Abstract
Background: Biportal endoscopic transforaminal lumbar interbody fusion (BESS-TLIF) is an emerging minimally invasive technique. This study aimed to evaluate the two-year radiological fusion outcomes of single-level BESS-TLIF using a specific banana-shaped, porous titanium interbody cage. Methods: This retrospective study reviewed 51 patients who underwent the specified procedure. The primary endpoint was the radiological fusion rate, assessed by computed tomography (CT) over 24 months using a three-grade system. Factors influencing fusion, particularly bone graft composition (demineralized bone matrix [DBM] only vs. DBM with I-factor), were also analyzed. Results: The final complete fusion rate at two years was 96.1% (49/51; 95% Confidence Interval (CI), 86.5-99.5%). Bony fusion occurred predominantly in the posterior and intracage regions. The only significant factor influencing fusion was the bone graft material. The 'DBM with I-factor' group achieved complete fusion significantly faster than the 'DBM only' group (log-rank test, p < 0.001), with a higher final fusion rate (100% vs. 83.3%, p = 0.045). Conclusions: Single-level BESS-TLIF using a banana-shaped, porous titanium cage provides favourable two-year radiological fusion rates. The selective addition of I-factor as an osteoinductive supplement can significantly accelerate the time to achieve solid arthrodesis.