Controlled versus gravity-based irrigation in endoscopic spine surgery: pressure stability, thresholds, and safety...

Endoscopic spine surgery relies on continuous irrigation to maintain visualization and hemostasis. Gravity-based and improvised high-flow systems may generate unstable or excessive pressures, potentially increasing the risk of neurologic complications. Pump-controlled irrigation offers regulated pressure delivery, but its comparative safety and pressure behavior remain incompletely defined.

To systematically review the literature comparing controlled pump versus gravity-based or high-flow irrigation systems in endoscopic spine surgery, with a focus on pressure dynamics and pressure-related complications.

This systematic review was conducted in accordance with PRISMA 2020 guidelines. PubMed, Embase, Web of Science, and Google Scholar were searched from database inception through January 2026 using predefined search terms related to endoscopic spine surgery, irrigation, and pressure dynamics. Eligible studies included experimental, animal, and clinical investigations reporting irrigation-related pressure measurements (epidural, intradural, intracranial) or pressure-associated complications. Two reviewers independently screened studies, extracted data using a standardized framework, and assessed risk of bias using the Newcastle-Ottawa Scale and MINORS criteria. Due to heterogeneity in study design and outcomes, a qualitative synthesis was performed.

Eleven studies (a retrospective series, cadaveric, and living animal models) met inclusion criteria. Baseline epidural, intradural, and intracranial pressures were low and remained near physiologic ranges during routine operative conditions (approximately 12-18 mmHg). One study found pump-controlled irrigation produced significantly lower working-space pressures compared with gravity-based systems (12.10 ± 3.51 vs 23.86 ± 6.97 mmHg, p = 0.001). Outflow obstruction and dural disruption were consistently identified as primary drivers of pressure escalation. Intracranial pressure remained below 20 mmHg with patent drainage but increased to 86-90 mmHg when outflow occlusion and dural compromise coexisted. One study found symptom onset was associated with pressures exceeding 37 mmHg, with mean symptomatic pressures of 52.9 ± 9.2 mmHg. Neurologic complications, including seizures, were reported in 0.52% of cases and were most frequently associated with impaired drainage and dural violation.

Findings are limited by heterogeneity in study design, pressure measurement techniques, and reliance on observational and experimental data. Direct comparative clinical studies are limited, and publication bias cannot be excluded.

Irrigation during endoscopic spine surgery generally maintains pressures within physiologic ranges under conditions of intact dura and adequate outflow. However, impaired drainage and dural disruption can result in rapid and clinically significant pressure elevations. Pump-controlled irrigation appears to provide more stable pressure profiles than gravity-based systems, though safety is ultimately dependent on maintaining effective outflow. These findings highlight the importance of intraoperative vigilance regarding drainage patency and dural integrity to mitigate neurologic risk.