First Metacarpal Fractures:

There are two types of fractures that commonly occur at the base of the 1st metacarpal.  They are:

Bennett Fracture:  This is an intraarticular fracture at the base of the 1st metacarpal that always involves some degree of subluxation or dislocation of the 1st carpometacarpal joint. 

Image from Wikipedia Commons

• This is the most common fracture of the thumb. 
• This fracture is typically caused by axial loading the thumb while the metacarpal is partially flexed.  A common mechanism is when a person punches a wall or hard object with their thumb take the brunt of the force.
• Most of these fractures will require surgical repair but can be treated in the ED with a Thumb Spica Splint.

Rolando Fracture:  This is a communited intraarticular fracture at the base of the first metacarpal that typically has a T or Y shaped configuration with 3 fragments.

Image courtesy of WikiPedia Commons

• Less common then Bennett Fractures
• Associated with a worse prognosis
• Requires surgical repair but can be splinted in the ED with a thumb spica splint.