A mallet finger is a disruption of the extensor tendon that straightens the tip of the finger. The tendon may snap or pull off the bone, or pull a chip off the bone with it. This results in an inability to actively straighten the tip of the finger.
What causes a mallet finger?
A soft tissue mallet finger injury, where the tendon snaps or pulls off the bone, commonly occurs from a blow to the fingertip or even with minor activities. This may be as simple as pulling up a sock or tucking in a bed sheet. Injuries from a larger force are more likely to produce a bony mallet finger injury, where a fragment of bone is pulled off by the tendon.
How is the diagnosis made?
The diagnosis is usually fairly clear by looking at the finger. The tip of the finger droops down, and it is impossible to straighten the tip of the finger without using another hand to straighten it. Pain and swelling can be quite variable between patients, with some patients reporting no pain at all.
What tests are required?
The only test required is an x-ray. This will help determine whether the injury involves only the tendon or the bone as well. The x-ray will also determine if there has been dislocation of the joint, as these particular injuries usually require an operation.
How is mallet finger treated?
The most important principle is the keep the fingertip straight at all times, to allow the extensor tendon a chance to heal to its proper location. If there is a large bony fragment or any joint dislocation, then an operation may be recommended.
You will usually be referred to a hand therapist to have a mallet finger splint fitted. These come in various forms, but the essential nature is to comfortably immobilise the tip of the finger in a fully-straight position. The other joints of the finger should be free to move to prevent stiffness.
The splint will need to be removed for cleaning and drying, but it is essential that the fingertip is kept straight at all times. Before removing the splint, place the finger against the wall or other firm surface, then slip the splint off. Use the wall to keep the fingertip straight. If you need to move your finger off the wall, then use your other hand to keep the fingertip straight at all times. Allowing the fingertip to bend even once for a split second will break the early healing tendon, putting your healing back several days or weeks, or leading to failure of treatment.
If there is a bony component to the injury, then you may require frequent x-rays to ensure that the fragment is not displacing and that the joint is not dislocating.
The tendon heals slowly, so it will be at least 6-10 weeks before consideration is made to remove the splint. At this time, you will be assessed. If the tendon is functioning acceptably, then a weaning process will be started over a number of weeks. This process varies from patient to patient.
A large bony fragment will allow the joint to dislocate. If the joint is dislocated on x-ray, or if there is a large enough bone fragment that dislocation is inevitable, then an operation will be recommended to fix the bone fragment and the joint. Surgery is done as a day-only procedure in a hospital.
Depending on the individual scenario, this may be done with pins (called K-wires) through the skin without opening the fracture, or by an open operation to accurately reconstruct the joint. In most instances, there will be some sort of hardware that needs removal in the office about 6 weeks later.
What to expect after the operation
A dressing and a supplementary splint will be applied in the operating room at the end of the operation. The finger may be numb from local anaesthetic, which usually wears off after several hours. The hand should be kept dry and elevated.
The first follow-up appointment may be with the surgeon or with the hand therapist, depending on the individual circumstance. Stitches will be removed and a smaller mallet finger splint fashioned. If there is any hardware left protruding from the skin, then it needs to be kept clean and dry. The hardware is usually removed in the office at about 6 weeks after the initial surgery, and a splint weaning protocol started over a number of weeks.
What are the long-term outcomes?
Without treatment, patients have a fingertip droop that gets in the way of many activities, such as putting the hand in a pocket or catching a football. With proper treatment, most patients return to just about full activities. It is still common to have some residual droop of the fingertip, perhaps up to 15°, but there is still enough control over the fingertip for everyday use.
If there is failure of tendon of bone healing, then the joint can be fused with minimal functional loss. Likewise, if arthritis of the joint develops, then joint fusion can give good restoration of pain-free function.
Complications from mallet finger fixation surgery are uncommon. The usual risks are:
- Wound healing problems
- Pain and stiffness
- Failure of tendon or bone healing
- Complex regional pain syndrome
Note: This information is current at the date of original writing and is intended as a general guide only. It may or may not be relevant to any particular person’s circumstances. You should not rely solely on this information to guide management of your medical condition, but should discuss your own situation with your doctor.