Comparative Analysis Between Single and Double 3-Dimensional Printed Titanium Cages: 1-Year Outcomes After Unilateral Biportal Endoscopic Transforaminal Lumbar Interbody Fusion

Objective: This study aimed to illustrate the techniques of unilateral biportal endoscopic transforaminal lumbar interbody fusion (UBE-TLIF) using double cages and compare surgical outcomes with those using a single cage.Methods: We retrospectively analyzed 62 patients who underwent single-level UBE-TLIF using 3-dimensional (3D)-printed titanium cages (29 with a single cage and 33 with double cages). Radiological parameters, including Bridwell fusion and subsidence grading, were assessed via x-ray and computed tomography at 6 months and 1 year. Clinical outcomes were measured using the visual analogue scale (VAS) for lower back and leg pain, as well as the Oswestry Disability Index (ODI).Results: At the 6-month follow-up, the overall fusion rate (grades I + II) was significantly higher in the double-cage group (86.2% vs. 100%, p=0.04); however, no significant difference was noted at the 1-year follow-up (89.6% vs. 100%). The double-cage group showed lower cage subsidence rates at both follow-ups (3% vs. 31%, p=0.01; 12.1% vs. 38%, p=0.03). The double-cage group exhibited significantly greater improvements in leg pain (VAS: 7.6 to 1.7 vs. 7.2 to 1.4, p=0.03) and ODI (28.6 to 10.8 vs. 28.3 to 9.4, p=0.01) at 1 year.Conclusion: UBE-TLIF with 3D-printed titanium cages achieved a favorable fusion rate at the 1-year follow-up, regardless of whether single or double cages were used. However, double cages accelerated fusion at the 6-month follow-up and significantly reduced cage subsidence at both the 6-month and 1-year follow-ups. These benefits contributed to improved VAS scores for leg pain and ODI at the final follow-up.