Embedded Files
Device Components:
Anchor
Plug
Screws
Designing the plug and anchor using Solidworks:
Designing the plug and anchor using Solidworks:
Anchor Design Iterations:
Anchor Design Iterations:
The main goal is to minimize the dimension of the anchor and cut down the material used, so it can fit into the 18mm diameter surgical incision with minimum manufacturing cost. Eventually, two plug holes are added to prevent the plug from rotating or sliding around when attached to the anchor.
Sac/Plug Design Iterations:
Sac/Plug Design Iterations:
From PTFE inflatable sac to PCL molded plug. PCL has low melting point which is a lot easier to shape. We can just melt it by hot water and place it into 3D printed mold. Let it cool down and turn into the desired shape. Non-inflatable design can ensure the surgical process is easy and simple with lower risk of error.
Finite Element Analysis (FEA):
Finite Element Analysis (FEA):
After the design of the anchor and the plug is finalished to an extent, we want to test whether they can withstand the load applied by human interverterbral discs. FEA can analyze the stress (force devided by area) experienced in each location of a component and see whether it will permanently break if exceeding the yield strength of the material used.
FEA on the Anchor:
FEA on the Anchor:
The maximum interdistal force of 400N is applied to the top surface where the plug holes are located, which simulates the force applied by the plug. A fixture is placed at the bottome surface where the screw holes are located, which simulates the reality that the bottome surface will be fixed by the screws
The figure at the left indicates that the stress experienced by the anchor is less than the yield strength of titanium. Hence, it can perform its functional requirements without failure.
The figure at the right indicates that the factor of safety (FOS) is larger than 3, so it can withstand 3 times the force applied. These greatly ensure the reliability and durability of the anchor.
FEA on the Plug:
FEA on the Plug:
The maximum interdistal force of 400N is applied to the surface interfering with the disc, which simulates the force applied by the disc. A fixture is placed at the plug protrusions, which simulates the reality that the protrusions will be fixed by the anchors.
The figure at the left indicates that the stress experienced by the plug is less than the yield strength of PCL. Hence, it can perform its functional requirements without failure.
The figure at the right indicates that the factor of safety (FOS) is larger than 3, so it can withstand 3 times the force applied. These greatly ensure the reliability and durability of the plug.
Physical Testing:
Physical Testing:
After conduting the computational FEA analysis, we want to perform some actual physical testing using Mark-10 loading machine.
4 conditions: herniation + PCL plug, herniation + titanium plug, herniation + PCL plug + resin anchor, herniation only
Applied axial load of 100N and 200N
Measured protrusion length from side + back
Designed fixtures for each of the vertebrae types
Measurements for the control (no device) compared with all treatment conditions
No posterior protrusion was present when using our device
Appears to be a difference in protrusion from the side, but cannot be fully analyzed
Not enough data for statistical conclusion, but show signifant reduce in protrusion when using the device
limitations due to weak spine model and limited budgets
By You-Cheng Lin
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