3D Printed Orthotic Shoes for a Tiny Dog

This is Lucifur (the Lord of Barkness). She is my best friend, partner in crime, and constant companion. I’ve had her for 11 years, since I first got her at just 9 months old. She was supposed to be a foster but once I saw that derpy smile, I knew she was already home. We’ve been everywhere together and gone on so many adventures together! In fact, if you look through my past Instructables, you’ll see we’ve made some pretty awesome stuff together.

What’s not awesome are her feet. They're pretty f*cked up. She has degenerative arthritis which causes them to splay out. It also makes them ache constantly. Even barely touching them makes them hurt and walking long distances is agony. To help alleviate the pain our vet suggested orthotic carpal braces. Unfortunately, to get custom fit ones, those damn things are $800. Per. Foot. That's $1600 for both her front feet. This is a pandemic. Ain't nobody got money like that right now. Time to DIY this project!

I did a ton of research online looking at different models of braces and I think we’ll be able to make a fairly decent replica using my Anet A6 3D printer.

First thing we need to do is gather supplies. I used:

• 1 Chihuahua
• Dremel with sanding barrel
• Vaseline
• Quick set alginate for molding
• Paper cups for mixing
• Mixing spoon or popsicle stick
• Casting plaster
• 2-part silicone molding putty
• STL files
• 3D printer with PLA filament
• Editing program (optional – I used Fusion 360)
• Slicing program (I really like Cura)
• Craft foam
• Hook and loop Velcro tape
• Thread
• Needle
• Hot glue
• Superglue
• Lots of dog treats and cuddles

First thing I need to do is prep Lucifur’s paws. As you can see in the picture of her feet, the nails are really long. Because she has arthritis, she doesn’t do a ton of running around outside so the nails don’t naturally grind down as my other dogs do. Now before anyone wonders why I’m hanging my dog off the back of my closet door, let me reassure you that this is completely comfortable for her and she’s totally relaxed. The harness she’s hanging in is actually a front-facing doggy bag that we use in the winter to carry her around in (it fits under my jacket so she stays nice and toasty) so she’s used to it.

I gently grind her nails down using a Dremel on the lowest setting and a sanding barrel. This thing is ancient and the battery only lasts about 5 minutes and it rotates at half speed even when you have it pushed all the way to high...but for her it worked great! There are pet-specific grinders out there that I strongly suggest if you don’t happen to have an old half-assed Dremel. Using a full speed Dremel can cause friction burns and injure tender paws, so be careful!

Luci doesn’t mind this method at all, but if you’re planning on using it with your dogs, go slow so they can get used to the sensation and the noise. Regardless, it’s much easier on Luci and my sanity than clipping using clippers (ugh…that was the WORST!)

Because I want her boots to fit perfectly, I’m going to cast her paws in plaster. I’m starting with her right paw first. Once her nails are nice and short, I make sure to grease up her paw with Vaseline to prevent the alginate from sticking to it. Then I mix up the alginate according to the manufacturer’s directions. It starts pink and as it cures, it turns white.

I carefully hold Lucifur's very well-greased paw in the alginate. She has to hold still for ten minutes.I sing to her as we wait to help keep her entertained. She's so patient...but clearly not impressed with my singing. You can see the alginate turning from pink to white in the photos.

Once the alginate sets, I can carefully pull her paw out. As you can see, there’s a paw-shaped hole in the alginate!

I turn the mold upside down to drain out the excess water and then fill the cavity with plaster. Once the plaster sets, I have a perfect cast of her tiny paw. Looks good!

As you can see, the cast of her paw looks like a normal paw. That’s because when we took the mold, she was hanging up and her paw was relaxed and didn’t have any weight on it. This is how I’d like her paw to look all the time.

To see the contrast between her paw at rest and when it’s weight-bearing, I made a second mold using a non-toxic two-part silicone molding putty. I mix up two equal balls of the putty mix, blending them until they’re one light purple color and then roll it into a ball.

I gently set Lucifur down on that ball and have her stand there with her full weight until it sets. Clearly Luci isn't nearly as fond of this technique as she was of yesterday's milkshake mold. But she's such a good dog and so patient.

Just hold still, Luci... All molded!

Time to add some plaster.

I molded the same paw (right front side) so you can see the difference between what it looks like when she's standing and when she's hanging up.

And here you can see the side by side. On the right is her paw cast from hanging on the door. You can see how although it's still somewhat splayed out, it's more "normal" to what a paw looks like. On the left is her paw with all her weight on it. Poor thing looks like a pancake.

