Subsidence reduction effect of transforaminal lumbar interbody fusion (TLIF) with upper and lower open windows modified with lattice structure.

Cage subsidence is a common complication following transforaminal lumbar interbody fusion (TLIF) that can lead to poor clinical outcomes, including recurrent pain and segmental instability. Conventional TLIF cage designs often fail to distribute stress evenly, increasing the risk of endplate damage and subsequent subsidence. This study aims to evaluate the effect of a modified TLIF cage with upper and lower open windows (lattice structure) in reducing cage subsidence in patients with lumbar degenerative disc disease (LDDD). A finite element (FE) model of the lumbar spine was developed and validated. Three TLIF cage designs (Open, Lattice, Closed) were simulated under various loading conditions (flexion-extension, lateral bending, axial rotation), and von Mises stresses were analyzed within the TLIFs, endplates, and cancellous bone. The FE model demonstrated ROMs consistent with cadaveric studies. Elevated stresses were found in all cages, especially Open and Closed designs. The Lattice TLIF showed improved stress distribution, reducing peak stress on endplates. However, increased contact area had a limited effect on reducing subsidence under physiological loads. While contact area alone does not significantly mitigate subsidence risk, incorporating lattice structures may enhance resistance to physiological stress. These findings suggest that optimized TLIF designs integrating lattice structures can improve stability and reduce the likelihood of subsidence, leading to better clinical outcomes (e.g., reduced pain, improved fusion success, long-term stability) in LDDD patients.