(See also Overview of Fractures Overview of Fractures A fracture is a break in a bone. Most fractures result from a single, significant force applied to normal bone. In addition to fractures, musculoskeletal injuries include Joint dislocations... read more 
.)
This discussion pertains to fractures of the metacarpal bones other than the thumb metacarpal. Fractures of the neck of metacarpals 2 through 5 are common. They cause pain, swelling, tenderness, and sometimes deformity. Rotational deformity Rotational deformity due to a fracture in the hand 
may occur. The 5th metacarpal is most commonly injured by punching (boxer's fracture). When these fractures result from punching someone in the mouth, human oral flora may contaminate the wound, sometimes causing infection. Patients with fight bites require antibiotics Infected Bite Wounds of the Hand A small puncture wound, particularly from a human or cat bite, may involve significant injury to the tendon, joint capsule, or articular cartilage. The most common cause of human bites is a... read more .
Rotational deformity due to a fracture in the hand
Normally, when the proximal interphalangeal joints are flexed to 90°, lines from the distal phalanges converge at a point on the proximal carpal bones. Deviation of one of these lines suggests a metacarpal fracture.  |
Diagnosis of Metacarpal Neck Fractures
X-rays
The 5th metacarpal neck bone is fractured midshaft.
LIVING ART ENTERPRISES, LLC/SCIENCE PHOTO LIBRARY
This colored x-ray shows a fracture of the 5th metacarpal neck. In this view, angulation appears to be < 45°, suggesting that reduction is not necessary.
SCOTT CAMAZINE/SCIENCE PHOTO LIBRARY
Typically, anteroposterior, lateral, and oblique views are diagnostic.
Treatment of Metacarpal Neck Fractures
Prophylactic antibiotics for open wounds
Splinting
For certain fractures, reduction
If patients have any wounds, particularly linear punctures, near the metacarpophalangeal joint, they should be specifically questioned about whether they punched someone in the mouth. If they did, contamination with human oral flora is possible, and measures to prevent infection (eg, wound exploration and cleaning, prophylactic antibiotics Antimicrobials Human and other mammal bites (mostly dog and cat bites, but also squirrel, gerbil, rabbit, guinea pig, and monkey bites) are common and occasionally cause significant morbidity and disability... read more ) are often required.
Treatment of a metacarpal neck fracture is with a splint (eg, an ulnar gutter splint Ulnar gutter splint 
for fractures of the 4th or 5th metacarpal), usually for at least a few weeks. Whether reduction is needed before the splint is applied depends on the fracture.
Reduction is not necessary for dorsal or volar angulation of
< 35° for the 4th metacarpal
< 45° for the 5th metacarpal
Reduction is necessary for
Rotational deformity of any metacarpal
Fractures of the 2nd and 3rd metacarpals with angulation
Usually, closed reduction is possible. Use of a hematoma block or an ulnar nerve block can help reduce the pain during reduction.
After the splint is removed, patients can gradually begin range-of-motion exercises.
Ulnar gutter splint
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Key Points
Metacarpal neck fractures cause pain, swelling, tenderness, and sometimes deformity (eg, rotational deformity).
Take anteroposterior, lateral, and oblique x-rays.
If patients have wounds near the metacarpophalangeal joint, ask them whether they punched someone in the mouth; if they did, take measures to prevent infection (eg, prophylactic antibiotics).
Treat a metacarpal neck fracture with a splint; if angulation is significant or if rotational deformity is present, reduce the fracture first, usually using closed reduction.
