A Hand Surgeon's Guide to Nail Trauma and Treatment
⌚️ read time: 6.8 minutes
Last week we talked about fingertip injuries in general. But I promised we'd dive deeper into nail injuries specifically. These little joys certainly deserve their own article.
I find nail injuries fascinating. They're incredibly common, yet there's still so much confusion about what to do with them — and what not to. Let's clear that up.
The Anatomy You Need to Know
Before we dive into the injuries, let’s get on the same page about the anatomy. Your nail isn't just the hard part you clip every few weeks. There's actually a complex system under there that's crucial to understand.
I think of the nail as three main parts, as can be seen in the image below as a guide. The actual hard nail is called the nail plate. But underneath that (the pink area you see through your nail) is called the nailbed. Specifically, the pink part is called the sterile matrix of the nailbed. The sterile matrix functions as an adhesive to stick the nail plate down to the finger. When this layer ends, you get liftoff of the nail…and it looks like it turns white. This is the part we trim when we cut our nails.
And the white half-moon shape at the base of your nail? That’s the germinal matrix portion of the nailbed. This is the powerhouse. It's literally the factory (full of stem cells) that produces your nail. Damage this area, and you could have permanent nail problems.
Types of Nail Injuries
Here's where it gets interesting.
Nail injuries typically fall into three main categories, and knowing which one you have makes all the difference in treatment.
Subungual Hematoma
This term is a fancy way of saying "blood under the nail." It usually happens when you smash your finger in a door or accidentally hit it with a hammer. The image below is a good example.
A helpful (though not perfectly accurate) question here is how much of the nail is involved. If it's less than half the nail, it is “acceptable” to do nothing. By acceptable, I mean you have a relatively low (NOT zero) chance of a permanent deformity from what could be an untreated nailbed injury lurking underneath.
When under 50%, it’s also reasonable to have a professional drain the blood by creating a small hole in the nail. This will relieve pressure — and pain.
If it’s more than 50%? You might need the nail removed and repaired.
Nail Bed Lacerations
These are actual cuts in the nailbed. Typically this will be from a cut straight through the nail plate, or again, some sort of smash injury.
The tricky part?
Sometimes you can't even see them until you remove the nail. That’s why the 50% rule introduced above is far less than perfect. But if you've got a large blood collection under the nail and it's painful, there's a good chance you've got a laceration under there. See below for how we decide what to do about these.
Nailbed Avulsion Injuries
These are the nasty ones. Part or all of your nail gets ripped off, which in and of itself is no problem — but it often takes some of the nailbed with it. These almost always benefit from surgery to try to salvage what we can of the nailbed for a reasonable chance of healing. Sometimes we will even borrow nail bed tissue from another finger or toe to fix it (though this sounds better in principle than it is in reality).
The Surgery Decision
Here's something that surprises most people — sometimes what looks terrible won’t benefit much from surgery, and sometimes what looks minor definitely could use the OR.
The biggest factor in this decision?
The germinal matrix. Remember, that's our nail factory. If it's injured, you're almost certain to get a nail deformity. Depending on the severity of injury and your tolerance for a funky nail, surgery may be your best bet.
Even in that case, it’s important to understand that surgery can only decrease, not eliminate, the chance of a nail growing back with a deformity.
The same decision tree exists when we’re dealing with a laceration through the sterile matrix portion of the nailbed. In this case, the severity and likelihood of permanent nailbed injury are just somewhat lower than when we’re dealing with the germinal matrix.
Recovery and Expectations
Regardless of whether you’re dealing with a surgical injury or not, these injuries take time to heal. Your nail grows about 1mm per week, so it'll take 4-6 months for a new nail to grow in completely. It’s not a quick process
The good news? Most nail injuries heal remarkably well if treated properly.
The bad news? You won't know exactly how your nail will look until it grows out completely.
Takeaways:
The size of the blood collection under your nail can be a helpful clue to determine whether you would benefit from surgery
Injury to the germinal matrix (nail growth center) is the biggest concern for long-term nail appearance
Complete nail healing takes 4-6 months, but most people get good results with proper treatment
Looking at your smashed finger and wondering if you need to see someone? When in doubt, get it checked out.
Your future nail will thank you.
