Neck of 5th Metacarpal Fractures

Neck of fifth Metacarpal (Boxer’s) fractures are a common injury, and how we treat them locally is changing.

 

xray showing a fracture of the neck of the 5th metacarpal bone of the hand
James Heilman, MD [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

A boxers fracture is a fracture, normally transverse, through the neck of the fifth metacarpal and often displaying some degree of volar angulation.

The classical mechanism is punching something hard, such as a wall or someone’s head.

I would argue that it would be better classified as a ‘brawler’s fracture’ as people who are trained to fight generally strike with the 2nd/3rd metacarpal region where the force is more dissipated and the metacarpals better splinted by surrounding structures. It is the casual swing catching the 5th metacarpal, that is most likely to cause injury.

Of course other mechanisms, such as a direct blow to the hand, are available.

It is important to carefully and sensitively question patients presenting with this kind of injury. When the injury is from punching a person, they may offer an alternative such a punching a wall or punch bag in fear of ‘getting into trouble’. When the prior they may suggest a different mechanism out of embarrassment or concern that we will question their emotional health, which indeed we should be doing.

Anecdotally, I note an increase in presentation of children and young people attending with hand injuries from ‘punching a wall’ out of anger or frustration, and care should be given to consider the patients emotional and/or mental health, do they need intervention for anger management, are there safeguarding issues for themselves or other children/family members. Ultimately this can be considered a form of self harm and assessment should be given with this in mind.

Care should be given to wounds, however minor, associated with these injuries and where there are wounds an increased level of suspicion regarding the mechanism of injury is appropriate. If the wound is from striking an human tooth, a so called “fight bite”, then this makes a significant difference to the treatment, and the same should be clearly explained to the patient.

An image of a closed hand showing normal anatomical position of fingers
Normal cascade of the fingers

Fracture at the neck of the MC can cause rotational deformity of the distal structures. This will at least need specialist assessment and is likely to need some form of correction. If left untreated this can lead to persistent problem with fist formation and disability of the hand. Look out for a small finger that appears to cross medially toward or under the other fingers when a fist is formed, rather than falling inline. In a normal cascade with fingers flexed to 90 degrees at the MCPJ and PIPJ all fingers should point toward the scaphoid tubercle. Compare to the other hand.

 

Examination

Undertake the usual examination process for a hand injury. Particularly note:

  • Swelling, bruising or deformity in the distal 5th MC region. Normally swelling and deformity are more notable dorsally. Palmer bruising should increase your suspicion of fracture.
  • Any wounds to the hand, especially wounds to the distal MC,  and MCPJ region. Carefully assess the wound depth and try to illicit good history of injury.
  • Flexion/fist formation of the hand. With particular attention to cascade of the small finger.

Xray

  • Fracture likely to present as above, transverse across neck.
  • Degree of volar angulation should be noted. Up to 60 degrees volar angulation acceptable.

 

Treatment

Closed, extra-articular injures with less than 60 degree of volar angulation (but NO rotational deformity) can be managed with buddy strapping of the small and ring fingers and referral to virtual fracture clinic.

Closed, extra-articular injuries with more that 60 degree volar angulation should be reduced in the ED under haematoma block. See below

Open injuries should be irrigated with copious amounts of saline and discussed with plastics on call with a view to surgical debridement and closure. Apply antimicrobial dressing, buddy strap  and commence oral antibiotics.

Fractures with ANY rotational deformity of the small finger and fractures with dorsal angulation of the distal part should be discussed with plastics on call. Buddy strap and apply an ulna gutter slab.

Fractures of other than the metacarpal neck (i.e head, shaft or base) or other than the 5th metacarpal are not covered by this guidance but broadly should be buddy strapped, immobilised and referred to virtual fracture clinic. Unless complex – consider referring to plastics on call.

Fractures with concurrent nerve, tendon or other complication should be treated as per usual protocol.

 

Reduction of Boxers Fracture

Most literature recommends the 90-90 or Jahss method of reduction.

Once anaesthetised the small finger is gently put under traction to dis-impact the fracture then, with the MCPJ and PIPJ flexed to 90 degrees, pressure is put on the dorsum of the midshaft 5th MC and the distal proximal phalanx in a pinching motion to force the head of the metacarpal back into alignment.

The hand should be re-xrayed to check alignment, rechecked for rotational deformity, and buddy strapping and ulna gutter applied.

If the angulation is resolved to within acceptable limits and no rotational deformity then refer virtual fracture clinic. If not refer plastics acutely.

The below animation illustrates the mechanics involved nicely.

 

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