A wooden model used to explore the structures of synovial joints, with the knee as an example. Two pieces of wood represent the femur and tibia, with the tubing standing in for cruciate and collateral ligaments and the stretch wrap representing the joint capsule.
Click to enlarge images of students building knees in a first year health science class.
Student Class Exercise
Click on any image to enlarge.
Step 1 - make sure students have all the materials:
- 1 piece of timber with squared off ends
- 1 piece of timber with one rounded end
- 1 roll of stretch wrap
- 4 pieces of tubing (with pre-punched guide holes)
- 8 screws
- 1 screwdriver
Step 2 - Fit the cruciate ligaments
Step 3 - Screw the ligaments down
Step 4 - Create joint capsule by wrapping the joint with stretch wrap
Step 5 - Add the collateral ligaments
- Vinyl tubing - 9mm outer diameter, approx. 200mm long pieces (x4 per set)
- Screws - 25mm long (x8 per set)
- Screwdriver to match screw heads (x1 per set)
- Stretch wrap e.g. 20um thick, 100mm wide roll (x1 per set)
- Pine timber - clean sawn, 90mm x 45mm (or near equivalent)
- Femur - 200mm long with one end shaped into a curve - see photo (x1 per set)
- Tibia - 200mm long (x1 per set)
Using a 10mm drill bit (i.e. wider than the tubing) drill the holes to accommodate the cruciate ligament tubing - just on either side of the middle of the articular faces and at an angle of 45 degrees. A drill press is essential for safety and to keep all parts uniform and interchangeable during class use. Rotate the lower part of the drill press to 45 degrees and make up a jig to hold the work. Make sure that all work is securely held with clamps and ensure that the drill does not penetrate further than is safe. Click on the image to enlarge.
Using a smaller drill bit (diameter to suit the screws) drill guide holes for the cruciate screws - mid-line and about 25mm further away than the large holes. Again, use a jig and a drill press (with the lower part returned to horizontal).
Test the tubing in the cruciate holes and mark where the screw holes should be on the tubing. Multiple tubing pieces can be cut to be 25mm longer at either end and can be pre-punched for the screws.
To mark where the collateral ligament will be screwed down use the tubing holes as a template. Use a jig and a drill press to drill these guide holes in the same position on both sides of the Tibia and Femur.
Once the wooden pieces are satisfactorily shaped and drilled, they should be sanded well and varnished.
Keywords: Teaching, Anatomy, Joints, Science, Biology
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