Total and Hidden Blood Loss in Biportal Endoscopic Versus Tubular-Based Minimally Invasive Transforaminal Lumbar Interbody Fusion.

Background: The purpose of this study was to compare total blood loss (TBL) and hidden blood loss (HBL) between biportal endoscopic transforaminal lumbar interbody fusion (BE-TLIF) and tubular-based minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) using hematocrit-based calculations. The study aimed to compare blood loss outcomes between the 2 techniques during their respective initial adoption phases to ensure a fair comparison of hemostatic control. Methods: This retrospective study included 72 patients who underwent single-level lumbar fusion. Thirty-six consecutive BE-TLIF cases (June 2023-July 2025) were compared with 36 early-period MIS-TLIF cases (2016-2021) to ensure comparable learning curve stages. TBL was calculated using Nadler's and Gross's formulas based on hematocrit changes. HBL was derived by subtracting estimated blood loss and drainage from TBL. Results: The BE-TLIF group underwent more additional adjacent-level decompression procedures and longer operative times than the MIS-TLIF group. However, the BE-TLIF group showed consistently lower TBL at the immediate postoperative time point (0.42 vs. 0.62 L, Conclusions: Despite longer operative times and more extensive adjacent-level decompression procedures, BE-TLIF resulted in significantly lower TBL. HBL was comparable between the techniques, indicating that BE-TLIF's hemostatic advantages are achieved through improved intraoperative control. Even during the initial adoption phase, BE-TLIF demonstrated superior hemostatic control.