by Alan Greene, MD, FAAP
A mother asks Dr. Greene, "My 15-month-old recently got her finger smashed in the door by her 2-year-old sister. I kept an eye on the nail and noticed it got yellowish, and within a week or so it had fallen off and was just attached at the cuticle. I trimmed it down as far as I could. There is a very thin nail coming in underneath. Do I keep this fingernail covered up somehow or let it breathe? How long until a new, normal, strong nail comes in?"
Slam! Smash! Slam! I vividly remember three separate finger-in-the-door episodes from my childhood. In one instance I was the culprit, inadvertently slamming a door on my friend Fernando's finger. Twice I was the "smashee" once with my finger caught in the door of my parents Chevy Nova and once in my own bedroom door.
It's not hard to recall the shock of pain, the subsequent dull throbbing, the curious sight of the nail later falling off, and the fascination of a new, healthy nail replacing the old one. I wish the sequence could go that smoothly for all children. It doesn't.
In the great flurry of childhood activity (don't you wish you had some of their energy?), smashed fingers and toes are common and memorable events. Whether trapped in doors, banged by hammers, or hit by bricks, some nails re-grow beautifully while others are permanently misshapen.
With most of these accidents, swelling and bruising of the soft tissues and underlying bones are the only injuries. Soaking the finger or toe in cold water immediately after the trauma can reduce both pain and swelling. Acetaminophen or ibuprofen administered right away can also help prevent some of the pain. While taking care of these things (and administering a few hugs and kisses for good measure), you can decide whether or not your child needs to see a doctor.
When to see a doctor:
Sometimes blood collects under the nail -- what we call a subungual hematoma. When handled properly, this does not increase or decrease the odds of the nail healing well. If enough blood is trapped to cause painful throbbing, the nail should be evaluated.
Often the physician will pierce the nail to relieve the pressure. The physician might use a red-hot paper clip, an 18-gauge needle, or an electrocautery machine. While the procedure sounds gruesome (and looks dramatic when the blood starts to spurt from the hole), most children feel great relief and no discomfort. The hot tool glides through the nail like butter.
Fractures of the bone in the fingertip are not common with this type of injury, but need special treatment if they are present. They are considered open fractures (as if the bone had come through the skin) and require treatment with antibiotics. You might suspect a fracture from the force of the blow, the appearance of the finger or toe, a lack of mobility, or persistent pain for more than three days.
As happened with your daughter, the nail will sometimes fall off days or weeks after the injury. What happens when the nail falls off? One group of investigators found that the nail grew back with excellent or very good results in 85% of those studied, with poor results in only 2%. Sometimes the new nail will look different from the original nail no matter what has been done to treat it. But, if the nail is visibly torn at the time of injury, the nail bed might need stitches. Suturing a nail bed that has been torn can dramatically increase the odds of the nail healing well.
The new fingernail will grow at an average of 1 mm per week (0.5-1.2 mm). Toenails grow at one-third to one-half this rate. Overall, four months is the average time for complete re-growth of a fingernail. Re-growth of a nail in a toddler or preschooler may only take a month or two.