Because the majority of her pain when walking comes from her foot splaying out and the muscles stretching, I wanted to make sure the bottom of her bootie helped cup her paw into a more natural "paw" shape.

Having it in plaster also made it easier to mold the bootie to her foot without burning her as I have to heat up the PLA to make it fit right.

Now to make the orthotic splint to help hold her foot in the normal “paw” shape.

A few weeks ago I found an STL file on Thingiverse.com that user XZBC511 made for his cat and it looked like it was almost perfect for Luci!

STL file here: https://www.thingiverse.com/thing:1935961

2 hours and 49 minutes later...I had a printed PLA splint (under proper supervision, of course)!

Because I want the splint to be comfortable, that means I need to pad it. I trace the splint out on soft foam that I will use to line the bootie for comfort. Because both her front paws are bad, I cut out two foam liners.

Next, I need to make sure the splint is molded to Luci's foot. PLA filament softens in boiling water and you can easily mold it to whatever shape you need and then let it cool and it will hold the shape.

I need to form it around her paw for a custom fit but I don't want to burn her...time for her stunt paw!

I form the softened PLA around the plaster mold, making sure it hugs her smooshy toes without pinching them or digging into her paw pads.

Although Luci is not super heavy (she’s about 9 lbs) just the fact that she’ll be walking on these booties will put stress on the PLA. To help give it a bit of strength, I reinforced the area where I bent it up to make the ‘L’ shape by adding a few drops of superglue to weld the edges of the plastic together. I also gave it a coating of hot glue under the foam to give it a bit more structure as well. This is critical if you decide to do this project sized up for a larger dog. In fact, for anything more than 15 lbs, I would strongly suggest either fiberglass or resin support to help augment the PLA and provide the stiffness and strength it needs to give your puppers (or kitty or whatever you use this on) the structural support to make this splint work properly.

Back to our build. Luci has stubby legs so I trim off the top of the splint and sand down the edges so they're smooth and rounded. Here's the finished molded splint shell!

To keep the splint in place on her foot I carefully sewed on some Velcro straps.

Then, using a little hot glue, I carefully lined the bootie with the soft craft foam. I even put a foam pad on the bottom to help give her some traction (the PLA is really slippery on hard surfaces without this!)

You can see how the finished splint looks here!

It's so itty bitty! Aww!

Time to see how it fits!

MUCH BETTER! As you can see, they hold her little paws in a more natural "paw" shape and her footies are much less "pancake." You can see from how her paw looks that the cupped bottom fits perfectly. It helps hold her toes in position and gives her wrist stability which helps prevent her from rolling her joint out when she walks or runs.

So stylish! I might have to paint her toenails to match. Happy puppy! One paw down...one to go.

Because both her front paws are bad, I repeated the steps above to create a second bootie. Then, to make sure they work well for her, I took her outside for a little testing.

Based on watching her walk, I realized that the first iteration was too tall in the back and she was having trouble bending her legs properly. While I thought it would help support her, in actuality it hindered her...and since my number one goal with this project is to make her life better, that meant having to go back to the drawing board for some reworking.

I did some snipping and sizing and realized if we took off about an inch, they would be the right height.

Rather than print the entire splint again and then cut the tops off and waste all that PLA, I ran the STL file through Fusion 360 and used it to chop off about half the height in the back of the splint. Now, more properly sized to Luci's stubby little legs, I printed two more splints.

Then it was just a matter of repeating all the steps I did yesterday to make two identical but shorter splint boots.

Well Luci...how do they feel? You think you can walk in them?

They work! She walked all the way across the dining room without stumbling once!

I can tell they're not 100% perfect but as far as a proof of concept goes, I'm ecstatic! There are obviously some refinements that need to be made (and professional vetting, of course) but she made it all the way across the room without tripping once! GOOD GIRL. And yes, I'm well aware I sound like an idiot. Please, ignore my voice and just focus in on the adorable dogs (cameo by Pandamonium, Lucifur's younger but much denser sister.)

Now before we wrap up this post, there are a few last little things we want to say before we sign off.

1. I'm not a vet. I'm a marketing monkey at a small start-up that helps brands protect themselves from counterfeits. It's about as sexy as a cabbage. That being said, I have NO illusions about being qualified to make these shoes as anything more than a prototype which is why I am taking them to my actual trained vet for a professional opinion before these shoes become a permanent part of Luci's daily wardrobe.

2. Even if these shoes are fully approved by our vet, they are meant to be worn when we go walking and are outside...when she's inside and on the carpet, she's happy just being herself. These shoes are not for full-time wear.

Take good care of your furry babies and always make sure whatever you're making for them, it makes their lives better...not worse. :)