Titanium-coated PEEK versus 3D-printed porous titanium cages in transforaminal lumbar interbody fusion: A meta-analysis.

Abstract

Transforaminal lumbar interbody fusion (TLIF) is a common procedure for degenerative spinal conditions. While polyetheretherketone (PEEK) and titanium (Ti) are established cage materials, titanium-coated PEEK (Ti-PEEK) was developed to combine PEEK's favorable modulus with Ti's osteoconductive surface. This meta-analysis compares the radiographic and clinical outcomes of modern 3D-printed porous titanium (3D-Ti) and Ti-PEEK cages in TLIF. A systematic search of PubMed, Embase, and Google Scholar was conducted up to April 2025 following PRISMA guidelines. Studies comparing 3D-Ti and/or Ti-PEEK cages in TLIF, reporting outcomes of fusion, subsidence, reoperation, or visual analogue scale (VAS) scores with a minimum 6-month follow-up were included. Given the scarcity of direct comparisons, an indirect comparison was performed using single-arm random-effects meta-analyses for each material, followed by meta-regression to estimate differences. Risk of bias was assessed using the Cochrane Risk of Bias tool for RCTs and ROBINS-I for observational studies. Twelve studies (4 RCTs, 8 cohorts) comprising 627 patients and 812 fused levels were included. Single-arm analyses showed high and comparable fusion rates (3D-Ti: 91%, Ti-PEEK: 88%) and similar subsidence (3D-Ti: 19%, Ti-PEEK: 20%) and reoperation rates. Indirect meta-regression found no statistically significant differences between materials for fusion (OR 0.68, 95% CI 0.30-1.50; p = 0.335), subsidence (OR 1.04, 95% CI 0.33-3.22; p = 0.951), reoperation (OR 1.23, 95% CI 0.29-5.24; p = 0.777), or VAS-back (mean difference -0.88, 95% CI -2.49 to 0.73; p = 0.286). Residual heterogeneity was substantial for subsidence (I² = 84%) and VAS-back (I² = 89%), moderate for fusion (I² = 47%), and low for reoperation (I² = 34%). Risk of bias for RCTs was unclear to high (Cochrane RoB), driven primarily by performance bias from unblinded surgeons, and moderate to serious for cohorts (ROBINS-I). This meta-analysis found no significant differences in radiographic or key clinical outcomes between 3D-Ti and Ti-PEEK cages at intermediate-term follow-up. The evidence suggests clinical equivalence, supporting that cage selection can be guided by factors such as surgeon familiarity, cost, and specific patient imaging needs rather than material properties alone.