Having once again reawakened a back injury from long ago, I figured these were good for some comic relief:
The full-scale L4-L5 vertebrae are from Printables and the ¾ scale L5 is from somewhere I cannot recall. A mother lode of anatomical models is on Thingiverse if you want some 3D printing challenges.
The L4-L5 pair are part of an extensive human anatomic model locating all the pieces at their proper coordinates, so these two hovered about 800 mm above the XY plane. I ran them through the Grid:Tool mesh editor to center them at the XY origin, then put the bottom-most point at Z=0.
Rotating them individually in PrusaSlicer and painting only the most essential support got them to this state:
Each one take about three hours, so I ran them individually to reduce surface blemishes and maximize the likelihood of happy outcomes. Worked like a champ.
The retina-burn orange disk is not anatomically correct, because the InterWebz apparently does not have a model for spinal cartilage:
Instead, it’s a rounded cylinder resized into an oval, with its top and bottom surfaces formed by subtracting the vertebrae:
The OpenSCAD code doing the heavy lifting:
// Disk between L4 and L5 vertebrae
// Ed Nisley - KE4ZNU
// 2025-03-07
Layout = "Show"; // [Show,Build]
include <BOSL2/std.scad>
module Disk() {
color("Red")
difference() {
translate([9,-18,36])
rotate(110)
resize([33,45])
cyl(d=50,h=14,$fn=48,rounding=7,anchor=BOTTOM);
import("../Spine/human-spinal-column-including-cervical-thoracic-and-lumbar-vertebra-model_files/L4 L5 vertebrae stacked.stl",
convexity=10);
}
}
if (Layout == "Show") {
Disk();
color("White",0.3)
import("../Spine/human-spinal-column-including-cervical-thoracic-and-lumbar-vertebra-model_files/L4 L5 vertebrae stacked.stl",
convexity=10);
}
if (Layout == "Build") {
Disk();
}
All of the magic numbers come from eyeballometric measurement & successive approximation.
The Build layout left the disk floating in space, whereupon I used PrusaSlicer to reorient it edge-downward on the platform with painted-on support for minimal distortion:
Two dots of E6000+ adhesive hold everything together.
All in all, it was a useful distraction. I’ve been vertically polarized for the last five days and it’s good to be … back.
The Smell of Molten Projects in the Morning 
Comments
3 responses to “Human Lumbar Vertebrae”
When I saw the thumbnail for this post, and given the recent post about bad naming conventions on your MRI disk, I assumed these were 3D prints of your bones. If one is interested, there are ways to extract the DICOM data from your MRI disk and create a 3D model of your own bones that you can then export/slice/print.
Color me interested! Tell me more …
AFAICT from the Weasis displays, the slice resolution is around 5 mm, so the models would be chunky. But it’d definitely make for a much more interesting desk ornament. :grin:
For Windows machines, visit http://www.slicer.org for the software. There’s a bit of a learning curve, but not impossible… I also referenced this PDF https://spujol.github.io/SlicerVisualizationTutorial/SlicerVisualizationTutorial_SoniaPujol.pdf It’s for an older version, but you will be able to figure out most of the differences fairly easily. This page: https://training.slicer.org/#segmentation-tutorials also has some good information.
I found that for my pelvic area CT Scan that the software “made up” for the relatively thick slices by interpolating (for my CT scan, it was ~3.0 mm front to back, ~0.8 mm top to bottom, and ~0.8 left to right). The pelvis I printed (admittedly at 10% size) looks remarkably like the plastic skeletons that doctors sometimes have in their offices.