This Daily Doodle illustrates a Boxer’s Fracture, a fracture across the distal neck of the fifth metacarpal bone. Boxer’s fractures account for ~10% of all hand fractures.

Mechanism of injury: “Direct trauma to a clenched fist, such as punching a wall or solid object. The “roundhouse” punching motion common in street fights (but rare in professional or high level amateur boxing) generally transmits significant force to the fifth metacarpal, resulting in fracture. Experienced boxers rarely sustain this type of fracture, and the term “boxer’s fracture” is therefore a misnomer” [1].

Here is a mnemonic to help remember an approach to describing a fracture on an x-ray, “Comment on the 6-A’s”:

1. Anatomy: Where is the fracture located? What type of fracture is it: transverse, oblique, comminuted, impacted…)?
2. Articulation: Does the fracture involve the articulating surfaces of a joint?
3. Alignment:  —What is the relationship of the longitudinal axis of one fracture segment, or bone, to another? (Alignment is often used interchangeably with the term “dislocation”).
4. Angulation: —Is there any rotational deviation from normal alignment? If yes, describe the angulation in degrees of the distal fragment in relation to the proximal fragment.
5. Apex: In addition to describing the degree of angulation, the direction the apex is pointing relative to anatomical long axis of the bone (e.g. apex medial, apex valgus) should also be included.
6. Apposition: Describe the amount of end to end contact of the fracture fragments.

In addition to the 6-A’s, don’t forget to comment on the ABCs: Adequacy (confirm patient ID, date, exposure , views), Bones (look for other fractures, lesions, evidence of disease such as OA), Cartilage and Soft-tissues [2].

Most closed metacarpal neck fractures can be treated non-operatively with dorsal block cast or ulnar gutter splint for ~4 weeks. K-wire fixation may be required if reduction cannot be maintained. Internal fixation with plates is the last resort. Here is a simple rule to determine if surgical management is required based on angulation, it is called the  “10, 20, 30, 40 rule”. As described in the Uptodate article, “The second metacarpal neck tolerates 10 degrees of angulation, the third 20 degrees, the fourth 30 degrees, and the fifth metacarpal up to 40 degrees of angulation without adversely affecting functional outcome. However, some researchers believe the threshold for fifth metacarpal fractures should also be 30 degrees” [1].

** Please keep in mind that this is just a quick doodle. X-rays are quite difficult to sketch using a pencil crayon!

References

1. J. Bloom. “Metacarpal neck fractures”. Uptodate. http://www.uptodate.com/contents/metacarpal-neck-fractures?source=search_result&search=boxers+fracture&selectedTitle=1~4
2. N. Patel. “Basics of Orthopedic Radiology”. St. Joseph’s Regional Medical Center. Paterson, NJ. November 2008.

“Boxer’s Fracture” Medical Daily Doodle by Michiko Maruyama