IT WAS DEWCLAW WEEK

This little piggy’s got it all

This time it’s all about the toes and nails……

FROM MIC A WIKIPEDIA USER WITH SERIOUS SHUTTERBUG SKILLZ

FROM MIC A WIKIPEDIA USER WITH SERIOUS SHUTTERBUG SKILLZ

Well, you brought us some interesting cases this week for sure! This week at South Park’s Woof and Purr Vet we treated a lot of patients with dewclaw problems. There was a young active dog with a dislocated dewclaw of unknown origin (possibly play-related). There were also painful infections of the nailbeds in one older dog’s paws, including her dewclaws. Another dog tore off the nail of one of his dewclaws. Fluffy long fur likes to hide overgrown dewclaws which will then “avulse” after getting caught up on brambles, furniture, just about anything and then get separated as the dog tries to free himself. One dog had overgrown misshapen dewclaws which then excoriated the skin, nearly penetrated it and caused secondary infection.

FROM MILLER'S ANATOMY OF THE DOG AND CAT

FROM MILLER’S ANATOMY OF THE DOG AND CAT

Lastly, we’ve been seeing a patient recently with some irritation and scarring where dewclaws were removed. The associated carpus (wrist in humans) is very arthritic and we are concerned about his comfort. After so many years we don’t know how they looked when he was young and if he’s suffered very long like this but we intend to help him. Seeing dewclaw disease is pretty common in veterinary practices because dewclaw disease is pretty common, but it was a banner week for healing the dewclaw at Woof and Purr Vet and we had our work cut out for us!

Well, if dewclaws seem to cause so much misery, Jayme, why do dogs and cats even have them? Do they serve a useful purpose or are they vestigal from eons and species past and now just a pain in the…. paw? Since they all seem to have the little buggers or have had them removed, what can we do to protect them? Why do some breeders or breed clubs recommend removing them while others insist the dog has them? What does Woof and Purr Vet, as a practice, think about the value of the dewclaw? Could it help a pet to keep a close eye on those silly & questionable toes? Please let’s find some reason not to just wish they’d disappear.

ANATOMY and bit of PHYSIOLOGY and a dash of GENETICS but lite, promise

The dewclaw is a toe (digit) consisting of a metacarpal bone (in the case of the forelimb and when compared to your hand this is the bone between the base of your thumb and your wrist) which is similarly attached at the base to the dog or cat’s leg near the wrist. By following along the metacarpal bone away from the wrist you can feel it then attaches to one of the two dewclaw “phalanges” (bones – this one analagous to the longer bone of your thumb) and then that connect to the other at the tip of your thumb. The bone (phalanx) at the end also grows the claw like yours grows a nail…. well, hopefully. This forelimb dewclaw is consistently found in canids including the domestic dog, the wolf and the jackal and all cats, large and small. You can   find it in some birds and reptiles too. The nail (or claw) at the tip is a continuously-growing keratin topping produced by the living nail bed beneath which is present at the tip this distal phalanx and tightly connected to the nail it forms.

Thanks+ASPCA

THANKS ASPCA

But where the nail itself is not alive, can’t experience pain or bleed, the nail bed source, is rich in vessels and nerve endings. That vascular and sensitive nail bed tissue sometimes makes nail trims an olympic sport. Particularly in dogs, the nail (or claw) color is usually consistent with the fur color at the tip of the toe so dark toes have dark nails and light toes have light nails (great for finding the quicks) and many dogs with multiple toe fur colors can have multiple nail colors even on the same foot. The proximal attachments (from the dewclaw’s bones to the limb higher up) can include a small bone called the sesamoid and multiple tendons tethering to muscles in the “forearm” (fancy doctor word would be antebrachium but whateva). Everything in the forelimb dewclaw, like everything in your thumb, is alive except the nail and the superficial layers of skin.

The dewclaw is a digit (digit 1 in fact) on the inside of the leg & usually found a bit higher than the the other toes. Therefore, whereas digits 2, 3, 4 and 5 (anatomists count from the inside of the leg making digit 5 the last or “pinky toe” on the outside edge) touch the ground in normal paw configuration this dewclaw digit does not. That makes it a non-weight-bearing digit and that seems to be where many problems come in. The dewclaw doesn’t sit right next to all the other digits and can be a bit of an overlooked orphan in the paw maintenance and care realm. It doesn’t touch the ground (or always the scratch post as the case may be) in the normal paw and therefore it doesn’t easily wear down naturally like the other claws of the forefeet in pets with normal feet. That can lead to the claw overgrowing as it ducks under the radar during a toenail trim (Woof and Purr Vet trivia: our shorthand for that is TNT) or being silently problematic since pain in that toe doesn’t easily lead to lameness.

The front dewclaw to cats and dogs is anatomically what the thumb is to us. But, functionally in the vast majority of cats and dogs there is much less usefulness. Though the occasional cat (especially polydactyly cats with the Hemingway mutation) or dexterous dog may find use when climbing, turning sharply or holding a chewy morsel, these front digits rarely have the degree of strength or conscious control to give a vast amount of benefit to the regular pet. Hunting cats may use this digit and be less effective without it.  Hunting dogs may have owners who remove them just for that bramble laceration injury problem we mentioned earlier.

