The pelvis is composed of three bones that have fused together: the ilium, the ischium and the pubis. This project will bind together the primary joints that interface with the pelvis::
- Sacroiliac Joints
- Pubic symphysis
This will be slightly more difficult than assembling the jaw just due to the number of holes to be drilled, particularly for the SI joint. If you have any questions, please don't hesitate to drop them in the comments below.
Adapting the Skeleton
1. Drill Holes for the SI Joint
Begin by drilling 4 holes in each joint surface to secure the ilia to the sacrum. As you can tell from my example below, this required a few trial runs at first. It may be helpful to drill to holes in the ilium, then place it on the sacrum and use a felt tip pen to mark where the holes should be on the sacrum.
2. Join the ilia and the sacrum
The bones can then be secured together using 1/8'' bungee cords. Cut four 8'' sections of cord and use two on each side to join the surfaces flush together. Adjust the tension to allow stability with a slight amount of movement.
For clarification, refer to the video at the bottom of the post.
3. Prep the Pubic Symphysis Disc
Drill a hole through the center of the disc included with model. This will be used to secure it in place later
4. Drill three holes through each of the pubic bones as shown here.
5. Bind the bones together
Using three 1/8'' cords, tightly bind the pubic bones together.
6. Put the disc in place
Thread a 1/16'' cord through the disc (shown here in red). Pull the bones apart and wedge the disc between. Tie the small cord around the larger bungee cords to secure the disc within the joint.
7. Bore out the femoral head
Drill a hole large enough for a 1/4'' cord through the head of the femur as shown here.
To expand the range of motion in the hip, bore out the corridor where the femur meets the acetabulum so that the cord won't get pinched as the femur rolls within the socket.
Cut an 8'' section of 1/4'' cord, tie a knot in one end and thread the other through the femur.
8. Bore out the acetabulum
Drill a 1/4'' hole through the deepest part of the acetabulum. Thread the cord from the femur through it and tie it off on the other side.
9. Tie the left and right hip cords together
Examining the Model
So how does this look in real life? In the video below I walk through these three joints.
This represents a substantial improvement over most everything that you'll find out there.
For the next stage of the project, move down to assembling the knee.
"Gray241" by Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body; Bartleby.com: Gray's Anatomy, Plate 241. Licensed under Public Domain via Wikimedia Commons