Background
In the treatment of the recalcitrant low back pain, lumber interbody fusion (LIF) with titanium cage is commonly performed. Despite the advantage of the titanium cage in biocompatibility and efficiency in restoring the spinal alignment, significant stiffness difference between the titanium cage and adjacent vertebra causes contact stress concentration and shielding, which triggers bone reabsorption and cage subsidence.
Aim
We aim to develop a framework for topological optimised lattice cage with graded-density and young’s modulus to mimic the adjacent vertebral material properties.
Materials and methods
The density distribution of the cage was determined by a multiscale dimensionality reduction optimisation algorithm targeting at minimum stress difference. Re-engineering algorithm was designed to generate the lattice structure pattern. Finite element analysis were utilized to evaluate the performance of the graded-density lattice cage.
Results
Compared to conventional solid cage, the proposed new lattice cage produced smaller stress concentrations and shielding zone in contacting vertebrae.
Discussion and conclusion
This new cage design framework may lead to less possibility of cage subsidence, which reduces the risk of post-LIF implant failure and thus caused revision surgeries. However, empirical and animal experiments need to be done to validate the computerised simulations. The framework can enable direct conversion from personalised clinical data to a physical implant product and generate customized implant design based on individuals’ vertebral properties.