EE is gaining recognition for effectively treating epidural space pathologies, especially FBSS/PSPS and CLBP linked to radiculopathies or LSS. EE is typically performed using percutaneous access to the epidural space through the sacrococcygeal ligament, utilizing a specialized set of instruments designed for this purpose. This set typically includes an introducer needle, a safety J-guide (Seldinger wire), a dilator, and a sheath. Seldinger technique and a 14-gauge Tuohy needle are used to establish percutaneous access to the epidural space. Once the dilator and guide wire are removed, an endoscope equipped with a video-guided catheter is introduced into the epidural space via the introducer. The video-guided endoscope is carefully maneuvered in a cephalic direction under direct visualization of the epidural space. Fluoroscopic imaging is simultaneously employed to confirm the vertebral level reached by the endoscope tip. To enhance the visual field, the epidural space is irrigated and expanded using saline infusion during the procedure. For epidurolysis, a Fogarty balloon filled with contrast medium is deployed to break down adhesions. Additionally, a surgical lysis of dense epidural scar adhesions is performed using a radiofrequency dissector with a spherical steel tip (0.80 mm diameter, 1 mm working depth). This dissector employs QMR technology to achieve mechanical lysis without causing a significant temperature increase, ensuring precise and safe adhesion management. These instruments are approved through the US Food and Drug Administration (FDA) regulatory process and comply with country-specific medical device regulations or European medical product licensing standards. The surgical technique described is commonly employed in Italy and certain European countries, such as Spain and Germany, but remains less adopted in others. The lack of standardized surgical procedures and instrumentation (also because of limited availability in certain countries) leads to variability in clinical outcomes. Consequently, definitive guidelines for EE have yet to be established.

This Delphi study aimed to obtain expert consensus on 19 statements related to clinical indications, preoperative assessment and management, and technical aspects of performing and reporting EE, in order to identify best practices for EE.

In the field of clinical indications, experts reached consensus on the use of EE for LSS (statement 1, 72% agreement) and FBSS/PSPS (statement 2, 81% agreement). However, no consensus was achieved for its use in disc herniation with radicular pain or radiculopathy (statement 3, 52% agreement). The evidence supporting the use of EE for LSS includes few studies demonstrating significant pain relief and improved outcomes. Specifically, Igarashi et al. [6] found that EE combined with steroid injections provided substantial pain relief in patients with LSS. Lee et al. [35] showed that EE with a Ho-laser (ELND) was effective in alleviating axial LBP, suggesting that patients with LSS with primarily axial LBP might be ideal candidates for ELND. Additionally, Raffaeli et al. [8], using their technique based on radiofrequency/QMR, reported that 67% of patients with LSS experienced overall pain improvement 1 year after EE. Marchesini et al. [36] found EE effective in reducing pain both immediately and 1 month after treatment in patients with FBSS and LSS, although the benefits gradually diminished over 24 months. Additionally, studies have shown that both epidural injections and percutaneous adhesiolysis can effectively provide temporary pain relief in patients with LSS [37,38,39]. Since percutaneous procedures are effective, it is reasonable to assume that the endoscopic approach, which offers direct visualization of the epidural space, would be equally beneficial. In conclusion, EE can be considered a viable intervention for patients with LSS, though further research is needed to confirm its efficacy and establish standardized protocols.

EE has been endorsed with varying levels of recommendation by several guidelines and recommendations for the treatment of FBSS/PSPS [9, 40,41,42,43,44]. In this study, broad consensus was achieved regarding the clinical indications of EE for FBSS/PSPS. However, when the studies were combined, a high degree of variability in outcomes related to pain and disability was reported [41]. This variability may be due to differing techniques (e.g., drug-only treatments versus mechanical/surgical removal of adhesions) or surgical tools (e.g., laser or radiofrequency dissectors), patient characteristics, or type of spinal surgery, with poorer outcomes observed in patients who underwent stabilizing procedures compared to non-stabilizing ones [45], and following lumbar fusion compared to discectomy and laminectomy [46]. Moreover, extensive fibrosis and multiple surgeries further reduce success rates [47], while matching adhesion location to pain source can improve long-term outcomes [48]. Careful patient selection is crucial for optimizing EE success and strengthening the evidence for its use in FBSS/PSPS. Multiple studies have revealed significant heterogeneity in the underlying pain conditions and morphological changes associated with this label [49, 50]. A preoperative endoscopic assessment could potentially optimize the management of FBSS by allowing for more precise characterization of morphological alterations in the epidural space, based on anatomical, morphological, or vasculo-inflammatory findings. For instance, if pain is caused by inflammation and neurochemical changes, treatment may be effective without the need for complete lysis. Conversely, in cases of microfibrosis, it can easily be efficiently removed using a Fogarty balloon catheter.

