Fifth Metacarpal Neck Fracture - Boxer's Fracture
- About the Boxer’s Fracture
Fifth Metacarpal Neck Fracture (Boxer’s Fracture)
Steven J. Meyers, MD, and Michael L. Lee, MD
Background
Metacarpal neck fractures are among the most common fractures in the hand. Fracture of the fifth metacarpal is by far the most frequent and has been termed a boxer’s fracture because the usual mechanism is a glancing punch that does not land on the stronger second and third metacarpals.
Clinical History and Examination
Patients usually have pain, swelling, and loss of motion about the MCP joint. Occasionally, a rotational deformity is present. Careful examination should be performed to ensure that there is no malrotation of the finger when the patient makes a fist (Fig. 1–33), no significant prominence of the distal fragment (palmarly displaced) in the palm, and no extensor lag of the involved finger.
Radiographic Examination
On the lateral radiograph, the angle of the metacarpal fracture is determined by drawing lines down the shafts of the metacarpal and measuring the resultant angle with a goniometer.
Treatment
Treatment is based on the degree of displacement, as measured on a true lateral of the hand (Fig. 1–34). Metacarpal neck fractures are usually impacted and angulated, with the distal fragment displacing palmarly because of the intrinsic muscle pull. Excessive angulation causes loss of the MCP joint knuckle and may cause the palmar metacarpal head to be prominent during activities. Only about 10 degrees of angulation can be accepted in second and third metacarpal neck fractures, whereas up to 30 degrees in the fourth metacarpal and 40 degrees in the fifth metacarpal can be accepted because of greater mobility in the fourth and fifth CMC joints.
If displacement is unacceptable, closed reduction can be attempted with wrist block anesthesia using the maneuver credited to Jahss (1938), in which the proximal phalanx is flexed to 90 degrees and used to apply a dorsally directed force to the metacarpal head (Fig. 1–35). The hand is then splinted in an ulnar gutter splint for about 3 weeks with the MCP joint at 80 degrees of flexion, the PIP joint straight, and the DIP joint free (Fig. 1–36).
Rapid mobilization of the fingers is required to avoid scarring, adhesions, and stiffness unrelated to the fracture itself but rather to the propensity of an immobilized hand to quickly stiffen.
Operative treatment of boxer’s fractures is indicated if
- Fracture alignment remains unacceptable (>40 degrees displacement).
- Late redisplacement occurs in a previously reduced fracture.
- There is any malrotation of the finger.
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Operative fixation usually involves percutaneous pinning of the fracture, but ORIF may be required.
Fractures treated operatively still require about 3 weeks of immobilization.
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