A Commentary on “Comparative Outcomes of Biportal Endoscopic Decompression, Conventional Subtotal Laminectomy, and Minimally Invasive Transforaminal Lumbar Interbody Fusion for Lumbar Central Stenosis”

Xiangge Liu

doi:10.14245/ns.2551030.515

To the editor,

I wish to convey my sincere admiration for the authors’ excellent work presented in the article “Comparative Outcomes of Biportal Endoscopic Decompression, Conventional Subtotal Laminectomy, and Minimally Invasive Transforaminal Lumbar Interbody Fusion for Lumbar Central Stenosis [1].” This rigorously conducted retrospective cohort study provides valuable evidence by comparing perioperative, clinical, and radiological outcomes of 3 widely used surgical approaches, thereby addressing a long-standing clinical question in the management of lumbar central stenosis. The comprehensive analysis and clinically relevant findings make this study an important contribution to the ongoing efforts to optimize surgical strategies in this field. With great respect for the authors’ work, I would like to offer a single methodological suggestion specifically regarding the evaluation of blood loss, which may further enhance the robustness of future research.

The article reports that the estimated blood loss (EBL) in the ULBD-UBE (unilateral laminectomy bilateral decompression with unilateral biportal endoscopy) group was significantly lower than that in the subtotal laminectomy and MIS-TLIF (minimally invasive transforaminal lumbar interbody fusion) groups (65.6±82.3 mL vs. 118.8±73.4 mL and 192.9±145.8 mL, respectively; p<0.001). However, it is important to recognize a key characteristic of endoscopic procedures: the need for continuous and copious saline irrigation to maintain a clear operative field. The suctioned intraoperative fluid inevitably contains large volumes of irrigation solution, resulting in substantial dilution of blood and leading to an underestimation of true blood loss when using EBL. It is worth noting that this principle also applies to full-endoscopic spine surgery, even though the amount of irrigation fluid used is relatively lower; during the initial phase of the learning curve, when operative times may be prolonged, similar dilution effects can likewise influence the assessment of blood loss. This methodological limitation can therefore bias the assessment of intraoperative bleeding in favor of endoscopic techniques [2-4].

To address this statistical and methodological limitation, several recent studies on endoscopic spine surgery have adopted the Gross method, which indirectly estimates total blood loss (TBL) using preoperative and postoperative hemoglobin concentrations (or combinations of hemoglobin and hematocrit) [5]. While both open and endoscopic procedures underestimate actual blood loss compared to the Gross method, the degree of underestimation differs markedly. For open surgery, intraoperative EBL accounts for approximately 56.7% of TBL [6], whereas for UBE procedures it accounts for only 16.6% [7]. Thus, using TBL calculations based on hemoglobin changes provides a more equitable comparison of the true overall blood loss associated with different surgical strategies.

Therefore, we respectfully suggest that future research designs and reports on blood loss in spinal endoscopic surgery consider including the following elements: (1) simultaneous recording of preoperative and postoperative (within 48 hours) hemoglobin and hematocrit values; (2) estimation of individual patient blood volume using established formulas, followed by calculation of TBL based on hemoglobin changes; (3) avoidance of exclusive reliance on intraoperative EBL when analyzing blood-loss-related outcomes, instead adopting TBL as the primary comparative metric.

Such measures would not only enhance the scientific rigor and comparability of data but also allow for a more accurate reflection of the true perioperative safety differences between endoscopic and conventional surgical techniques. We believe that as endoscopic techniques become increasingly widespread and research in this field deepens, standardizing and optimizing blood loss measurement methodologies will be critical for improving the quality of evidence in spine surgery. Nonetheless, it should be noted that the timing of postoperative blood sampling is critical, as hemoglobin and hematocrit levels may not decrease immediately after surgery, and that intraoperative or postoperative transfusions—more common in multilevel open procedures—can also confound the accuracy of this method.

Finally, we would like to once again thank the authors for their valuable contribution to the field of spinal surgery and the editorial team for providing this platform for academic discussion.