Although the literature supports the clinical benefits of EE for pain and disability in FBSS/PSPS, more high-quality research is needed because of high variability in study outcomes.

The lack of consensus on the clinical indication of EE for radiculopathies caused by herniated discs is likely due to the small number of studies in the field. Early research reported favorable outcomes in 65% of patients with pain from herniated discs for which traditional discectomy was not indicated or other interventions failed [51]. More recently, Hazer et al. [52] found significant pain and disability improvements, especially in patients not operated on, while others have introduced trans-sacral epiduroscopic laser decompression for lumbar disc herniation, showing promising results [53, 54]. Given the limited evidence, EE for herniated discs should be approached cautiously and reserved for highly selected patients who are not suitable candidates for traditional surgery.

Regarding preoperative assessment and management, experts agreed with the usefulness of lumbosacral spine X-ray or MRI before planning an EE (statement 4, 88% agreement). Given the considerable anatomical variability of the sacral hiatus, including variations in the number of sacral vertebrae, sacral morphology, and other atypical alterations, preoperative imaging is highly beneficial. For instance, MRI can offer critical preoperative insights to help avoid potential complications, such as identifying large or multiple Tarlov cysts [55]. Sekiguchi et al. [56] found that the sacral canal’s diameter averages 6.0 ± 1.9 mm, with some cases measuring less than 2 mm, making 22G needles impractical. Additionally, 3% of sacral hiatuses were closed. Therefore, as it was suggested, precise imaging of sacral morphology is crucial for safe and effective EE [16].

Experts also agreed on the importance of a preoperative anesthetic assessment before EE (statement 5, 76% agreement). As a surgical procedure requiring sedation and anesthesia, EE should always be preceded by this evaluation, which includes identifying drugs that could affect the outcome, such as anticoagulants, and providing an opportunity for informed consent where risks and benefits are discussed with the patient.

Experts agreed that interlaminar access is less safe than sacral access (statement 7, 76% agreement), but no consensus was reached on its use when sacral access is not possible (statement 6, 40% agreement). The interlaminar access presents some safety concerns, as it involves navigating closer to the dura mater, spinal cord, and nerve roots, which increases the risk of accidental dural puncture and nerve injury. In the Avellanal study [23], involving 19 patients with FBSS, only 6 patients (31.6%) experienced significant pain improvement 3 months after the procedure. Six others showed no improvement, while 2 (10.5%) had worsened pain at 6 months. Additionally, 4 patients (21%) experienced dural puncture, and 4 others had transient neurological symptoms, resulting in a 42% overall complication rate, as noted by Fai et al. [57].

Interlaminar access should not be attempted as an alternative to sacral hiatus access, as these approaches are not equivalent. Interlaminar access may be considered only when other approaches are not feasible, and the choice of approach should always be discussed with the patient as part of the informed consent process before EE.

Consensus on the use of epidurography during EE was reached in the second round, with 72% agreement. Epidurography is indeed a valuable tool for evaluating the extent, location, and characteristics of pathological sites prior to initiating the EE procedure. By injecting a contrast medium into the epidural space and using fluoroscopy or computed tomography (CT) imaging, epidurography provides real-time, detailed visualization of the anatomy and precise localization of adhesions as well as their relationship with surrounding structures. This information may help in planning the endoscopic approach. While MRI can broadly observe adhesions, its diagnostic precision is low [58]. In contrast, epidurography offers high diagnostic accuracy by clearly identifying blockages at adhesion sites [59]. However, it is important to note that only direct endoscopic visualization enables the identification of pathological tissues and provides accurate characterization of their morphological and functional features, which cannot be achieved through contrastography or MRI alone [1, 8, 56]. Consequently, performing a lysis procedure based solely on contrast imaging is inadvisable, as it may lead to tissue damage, including the dura, hemangiomas, or other structures as a result of the inability to differentiate tissue types.

Experts broadly agreed on the importance of combining saline infusion and mechanical/surgical lysis of adhesions during EE (statement 9, 96% agreement). Saline infusion is essential for clearing the surgical field of blood and fluids, enhancing the surgeon’s visibility, and distending the epidural space to facilitate instrument maneuverability and improve procedural efficiency. Additionally, it dilutes inflammatory mediators potentially reducing post-procedural pain and inflammation [60]. Mechanical/surgical epidurolysis using specific instruments is crucial for precise and controlled removal of adhesions and scar tissue. These specialized tools potentially enhance the efficacy of the procedure, allowing for better outcomes and shorter procedure times.

