What Is the Metacarpus?

The metacarpus refers to the five long bones in the palm. These bones are called metacarpals, are cylindrical, and are numbered from one to five. The first metacarpal is located under the meaty part of the thumb in the palm, and the fifth is located at the outside edge of the hand under the smallest finger. Injuries, such as fractures, can occur in any of the bones that make up the metacarpus, and will require treatment and rehabilitation.

Each metacarpal has a base, or carpal extremity, and a head, or digital extremity. The base connects with the carpus, which is the name of the shorter, closely packed group of bones located in the wrist at the base of the hand. Each metacarpal's head connects with the finger bones, known as phalanges, at the knuckle of the corresponding finger, known as the metacarpophalangeal joints. A number of different muscles and tendons connect to and surround the metacarpals, including the interossei, which are the small muscles that lie below and between the metacarpals, and specialist muscles that control the motion of each of the fingers.

A fracture in the metacarpus means that one of the five metacarpals has broken, usually after some kind of blunt trauma. This injury is more common in males who play full contact sports than any other group of people. A broken fifth metacarpal is called a boxer's fracture, and is the most common metacarpal injury. Rolando's fracture, a crushed break in the thumb, is also common, as is Bennett's fracture, a non-crushed break in the thumb.

If the metacarpus has been injured, the person will need to wear a brace, cast, or more complex metal device involving pins and screws while the bones heal, but the specifics depend on the severity and type of fracture. Surgery may be required to set the bones, particularly if the metacarpus has been crushed or otherwise seriously damaged. It is especially important that injuries to the first, second, and third metacarpals are treated promptly because improper healing in this area can significantly affect hand function.

Physical rehabilitation is important after a metacarpal injury. This is used to restore normal hand function and prevent lingering hand pain or stiffness. The prognosis is very good for most metacarpal injuries, and patients are usually able to painlessly resume all activities after healing is complete, which might be anywhere from several weeks to a year or more in the case of serious injury or extensive surgery. Some patients may need further surgery if complications arise, such as difficulty gripping or extending the hand.