Hidden and total perioperative blood loss in unilateral biportal endoscopic lumbar interbody fusion (UBE-LIF) versus endoscopic lumbar interbody fusion (Endo-LIF) for two-level degenerative lumbar disease: a retrospective cohort study

This study aimed to compare the perioperative blood loss profiles of unilateral biportal endoscopic lumbar interbody fusion (UBE-LIF) and uniportal full-endoscopic lumbar interbody fusion (Endo-LIF) in patients with two-level degenerative lumbar disease and to identify risk factors associated with blood loss to support the optimization of procedure selection and perioperative blood management. This retrospective cohort study included 114 patients who underwent two-level endoscopic lumbar fusion between June 2023 and December 2024 (65 in the UBE-LIF group and 49 in the Endo-LIF group). Perioperative total blood loss (TBL), hidden blood loss (HBL) derived from the Gross formula, hemoglobin (HGB), hematocrit (HCT), and other relevant variables were recorded. Univariate and multivariate linear regression analyses were used to assess the effects of body mass index (BMI), operative time, and the use of bone cement–augmented pedicle screws (screw tract augmentation) on perioperative blood loss. There were no significant differences in the baseline characteristics between the two groups (P > 0.05). The UBE-LIF group, however, had significantly greater TBL (1.08 ± 0.46 L vs. 0.81 ± 0.51 L, P = 0.004) and HBL (851.86 ± 431.76 mL vs. 626.77 ± 467.43 mL, P = 0.009) than did the Endo-LIF group. Multivariate linear regression revealed that surgical technique (UBE-LIF), longer operative time, and lower BMI were independent risk factors for increased TBL and HBL (P < 0.01). Each additional minute of operative time was associated with a mean increase of 0.002 L in TBL and 1.629 mL in HBL. Pedicle screw augmentation was a protective factor and significantly reduced blood loss (TBL: β = − 0.211, P = 0.014; HBL: β = − 0.217, P = 0.013). Subgroup analyses further revealed that (1) screw tract augmentation significantly reduced blood loss only in the UBE-LIF subgroup (P = 0.029); (2) differences in blood loss between UBE-LIF and Endo-LIF were statistically significant only in patients with a BMI ≥ 24 kg/m2 (P < 0.01); and (3) prolonged operative time was significantly associated with increased blood loss only in the Endo-LIF subgroup (P < 0.05). Compared with Endo-LIF, UBE-LIF results in greater perioperative blood loss in two-level endoscopic lumbar fusion. Prolonged operative time and lower BMI independently predict increased blood loss, whereas screw augmentation mitigates bleeding, particularly in UBE-LIF. Among patients with BMI ≥ 24 kg/m2, Endo-LIF appears preferable for limiting blood loss. Procedural planning should therefore incorporate BMI, anticipated operative duration, and the intended use of screw-tract augmentation to optimize perioperative blood management.