaneous K wires to the trapezium or second metacarpal when reduction holds
- ORIF with a lag screw for a large fragment or an articular step over 1 to 2 mm
- Thumb spica for 4 to 6 weeks
Complications
- CMC joint arthritis with a residual step
- Loss of reduction
- Stiffness and weak pinch
- Pin tract infection and superficial radial nerve injury
Related pages
Author Contributions
Orthofracs team
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.