Mallet finger

The term mallet finger describes an injury, which results in an inability to extend the end of the finger. The injury is often caused by relatively benign trauma, such as catching finger on clothing. It can also be caused by a forceful blow to an extended finger, for example from a cricket ball, or as a consequence of a fall from a bicycle.

Patients report that the end of the finger droops. The tendon responsible for lifting the distal phalanx (the last bone in the finger), is torn or stretched. A small fragment of bone may have pulled away with the tendon, and very-occasionally the normal position of the finger bones can become disrupted, with partial dislocation at the distal inter-phalangeal joint.

The majority of mallet finger injuries can be described as closed, and no disruption of the skin. Less commonly the injury can be described as the skin can break, or a cut across the top of the finger, for example from a knife, or from broken glass, can result in a divvision of the tendon.

Treatment

Closed mallet injuries, with no sign of any potential displacement or dislocation of the distal phalanx, should be treated with a splint to hold the finger joint in extension (or slight hyperextension). I would recommend a continuous period of splinting of 6 weeks. If this is interrupted at any point, the six-week period starts again. At this the splint is removed in clinic, if there is any drooping of the distal phalanx, the splinting is continued for a further 4-6 weeks.

Investigation

The evidence suggests that very few closed mallet finger injuries need surgery. Review of the outcome in patients with small avulsion fractures, suggests that there is no significant improvement in outcome as a consequence of surgery (irrespective of the size of the avulsed bone fragment.). Patient’s who have dislocation of the distal inter-phalangeal joint, will however benefit from early surgery. Patients with open mallet finger injuries in which the extensor tendon is cut, can potentially benefit from surgery. This is under local anaesthetic as a day case procedure.

Delayed presentation

Patients who present at clinic, weeks or months after a closed mallet finger injury, can still benefit from splinting.

Types of splint

Some patient's will fabricate her own splint from a lollipop stick, this is a reasonable thing to do at the time of injury in order to start the 6 week period of continuous splinting. I would recommend use of either a Zimmer splint on the dorsum of the finger, or a thermo-plastic splint fabricated by hand therapist. I would recommend that the patient be allowed to flex freely at the proximal inter-phalangeal joint.

I do not think the off-the-shelf splints issued by most emergency departments consistently provide adequate support to the distal phalanx, I am not convinced that they splint the distal phalanx appropriately in slight hyperextension. I have seen several patients who have had significant problems with the skin on the back of her finger as a consequence of the continued use of tight plastic off-the-shelf splint.

Zimmer splint

Return to sport

I am happy for patients to return to sport once a well fitted splint is in place, provided the presence of the splint is not causing significant risk to themselves, or to other competitors. Most contact sports will allow the use of the splint provided it is covered by Elastoplast™ tape. I would suggest that patients discuss this with their coach, match officials, and if need be the governing body of their sport.

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