Thumb Prosthesis





Introduction: Thumb Prosthesis

This is a high durability, high functionality low cost prosthesis for those missing the distal phalange of the thumb. This creative method can be extended to replace the distal or distal and middle phalange of any finger. The process detailed below is the greatest technological advance in prosthetics since the introduction of modern plastics, and will spark a revolution in the prosthetics industry.

Step 1: Models

I have included two models (free of restriction, share with all of humanity). You can use either model, the claw model is of more utility and can apply greater force than than a natural nail. You can also generate your own models from scratch OR (the most realistic and best fitting) generate a 3D scanned model from a whole digit scan and applying a mirror function to the model.

Step 2: Measurements

Compare digits to find the specific metrics for scaling your model.

Step 3: Measurements

Measure the residual digit (Residuum). Accurate multiple measurements will allow for a greater custom fit.

Step 4: Measurements

Accuracy in measurement is paramount as this prosthesis relies on mechanical fit rather than flexible suction (restricts blood flow and thus wear time) fit.

Step 5: Scale Model

Adjust model to fit residuum metrics acquired above. This is accomplished with modeling software and scaling for length and diameter. Also one should scale areas radially along the vertical axis.

Step 6: Print

PRINT. This prosthesis is most durable when printed in nylon. I suggest that one always use a human friendly plastic for anything contacting the skin. Taulman Nylon 645 is the best material that I found as it has superior strength and quality as well as meeting the EU's REACH standards for non toxicity. Currently there are no suitable FDA approved printing plastics, however that will soon change.

Step 7: Comparison

Compare the printed prosthesis with existing whole digit.

Step 8: Fitted Prosthesis

Check for fit and comfort of wear. You may want to print a model or two at 2-3% larger and smaller due to the mechanical fit and the tendency of the hand to change size during the course of the day. Fortunately this prosthesis is very inexpensive (approximately $1.00 usd in materials) and one can easily have multiple models of varying size and design which will accommodate any person who has fluctuations in the size of their residuum or dexterity/functional requirements.

Step 9: Fitted Prosthesis

Printed Nylon can be dyed with "RIT" brand dye (or any other organic nontoxic dye) to match ones skin color.

Step 10: Fitted Prosthesis

Due to the 3D printing revolution and some advanced materials this prosthesis is the next technological step forward in Prosthetics. It can be fitted to nearly anyone and is ideal for anyone who works with their hands.

Step 11: Price Comparison

This method for creating prosthetic provides significant cost reduction (typically less than 1% ) over traditionally produced prostheses. These Prostheses are ideal for children, the loss prone, the wear prone and those who use their hands for more than clapping. The total cost of creating 3 of these prostheses including materials, modeling time, measuring time and printing time will in general be in the range of $100.00 usd which is less than the average copay/deductible for a standard PVC/Silicone cosmetic prosthesis.

Step 12: Two Thumbs Up

Create and enjoy a new thumb prosthesis using the above methods. This Design and Creative process is provided free of charge and restriction to all of humanity as an act of compassion by the "Laird of Xibalba".




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    60 Discussions

    hey I just found this site and its amazing, I thought my life as I knew it was over but you all have inspired me. I lost my thumb in a CNC machine dual table my glove got caught between the huge tables and the safety mat failed I literally had to tear my thumb off to not lose any other digits so its gone to the palm, ive got to find a way to make the thumb for practical use and recreation such as riding my motorcycle and I was an avid pool shooter and ive tried to hld the stick diff ways even shoot with opposite side ive been going thru the info and its great im 55 and pretty computer savey but idk anything about 3d printers or where to purchase one or what program would be the best for me to start with. any help or suggestions would be so greatly appreciated maybe I can get part of my life back, this depression is horrible , thank you all again

    Is their something like this that I can buy? I have a thumb amputation and could benefit from something like this for typing and other day to day tasks. Let me know when you have the chance. Also, what's the feeling like on the thumb, it is plasticy or does it have the same type of consistency as skin.

