The document describes a study that tested various clavicle fracture fixation devices under torsion and bending loads. The objectives were to compare the mechanical strength, stiffness, and failure modes of different plate designs. Devices from Synthes and DePuy were tested, including dynamic compression plates, locking plates, and a pin. Results showed differences in torsional strength and stiffness between devices, as well as differences in failure mechanisms. Calculated torque values based on plate geometry and material properties were generally consistent with experimental torque measurements at yield, though assumptions introduce some error.

1. TORSION TESTING
Biomechanical Testing of Fracture Fixation Devices

2. Torsional fractures

3. Case Study: Biomechanical Testing of
Clavicle Fracture Fixation Devices
• Treatment for clavicle fractures:
• Conservative (sling and rest)
• Non-conservative (surgery w/plate or pin)
• When is surgery necessary?
• Shortening of more than 2 cm
• Comminuted
• If nonunion occurs
• Difficult for surgeons to determine appropriate
fixation configuration

4. Objectives of Study
• Compare the strength and stiffness of fracture fixation
devices used to treat clavicle fractures
• Determine mode of failure of devices in torsion and
bending
• Calculate amount of elastic and plastic deformation in
torsion and bending
• Provide mechanical data to help clarify and inform clinical
practice and experience

5. Synthes® 2.7 mm DC
• Dynamic Compression
• 2.7 mm thick
• Thinnest of all plates
• Easily bent into shape during
surgery
• Low profile

6. Synthes® 3.5 mm LCDC
• 3.5 mm thick
• Limited Contact Dynamic
Compression (LCDC)
• Bent into shape during
surgery

7. Synthes® 3.5 mm Locking LCDC
• 3.5 mm thick
• Locking Limited Contact
Dynamic Compression
• Locks screw to plate
• Bent in to shape during
surgery
www.synthes-stratec.com

8. Locking compression plates allow better
reduction of displaced fractures

9. Synthes® 3.5mm Reconstruction and
Curved Reconstruction Plates
• Reconstruction plate (left)
is manufactured straight
and bent into shape during
surgery
• Curved Reconstruction
plate (right) is
manufactured with a curve

10. DePuy® Active Compression Plate
(ACP)
• Dynamic compression
• Titanium
• Very biocompatible
• More difficult to bend into shape
during surgery
www.jnjgateway.com

11. DePuy® Rockwood Clavicle Pin
• Improved blood supply to
bone
• No bulky hardware
• Easier to remove
• Smaller incision required

12. Method of Testing: Torsion
• Record load (Nm) vs. position (deg)
• Elastic range (osteotomy and
segmental defect):
• Rotate 10 degrees at 5 deg/sec
• Measure stiffness (Nm/deg)
• Test to failure (segmental defect):
• Rotate to failure, 5 deg/sec
• Measure load and displacement at yield
and failure points

13. Sample Torsion Test Results

14. • Boxes with the same color are not significantly differently (p<0.05)
• Dotted line = solid composite clavicle
Results: Torsion, Elastic Range

15. Torsion - Yield
Boxes with the same color are not significantly differently (p<0.05).
* Indicates construct failure without plastic deformation in some or all
samples.

16. Results: Torsion to failure
• Torsion failure without plastic deformation (Ti ACP, 3.5 DC,
and 3.5 LDC)

17. Results: Torsion to failure
• Torsion failure with plastic deformation (2.7 DC, 3.5
Crecon, 3.5 Recon, and Pin)

18. Deformation Due to Torque
• For a structural member under torsion, its cross section
will rotate at angle 
• Non-circular cross-sections will warp (transverse sections
don’t remain plane, they twist)
• If warping is unconstrained, torque can be calculated:
’= T / GJ  T = GJ ’
• T = Torque
• G = shear modulus
• J = Polar moment of inertia; units = length4
• ’ = Angle of rotation per unit length, /L (1st derivative of 
wrt to z-axis); units = rad/length (rad/mm, rad/inch, etc.)

19. Question: How well do calculated and experimental values for
applied torque compare for bone plates tested in torsion?
• Given data for bone plate materials and designs, and
formula for torque in non-circular cross-sections, estimate
the torque applied to each bone plate (load at yield)
• Hint: Use the angular deformation at the limit of elastic zone, and
estimate length over which deformation occurs from plate geometry
•
• How do your calculations match up with the experimental
data provided? What are some sources of error?
•
• Draw sketches as needed, and justify your answer by
supporting it with facts.

20. What do we need to know to answer the question:
How well do calculated and experimental values for applied
torque compare for bone plates tested in torsion?
• Note: Approximate width of
bone plates is reduced by
about 2 mm for recon plates