Thumb Prosthesis

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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".

EVERY HUMAN DESERVES TWO GOOD THUMBS.

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    63 Discussions

    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.

    1 reply

    tom 1213 i know how you feel i avoid any hand contact i hide my hand all the time depression is never far away.

    hi i lost the tip of my thumb years ago , i just viewed silicone replacement for the first time i was floored . i was about to pay 800 for one when i came across your site .. im unsure on how to do this but i will try it

    i have just recently lost the end of my thumb in a table saw mishap july 3rd 2018. i cut it off in between the knuckle and start of the nail. i still have much healing to do but this has promted me to finish my 3d printer build. and if you believe it, it has helped me emotionaly as well. i had that digit for 45 years and wasn't quite ready to loose it. anyway i am most definatly going to do this instructable and have already downloaded the stl's. thanks for this

    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

    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.

    Tim

    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

    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.

    Xi:

    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.

    Tim

    Xibalbawax:

    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
    work?

    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
    blog?

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

    Tim

    Xi:

    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.

    Xibalbawax:

    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?

    T

    Xi:

    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."

    T

    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," http://www.thingiverse.com/xibalbawax/designs ".