    Tim, The Nylon 680 just came out it is the best material now available, easier to work with than 618 and a little firmer

    I should say as well that while the models hold up they are wonderful to wear. It's hard to explain what a strong feeling of balance and utility they give me. I do notice that the surface of the 618 is pretty slippery, and I'm expecting that, as soon as it gets here on Wednesday, a couple coats of Plasti-dip will remedy that, and make the thumb even more useful.


    Thanks, Xi,

    The layers in the models I got yesterday are coming apart after about an hour of wearing them. It seems that just a little lateral flexing does it. I sent my printer the latest specs you posted, and I'll double-check that he's using them and just printing a single layer.

    Any recommendations you can make will be appreciated.


    Tim, sorry I didnt get back sooner. Here are the specs for printing I used on my 2nd gen makerbot.

    normal print speed or slower for better adhesion

    print temp 245 this temp got the best layer adhesion

    1 shell, 0% infill, minimum humidity and dry material

    I am using wings3D its free, I had not used 3d software to any extent and learned it fairly quickly. I found you have to make a print then compare to residuum and adjust thats where the calipers come into play for fine tuning. Tip on the modeling old school, select cross sectional areas of the model and scale, so grab the knuckle section and shrink it a bit you can scale on the x and y independently, then when you get close on the model lay your residuum over the screen image and compare from multiple angles.

    I found when printing multi shell the layers do separate a bit, the material is strong enough in single layer to work.


    The printer showed me several versions of his printouts, but we are finding it difficult to get one to fit securely and for the portion beyond my femaining knuckle to be the right size (that area of the prosthesis tends to be too wide).

    I'm also finding that the layers separate with just a little flexing. Can you recommend a solution to this?

    Lastly, can you recommend an inexpensive CAD software I could pick up to tweak your models? I spent some time learning 3D modeling software a couple of years ago and think I could build some basic proficiency in not too long.

    Thank you.



    I'm going to my printer's tomorrow to try a couple of preliminary
    prostheses he's printed, and I'm pretty excited. I have a few more questions
    I hope you can answer.

    Can you tell me what color or colors of dye you used to color
    your prosthesis? Did you have to mix different colors to match your skin as
    well as you did?

    Do you know of any other way to color the unit besides dye?

    Have you tried spray-painting them, and if so how did that

    My printer tells me the prostheses will be printed in two
    layers. I don't quite understand why or how that is. Can you explain it to me?

    You mention down below that I'll have to trim the base of
    the prosthesis. Would this be a simple matter of a knife and sandpaper?

    I'd like to send you photos of the units we print, if you'd
    be interested. Is there a way we could communicate that's faster than this

    Thank you again for the hope you've provided me.



    Your movable thumb-phalange prosthesis sounds fantastic! Please keep me up to date on your progress.

    About coloring, I'm thinking that I don't want to try to make it blend in. I'm going to try to color it in ways that make it look cool. I forget if I mentioned it, but I'm picking up a couple of cans of spray-on Plasti-dip, and will see if I can apply a colored, tacky-rubbery coating to the thumb pad (the area that you normally would touch things with) that will also add a bit of a cushion to the prosthesis. I may be picking up some draft printouts today. Pretty exciting.

    dclark-craddock, I dont sell these pretty sure I could get in trouble with FDA AMA etc... . Check the thread here, if you have more questions feel free to ask.

    Do you sell these? I recently cut my thumb off at the proximal end (nearest to my hand) but am getting surgery to extend it to about the distal knuckle. Would be nice to have the tip!

    Tim, also the finger does flex it replaces the distal phalange of a finger and it moves the tip like a regular finger does when the middle and proximal phalanges move. Its dynamic. I am working on a prototype that will replace my thumbs phalange with one that moves in a similar fashion. I will have that one up in the future, its way more complicated than the static thumb prosthesis. The dynamic thumb will be awesome, should be able to build in a tactile feed back into the structure. Tactile feed back can be incorporated into the static thumb as well, but again its pretty complicated and I have had to much luck. Any way thanks for the questions, anyone else in the same boat can read all these.

