The canine nail consists of a central bundle of blood vessels and nerves that are informally known as the “quick,” which is surrounded by a layer of horny material called keratin. The central quick is living tissue, while the brittle keratin is not. Normally, there are five nails on each front foot, and four nails on each rear foot. The front nails that are found slightly higher up the foot are called dew claws.
Nails normally wear down as dogs walk on hard surfaces. However, in dogs that are sedentary or that walk mostly on soft surfaces, the nails tend to grow longer, placing them at greater risk of being cracked or torn. The quick tends to grow out as the nail grows, so injuries often include this living tissue, which accounts for the pain and bleeding.
Nails can become caught on a variety of surfaces, such as floor grates and loosely woven fabrics (eg, afghans). A sudden tug or twist can cause the nail to crack or tear off. Dogs frequently yelp in pain and hold up the injured paw. Any nail can be involved, but those on the front feet are most at risk. The dew claws are especially vulnerable because they are often only loosely attached.
Treatment for a broken nail consists of removing the damaged portion (if necessary), stopping the bleeding, and protecting the damaged area until it heals and new nail regrows. Broken nails need to be trimmed above the break, so that the injury can heal cleanly. This is best done by your veterinarian. However, first-aid procedures at home can help stop the bleeding and protect the foot until you can take your dog to your vet. Ideally, a styptic pencil, silver-nitrate stick, or cauterizing powder can be pressed into the torn end of the nail to stop the bleeding. Alternatively, corn starch or flour can be pressed firmly into the broken end of the nail. Pressure from a folded cloth or paper towel can also stop the bleeding; firm pressure against the wound is needed for at least 5-10 minutes. The foot can then be bandaged temporarily to protect the injured area and to prevent bleeding from starting up again.
Again, because a broken nail is a painful injury, make sure your dog is well controlled for any first-aid procedures. Remember that any animal in pain may bite, so a muzzle may be in order. If you are squeamish or unable to adequately control your dog, it is probably best to simply temporarily bandage the foot with a cloth and take your pet to the vet for immediate treatment. Even with successful first-aid at home, you should have your vet examine the injury within the next few days in case further treatment is needed (eg, in case of infection).
Prevention consists of regular nail trimming and adequate exercise on hard surfaces. Dew claws are often removed at the time of tail docking (for specific breeds) or when the pup is spayed or neutered.