Purpose: Compared to titanium cage, polyetheretherketone (PEEK) cage with pedicle screw fixation has been increasingly used in transforaminal lumbar interbody fusion (TLIF). However, there is insufficient evidence supporting the superiority of PEEK cages over titanium cages as optimal TLIF spacers. The aim of this study was to compare the clinical and radiographic outcomes of patients at a 2-year follow-up after undergoing instrumented TLIF in which either a PEEK cage or a titanium cage was implanted.
Materials and methods: We retrospectively analyzed prospectively collected 48 patients who underwent single-level TLIF in which the first 23 patients received a titanium cage and the 25 patients received a PEEK cage. Patient demographics, clinical outcomes, and radiographic imaging were studied.
Results: Improvement of clinical outcomes was comparable between the two groups. Based on the criteria using computed tomography, 96 % in the Titanium group and 64 % in the PEEK group showed fusion at 12 months. At 24 months, fusion rate in the Titanium group was increased to 100 %, while PEEK group showed 76 % of fusion rate. In the PEEK group, vertebral osteolysis was noted in 60 % of the cases with nonunion. This abnormal finding was not observed in the Titanium group. Vertebral osteolysis was significantly associated with nonunion.
Conclusions: The superiority of PEEK cages over titanium cages for bony fusion was not demonstrated. Additionally, we found unfavorable radiographic findings in the cases with a PEEK cage, which may lead to nonunion. Improvement in biocompatibility of a PEEK cage will be needed to increase the fusion rate.