I broke my wrist, so instead of sweating inside a plaster cast for six weeks I
decided to spend the time building a breathable, 3D-printable one.
Input a video of an arm on a table → out comes a printable cast.
It’s a thumb-spica cast, the kind used for a scaphoid wrist fracture. This is
an early prototype and not a medical device.
How It Works
Video of arm
→
Arm meshphotogrammetry
→
Arm + hand keypoints
→
Generate cast
→
Print
What It Does
Builds a clean, watertight model of the arm to wrap
the wrist, thumb and knuckles are found automatically
Wraps it in an offset shell
covers the forearm and wrist, wraps the thumb with the tip exposed, leaves the four fingers free
Uses a “forgiving” cradle design
a rigid wrist + thumb core where immobilization matters
an open forearm cradle cinched by velcro straps, so it’s adjustable and tolerant of error
Cuts a self-supporting lattice
a diamond pattern for breathability and weight, oriented so it FDM-prints with no support material
Is tuned for the printer
a solid print base / spine over the thumb column
strap slots cut square to the surface with self-supporting pointed ends
an optional pass that rounds sharp edges so nothing digs into skin
Outputs a watertight STL ready to drop into a slicer