Whether or not agility dogs without them are at a disadvantage is a HOTLY contested debate among veterinary anatomists and agility trainers worldwide. There’s mounting evidence that they may stabilize the canine carpus (wrist joint), contact the ground when running at high speeds or even be used as a defense weapon & that’s an interesting potential vote promoting leaving them in place unless they pose an actual threat to the pet (keep getting caught on things, get a tumor, bone infection, etc). A couple of cases have brought the higher likelihood of wrist arthritis in dogs with amputated fore dewclaws to the table. In general, dogs and cats always have forelimb dewclaws and sometimes have trouble with disease in them or have them removed.

not+that+Sonic

Conversely, hindlimb dewclaw genetics are not as straightforward. The LMB1 protein, when mutated, alters the regulation of the sonic hedgehog gene and occasionally out pops some hindlimb dewclaws. Some breeds have them reliably and doubly. Trivia for the old school gamers out there: a scientist responsible for finding and therefore rewarded with naming one of the genes involved in limb and digit formation and as a result for promoting dewclaw growth chose “Sonic Hedgehog” after a comic his daughter had based on the Sega early 90’s game’s character coincided with similar genes being named for “real” Indian and desert hedgehogs. Of course we scientists are sticks in the mud and the “the” had to go but the early game reference is forever.

Anyhoo, hindlimb dewclaws usually result from a mutated gene (no offense to the mutants) so in this case the dewclaws are more about mutation than garden-variety growth and typical dog anatomy. Exceptions do exist as do multiple hindlimd dewclaws usually with one stalk and two toe tips. Some breed standards actually require them and if lacking double hind dewclaws the Great Pyrenees and Briard are faulted in the show ring. As is frequently the case (shout out to sickle cell heterozygotes avoiding malaria), “mutant” is in the eye of the beholder. So, generally vets don’t fret about removing those since their functionality is not so controversial. Random side note, my cat actually has fully articulated (bone-attached) hind dewclaws which is SUPER RARE – so I love this topic!

So, are you saying “remove them”?

I think removing bits and pieces of living tissue without solid evidence of any benefit in doing that is more than odd and worrisome at the least and very risky and painful at worst. Therefore, fore dewclaw removal is less controversial and not generally considered at Woof and Purr Vet. Though many of our patients come to their forever homes with the “tails and dewclaws” procedure performed as neonates and so were already altered as pups or prior adoption, we don’t perform that surgery on pups or declaw cats so we don’t have to debate the merits of that here. What we do recommend is meeting with us and having a consultation if you are considering removing hind dewclaws or just have questions or concerns about your pet’s dewclaws. Those hindlimb dewclaws are generally useless tags of skin with a bit of nail that flop around and are without any bony attachment. No bony attachment means they are harder for the pet to guard as they don’t lie flat and easier to get caught up and torn. Those do seem prone to all sorts of trauma and needless worry. We’re not opposed to considering that procedure and would be happy to discuss the merits of your pet having them removed.

Are they ever something I want to have around if I don’t have vermin or go hunting or do competitive agility? Could they help me or my companion animal out? Anything Jayme, please…?

YES, all the nails like all the skin (and the mouth and eyes) are a convenient set of windows to allow a peek into your pet’s total health. They aren’t just scratchy tipped decorations to be trimmed that occasionally need to be treated. They provide owners and their veterinarians a non-invasive and simple indication of the health of the animal’s insides too. Bringing an abnormal nail to our attention (dewclaw or not) doesn’t mean your animal will be diagnosed with a serious disease. Most nail problems are simple and easy to solve problems. But, an abnormal nail you find could help us get a head start in diagnosing serious medical issues. Early diagnosis can benefit you and your pet by controlling cost and minimizing discomfort rather than waiting for problems to worsen if treatments aren’t started as soon as possible to slow the disease. So, of course preventing and treating painful conditions localized to nails are valid and important reasons to keep an eye on those toes, but there are even more important clues you want to pick up on. Then we can help you protect the health of your dogs and cats & make the best care affordable.

So, which diseases show signs in nails and toes?

Diseases with broad implications throughout the body that can show initial signs in the nails or toes include:

  • cancers (melanoma, squamous cell carcinoma, lung-digit syndrome)
  • immune-mediated & inflammatory diseases (lupus, pemphigus, vasculitis, arthritis)
  • clotting abnormalities (thromboembolism)
  • allergies (food & environmental)
  • bacterial/fungal/viral/parasitic infections (bone infections, tick-borne disease, Leishmaniasis, cryptococcosis, distemper, cutaneous horns with FIV, ear or skin mites, hookworm)
  • hormonal diseases (hypothyroidism, Cushings, diabetes)
  • toxic, nutritional & genetic defects

For the average pet with normal intact fore dewclaws, we do have some basic reminders

Inspect toes, pads & all claws, fore + hind, at least once a month looking for:

  1. pain or tenderness
  2. swelling or asymmetric size (it’s easier to note when comparing to two sides)
  3. redness of the surrounding skin
  4. discharge- moist or crusty brown
  5. overly long nail – we’d rather see a half-moon shape than a fully formed C, we can trim those puppies for ya
  6. missing, torn, separating or broken nail
  7. thickened, peeling, flaking, discolored nail or a nail with distorted direction of growth
  8. abnormal position – should lie along the length of the leg, not stick out towards midline

Paws up on nail health for all the pets!!!

And for all my team (including our newest member as of today: Kesia) great job this week on the paw x-rays, pain management, clipping/cleaning, numbing, cauterizing, medicating, bandaging and TNTs!!!! I saw your patience and gentle manner with the pets and I know they appreciated it too.

Last helpful hint from your friendly miniature vet: try to touch those tootsies every day, folks. If every time someone touched your feet it ended up with your nails being trimmed without your permission you’d be more likely to resist it too. A regular paw massage at home from mom or dad makes nail trims easy-breezy beautiful.