Metacarpal base fractures
- Josh Bloom, MD, MPH
Josh Bloom, MD, MPH
- Clinical Instructor, Department of Family Medicine
- University of North Carolina at Chapel Hill
Metacarpal fractures are common . They account for 30 to 40 percent of all hand fractures. Fractures of the base of the metacarpal bones may be the result of direct or indirect trauma.
This topic will review issues related to fractures of the base of the metacarpal. A general overview of metacarpal fractures is presented separately. (See "Overview of metacarpal fractures".)
Although first (thumb) metacarpal fractures typically occur at the base, the anatomy and biomechanics of the thumb are unique and fractures of the metacarpal of the thumb are presented separately. (See "First (thumb) metacarpal fractures".)
Fractures of the metacarpal base are provided a degree of stability due to the dorsal and palmar carpometacarpal ligaments as well as the interosseous ligaments. This is particularly true for second and third metacarpal base fractures. Fractures of the fourth and the fifth metacarpal base are somewhat less stable due to increased mobility at the carpometacarpal (CMC) joint. In addition, the motor branch of the ulnar nerve runs in close proximity with the fourth and fifth metacarpal bases, and accordingly, fractures of these areas warrant a thorough evaluation of ulnar-distributed motor function.
The fifth metacarpal CMC joint surface slopes in ulnar fashion, and is only buttressed on the radial side (by the fourth metacarpal and the hamate bone). The tendon of the powerful extensor carpi ulnaris muscle attaches on the ulnar aspect of the fifth metacarpal base, making it common for fractures here, particularly intraarticular fractures, to have a large fragment displaced in an ulnar and proximal direction.