The Pelvis and Hip

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::

  1. Sacroiliac Joints
  2. Pubic symphysis
  3. Hips

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. 

Note how wide the exit of the drill hole is.

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. 

Alternatively, you can just fuse the joints together and pretend they aren't there.

Alternatively, you can just fuse the joints together and pretend they aren't there.

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.

Image

"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