    Tim, I wear all day as the day goes on they get a little looser. I wear in public any time I go out, just for the psycological benefit. Same machine got me as well and no you dont forget that. When your printer gets going try the Taulman 618 and 645 nylons 645 is softer. Once you get a spare for testing they can be died to match skin color be real careful its easy to get them too dark I have light skin it would be alot easier if my skin was darker to color the prosthesis. Also I clean with soap and an electric toothbrush and rinse them with alcohol prior to putting them on, I partially fill with alcohol and put on as Dr. told me to treat residuum with alcohol, this kills two birds. I will get you more info on the dying and surface finish and once you get one i am sure you will find some appropriate customizations.


    I was just looking at your Finger Prosthesis. What is the purpose of all the cutouts and the sort of wraparound straps? Does this thing flex?



    I'm working with a printer in Portland, and he's building a jig for doing a cellphone 3D scan of my unimproved thumb. I'm real optimistic that we'll come up with something good, and will let you know.

    Sweating: yeah I traded deodorant for a daily shower many decades ago. I never liked the idea of clogging up my sweat glands either.

    I'm probably going to print versions of both your straight thumb for bass and the slightly flexed one for piano. how they work in non-musical situations will be a matter of experimentation.

    BTW, How often and how long do you wear yours? Is it an all-day, every day deal?

    And FWIW, My left resid looks very much like your right-hand version. Did you do your like most guys do--with a table saw? That's where mine went. It's not an experience one forgets, is it? I hope I learned something from it--other than "don't stick your hand into a moving saw again."


    Tim, I havent really considered any sort of liner or vent holes. since the prosthetic is hollow through out moisture collects away from my residuum. I have some silicone one they dont ventilate at all, Dr. claims the skin eventually stops sweating but I really dont like that concept. Once you get one made you will see how they work and if it needs improvement for your particular injury. If you get a chance look at thingiverse use this link to see a few more designs I posted," ".

    thanks, Xi.

    Have you ever considered putting some holes in the area below the distal knuckle, for ventilation? Do you think lining the inside with a piece of some kind of open-weave fabric might cushion the residuum and offer some airlfow?

    I suppose it comes down to a balance between stability and ventilation.

    I'm very optimistic about this whole project, and I hope you know how much hope your work is offering. Thank you again for doing this.


    Tim, The model I posted can be altered with 3d software like wings3d. You can select various parts of the model and scale them to fit better. I dont have a high resolution scanner. To get a good fit I visually confirmed the model by comparing my residuum to the visual image of the model in the software, once it was close I printed one then made more adjustments with caliper measurements. It really depends on your software, I am using a very basic one. Having access to a printer is of great help as you will need to make a few to get the fit correct. I find that when printing it is best to have the machine settings set for hollow print single or double walled. As far as the rigidity of the material its fairly soft and should be so its flexible enough to deform while putting it on. One step I find useful is to put the prosthesis in water and heat to boiling for a few minute I include dye at this step, it both colors and softens the nylon. Print the model upright, this allow for a single pass on the model as it prints and leaves a smooth surface both inside and out, rough inside = irritated skin. When it comes of the printer you will have to remove the base and contour the bottom for a better fit. As far as a coating, I haven't tried any yet. I roughen the exterior of the prosthesis to remove some of the nylons slipperiness. I am planning to try a rubber coating on the outside in the near future. I would not recommend coating the inside because of the coating may not be skin friendly an will decrease the interior diameter making it harder to get a god fit. Feel free to ask more questions.


    I've been figuring out how to make my prosthetic, and a thought occurred to me.

    Since one of the things I want to do is to play piano, I've been concerned about hitting the keys with a hard piece of nylon. That would be annoyingly noisy and possibly damaging to the keys. It occurred to me that I could coat the prosthetic with something like Plasti-dip, the stuff people use to coat tool handles with a thin, rubbery coating. I also started wondering if it might be helpful to coat the inside of the prosthetic with that stuff, to cushion my thumb.

    What so you think of these ideas?