I have crocheted a bunch of rugs for my Etsy shop, Crochet x Knit, over the past couple of years. Despite performing daily stretch exercises on my arms, I still experienced pain in my right arm to the point where I needed to stop crocheting to allow my arm to heal. One of the issues I had was with the long stem of crochet hooks. I found that the usual stem length was not necessary for crocheting and the stem constantly pressed against the carpal tunnel portion of my hand. I was able to complete the last rug I crocheted, even though I was experiencing mild pain, by wrapping the hook stem with Sculpey clay. It was necessary to stop every other row and adjust the clay, but the rounded shape felt much better in my hand. I designed a crochet hook to mimic the clay and posted the stereolithography file (.stl) file on Thingiverse last year. I made some adjustments to the file and printed it over the weekend.
The handle portion of the hook is designed to fit in your hand so as not to press against the carpal tunnel canal. You can change the hook size by following instructions in the video I made. If you are familiar with Blender, you can also change the shape of the handle to better fit your hand. It is easy to make it shorter once the sections are separated. The link to the file is below, along with a link to an instructional video for changing the size and video transcript.
Link to .stl file. Link to video. Link to video transcript.
UPDATE JULY 5, 2018
The files and videos are no longer available online. The crochet hook can be purchased in my Shapeways shop, Wire Nest, in a variety of colors.