Abstract
We have thoroughly studied the systematic review and meta-analysis titled “Uniportal Versus Biportal Endoscopic Decompression for the Treatment of Lumbar Spinal Stenosis” by Lobo et al published in the Global Spine Journal. 1 The authors conducted a systematic comparison of clinical outcomes between uniportal and biportal endoscopic decompression techniques for lumbar spinal stenosis, following the PRISMA guidelines. The research design is rigorous and the analysis is meticulous, providing high-quality evidence of significant reference value for current endoscopic spinal surgical techniques. We fully acknowledge the high-quality work of the authors.
While affirming the overall academic value of the study, we wish to contribute a supplementary discussion regarding the methodology used in calculating and interpreting perioperative blood loss. This aims to further refine our understanding of the “minimally invasive” nature of endoscopic spinal surgery.
This study primarily employs intraoperative blood loss as the key indicator to evaluate perioperative blood loss. However, in endoscopic spinal surgery, continuous saline irrigation is a standard procedure, which significantly dilutes intraoperative bleeding. Consequently, intraoperative blood loss, as estimated by suction volume or surgeon assessment, may not fully reflect the patient’s actual blood loss burden. Previous studies have introduced the concept of hidden blood loss (HBL), describing blood loss components not directly observed during surgery, including blood loss into tissues, hemolysis, and dilutional effects of fluids. HBL has been demonstrated to hold significant clinical importance in various orthopedic and spinal surgeries. 2
Recent studies on minimally invasive and endoscopic spine surgery indicate that HBL accounts for a substantial proportion of total perioperative blood loss—often 40%–70%—and its absolute volume is frequently significantly higher than the intraoperatively visible blood loss. For example, Wen et al, in a study on minimally invasive transforaminal lumbar interbody fusion, estimated total blood volume using the Nadler formula and calculated total blood loss via the Gross formula. Their findings showed that even with low intraoperative blood loss, HBL constituted a major component of perioperative blood loss and was statistically significant. 3 This result suggests that relying solely on intraoperative blood loss may systematically underestimate the true blood loss burden in minimally invasive or endoscopic surgery.
Similar phenomena have been observed in studies related to biportal endoscopic spine surgery (BESS). Peng et al compared blood loss between BESS and open lumbar surgery, revealing that although intraoperative blood loss was significantly lower in the BESS group, the difference in total perioperative blood loss became considerably smaller when HBL was included. Moreover, HBL remained a high proportion of total blood loss, showing statistically significant differences between groups. 4 This finding further indicates that intraoperative blood loss alone does not adequately represent the overall hematologic impact of endoscopic surgery on the body.
Furthermore, HBL has demonstrated value in differentiating between different endoscopic decompression techniques. Zhou et al, comparing unilateral biportal endoscopic decompression with interlaminar uniportal endoscopic decompression, found that while intraoperative blood loss was low and not significantly different between the two techniques, the perioperative decline in hemoglobin or hematocrit levels showed significant differences. Consequently, the calculated HBL volume demonstrated statistically significant differences between groups. 5 This outcome suggests that variations in muscle dissection, bone removal techniques, and the use of energy devices among different endoscopic approaches may manifest more in “invisible blood loss” rather than being fully captured by intraoperative blood loss records.
Therefore, when interpreting the finding of “no significant difference in intraoperative blood loss between uniportal and biportal endoscopic decompression,” it is crucial to recognize that this conclusion primarily reflects visible intraoperative blood loss and may not represent the true total perioperative blood loss burden. We believe that future studies, where feasible, incorporating hematological parameters to assess HBL or total blood loss would enhance comparability across studies and provide a more objective and comprehensive evaluation of the minimally invasive advantages of different endoscopic decompression techniques.
We once again express our gratitude to the authors for providing this high-quality research contribution to the field and thank the editorial team for facilitating valuable academic exchange within spinal surgery.
Footnotes
Author Contributions
Bin Liu: Writing – review & editing, Writing – original draft, Methodology, Conceptualization.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.
Statement
During the preparation of this work the author used ChatGPT in order to Improve the language of the manuscript. After using this tool, the author reviewed and edited the content as needed and takes full responsibility for the content of the published article.