Subsidence after L5-S1 transforaminal lumbar interbody fusion using 3D-printed porous titanium interbody cage: A single-institution retrospective study

<subsection>Aim:</subsection>Transforaminal lumbar interbody fusion (TLIF) of the L5–S1 segment of the spine is technically challenging and has higher cage subsidence rates compared with other lumbar levels. Because three-dimensional–printed porous titanium cages (3D-PTCs) exhibit superior bone integration and elastic modulus closer to bone compared with polyetheretherketone (PEEK) cages, we hypothesized they might reduce subsidence. This study examined subsidence rates, reoperations, and risk factors in patients who underwent L5–S1 TLIF using 3D-PTCs.<part /><subsection>Material and Methods:</subsection>Patients who underwent L5–S1 TLIF using 3D-PTCs between 2019 and 2020 were retrospectively reviewed. Demographic and surgical data were collected. Cage subsidence was graded using the Marchi classification on postoperative radiographs and computed tomography scans. Logistic regression analyses were performed to identify independent risk factors.<part /><subsection>Results:</subsection>A total of 89 patients were included in the study. The overall subsidence rate was 23.5%, with 8.9% classified as severe (grade II or III). Multivariate analysis identified smaller cage cross-sectional areas, lower Hounsfield unit values, more vertical cage positioning, and intraoperative endplate damage as significant predictors of severe subsidence (all p < 0.05). Three patients (3.4%) required a second operation for symptomatic subsidence.<part /><subsection>Conclusion:</subsection>Subsidence rates following TLIF using 3D-PTCs were comparable to those previously reported for PEEK cages. Poor bone quality, cage size and orientation, and endplate integrity were important predictors of subsidence. Further prospective studies are needed to assess the long-term benefits of 3D-PTCs in L5–S1 fusion surgery.

spinal fusion porous titanium polyetheretherketone