Multicenter Cohort Validation of Endoscopic Dual-Zone Decompression for Lumbar Spinal Stenosis: A Comprehensive Assessment of Perioperative Hidden Trauma and Hidden Blood Loss

<title>Abstract</title> <p>Background Traditional assessments of minimally invasive spine surgery (MISS) often rely on superficial metrics like incision length and overt blood loss (OBL), neglecting systemic stress and hidden blood loss (HBL). Objective To evaluate the perioperative hidden trauma, muscle injury, and HBL of endoscopic dual-zone decompression (DZD) compared with transforaminal lumbar interbody fusion (TLIF) in elderly patients with degenerative lumbar spinal stenosis (DLSS). Methods A retrospective, multicenter cohort study was conducted on 432 elderly patients with DLSS from January 2024 to December 2025. Patients were divided into the DZD group (n = 220) and the TLIF group (n = 212). Propensity matching verified homogeneous baselines across 12 variables (P &gt; 0.10). Total blood loss (TBL) and HBL were derived utilizing the Nadler and Gross equations. Systemic inflammatory dynamics (Interleukin-6 [IL-6], Tumor Necrosis Factor-α [TNF-α]) and multifidus muscle damage (Creatine Kinase [CK]) were tracked longitudinally at preoperative (T0), postoperative 24h (T1), 72h (T2), and 7 days (T3). Results OBL was significantly lower in the DZD group than in the TLIF group (45.2 ± 12.4 mL vs. 412.8 ± 85.4 mL, P &lt; 0.001). However, HBL accounted for 79.31 ± 6.42% of TBL in the DZD group, which was significantly higher than the 53.33 ± 5.18% observed in the TLIF group (P &lt; 0.001). Repeated-measures ANOVA revealed significant group × time interaction effects for IL-6, TNF-α, and CK (P &lt; 0.001). Serum CK in the DZD group experienced a mild elevation at T1 (124.2 ± 32.5 U/L) and completely reverted to baseline at T3 (86.2 ± 15.4 U/L), whereas the TLIF group exhibited severe, prolonged muscle destruction (P &lt; 0.001). Conclusion Although endoscopic DZD demonstrates a paradoxically higher proportion of hidden blood loss due to hydrostatic containment intraoperatively, it significantly mitigates systemic inflammatory responses and preserves the structural integrity of the posterior tension band compared to open surgery.</p>