Verification of the Cage Stability and the Superiority of Titanium Coating in the Bone Fusion of Transforaminal Lumbar Interbody Fusion Using Polyetheretherketone Cages.

Objective This study aimed to compare the fusion rate of polyetheretherketone (PEEK) and titanium-coated PEEK (Ti-PEEK) cages in transforaminal lumbar interbody fusion (TLIF). Methods The patient groups that underwent TLIF using PEEK and Ti-PEEK cages were identified and matched for age, sex, and whether the lumbar spine surgery was performed more than once using propensity scores. The rate of three-month postoperative vertebral endplate cyst sign (VECS), which was reported as a predictor of pseudoarthrosis at one year postoperatively, and the one-year and two-year postoperative fusions between the two groups were statistically compared. Results There were 34 patients (12 men and 22 women) in the PEEK group with a mean age of 69.8 ± 8.2 years and 36 intervertebral discs; there were 30 patients (11 men and 19 women) in the Ti-PEEK group with a mean age of 70.3 ± 9.6 years and 36 intervertebral discs. The operated levels were two discs (5.6%) in L2/3, four (11.1%) in L3/4, 21 (58.3%) in L4/5, and nine (25.0%) in L5/S in the PEEK group and were one (2.8%) in L3/4, 24 (66.7%) in L4/5, and 11 (30.6%) in L5/S in the Ti-PEEK group (P = 0.31). The frequencies of positive VECS at three months postoperatively were four discs (11.1%) in the PEEK group and five (13.9%) in the Ti-PEEK group, with no significant difference (P = 0.72). Bone fusion rates at one year and two years postoperatively were 26 (72.2%) and 28 (77.8%), respectively, in the PEEK group, and 28 (77.8%) and 32 (88.9%), respectively, in the Ti-PEEK group, with no statistically significant difference (P = 0.59 at one year and P = 0.21 at two years). Among the five cases of positive VECS in the Ti-PEEK group, two cases (40%) had bone fusion at one year postoperatively around the cage but not through the cage. Conclusion There was no significant difference in the rate of bone fusion or VECS after TLIF between the PEEK and Ti-PEEK groups. Positive VECS is more appropriate for a finding of no bone fusion through the cage at one year postoperatively than for a finding that predicts pseudoarthrosis.