This project contains the 3D CAD design of a posterior-fixation L1–L2 interbody spinal fusion cage with a rectangular lattice structure for enhanced bone ingrowth.
The design is optimized for additive manufacturing using Ti-6Al-4V ELI titanium alloy (choosen for its unique properties), following general FDA Class II design considerations.
Radiolucent markers are intended to be integrated (not included in the current CAD model) for postoperative X-ray visibility.
- Dimensions: Designed to match L1–L2 lumbar anatomy with a frontal wedge for restoring sagittal balance as well as anti-migration teeth.
- Lattice Structure: Rectangular lattice promotes osseointegration while maintaining structural strength.
- Pore Scaling Concept: Pores are intentionally modeled larger in CAD to represent multiple smaller pores in the manufactured part, or to allow for filling with an osteoinductive gel during surgery.
- Posterior Fixation Compatibility: No screw holes included in the design, as the device is intended to be fixed posteriorly with pedicle screws.
- Chamfered & Filleted Edges: Reduces insertion trauma to surrounding tissue.
- Anti-Migration Teeth: Small, evenly spaced teeth on the top surface prevent implant slippage post-insertion.
- Rounded Corners: Improves patient safety and reduces the risk of localized stress points during implantation.
- Gel Formulation: A theoretical osteoinductive gel formulation for pore filling is described in osteoinductive_gel.md.”
A static stress analysis was performed in Autodesk Fusion 360 to evaluate the implant’s preliminary mechanical performance under physiological loading.
- Material: Ti-6Al-4V ELI (ASTM-compliant)
- Load Case: 1,500 N axial compression applied to the superior surface
- Constraints: Inferior surface fully fixed to simulate contact with the lower vertebra
- Mesh: Default parabolic solid mesh (future work will include refined meshing around lattice struts and anti-migration teeth)
- Max von Mises stress: ~14 MPa
- Max displacement: ~0.001 mm
- Calculated factor of safety: >60 (preliminary — will be updated after mesh refinement and validation)
Note: Current results are from an initial coarse mesh and should be interpreted as a best-case scenario. Further refinement and validation will be performed.
Results showed stress distribution well below the yield strength of Ti-6Al-4V ELI (~830 MPa), with minimal displacement and a factor of safety above 2.0, indicating robust structural performance under typical spinal loading.
This repository includes additional documentation for deeper technical and theoretical details:
- OSTEOINDUCTIVE_GEL.md – Full formulation, rationale, and simulation strategy for the proposed osteoinductive gel upgrade.
- PROJECT_NOTES.md – Expanded design notes, regulatory considerations, and development history for the L1–L2 interbody fusion cage.
- FEA Folder – Contains static stress analysis setup files, simulation results, and supporting images from Fusion 360 for the preliminary mechanical evaluation.
Refer to these files for in-depth information beyond what is summarized in this README.
3D_Models/spinal fusion cage.step— Neutral CAD file for cross-platform CAD software compatibility. This file3D_Models/spinal fusion cage.stl— Mesh file for 3D printing and simulation purposes. This file can be open in any broswers for viewing only purposes.
For educational and research purposes only.
This design is not intended for direct clinical use without regulatory approval, mechanical testing, and biocompatibility validation.
- Integration of radiolucent markers into the CAD model.
- Optimization of lattice geometry for specific mechanical strength targets.
This project is licensed under the MIT License – see the [LICENSE] file for details.