In this study, experts agreed that epidural lysis of adhesions with a Racz catheter is not a preparatory procedure for EE (statement 10, 84% agreement). While both epidural lysis of adhesions with a Racz catheter and EE aim to treat epidural adhesions and related pain, they are distinct procedures and are not typically used sequentially. While comparative studies specifically focusing on the effectiveness and complication rates of EE versus the Racz procedure are lacking, some general observations can be made. Both procedures involve similar risks due to accessing the epidural space. However, EE offers the advantage of direct visualization, potentially reducing complications related to instrument misplacement or medication delivery by allowing more accurate targeting of the treatment area. This blind approach makes it challenging to avoid vessel and dura laceration when abnormalities are present in the spinal canal. Additionally, it overlooks the underlying morphology, reducing its effectiveness in accurately identifying the pain-triggering zone and determining the extent of tissue removal [8].

In contrast, the Racz procedure, though lacking direct visualization, is less technically demanding and may be preferred depending on the practitioner’s expertise.

A strong consensus was reached for using local anesthesia with light sedation as the preferred technique for EE (statement 11, 88% agreement) and for the importance of an anesthetic plan that allows detection of alarming symptoms like neck pain, double vision, or headache [59] (statement 12, 92% agreement). Local anesthesia with light sedation is favored because it effectively manages pain at the surgical site while reducing anxiety and discomfort without the risks associated with general anesthesia [61]. Additionally, patients under light sedation remain conscious and can report any unusual sensations [62].

This study found consensus on the practice of injecting medication into the epidural space following EE (statement 13, 72% agreement). Rapčan et al. [47] observed that while both mechanical lysis alone and with added hyaluronidase and corticosteroids improved pain at 6 months in patients with FBSS/PSPS, only the medication group sustained relief at 12 months, indicating a notable benefit of adding drugs to mechanical procedures. However, a systematic review suggested that both epidural saline and steroids with saline have effects beyond placebo and are effective [37]. These findings imply that the primary benefit of EE may come from the mechanical removal and distension of pathological structures, with medication offering additional but not necessarily targeted benefits. Further research is needed to evaluate the effectiveness of medications used during EE compared to other strategies.

Experts agreed in the first round that a dural tear requires immediate interruption of EE (statement 14, 77% agreement). An approach that we believe to be scientifically sound, in light of the results reported by the authors [1], demonstrated that endoscopic exploration of the subdural space during an EE procedure in patients with FBSS/PSPS has never led to the identification of pathological findings such as adhesive arachnoiditis or reactive fibrosis in the subdural compartment. This was observed even when severe fibrotic pathology was identified in the posterior epidural space during the same endoscopy. Therefore, continuing the exploration after creating damage to the dura would only risk placing the instrumentation in the subdural space, potentially harming the arachnoid or nerve roots, without offering any diagnostic or therapeutic benefit.

A dural tear, or dural puncture, is a serious complication that necessitates stopping the procedure to manage the tear and prevent severe consequences [63]. If a tear is detected, the procedure should be paused to evaluate the dural lesion and the patient’s symptoms (e.g., headache, nausea, clear fluid leakage). Management includes stopping further manipulation, attempting to seal the tear, and positioning the patient in a supine position to reduce cerebrospinal fluid leakage. The decision of whether to resume the procedure depends on clinical judgment and the patient’s stability.

Consensus on the maximum volume of saline infusion during EE was reached only in the second round (statement 15, 84% agreement). High infusion rates during EE can increase epidural pressure, potentially injuring tissues or causing severe complications like optic nerve compression, which could lead to vision problems or blindness [64]. To mitigate these risks, an international consensus recommended limiting the infusion volume to 200 ml per procedure [65]. Most panelists (65.4%) adhere to this limit, considering it relatively safe. However, the literature shows significant variability in the volumes used, ranging from 120 to 650 ml [20] and up to 1200 ml [66] without detecting higher percentage of complications compared to literature findings. Factors such as infusion rate, volume, fluid leakage, and epidural space compliance affect epidural pressure, making precise pressure control challenging [67].

Regarding the technical aspects of reporting EE, experts agreed on the importance of documenting hyperemia grading and describing its characteristics, such as arterial or venous ectasia, blood flow interruption during structure stretching, and neoangiogenesis, at the end of the procedure (statement 16, 84% agreement). Hyperemia provides valuable information about the local tissue response, potential inflammation, or injury, and is observed in epiduroscopic images as areas of increased blood flow in the dura root sleeve, peridural membrane, or other epidural structures compared to normal areas [68].

Grading hyperemia helps assess the tissue response, with mild hyperemia potentially indicating a normal reaction and severe hyperemia suggesting significant inflammation or complications. This information can guide post-procedural management, such as the need for anti-inflammatory medications or adjustments in patient activity. Documenting hyperemia grading also provides a baseline for future follow-ups. A strong consensus was also reached on the importance of reporting the severity of epidural fibrosis using validated scales (statement 17, 96% agreement). Epidural fibrosis, caused by excessive fibroblast proliferation around the nerve root, can impact post-procedural management and the need for additional interventions [69]. Documenting fibrosis severity at the end of EE helps guide treatment decisions and ensures consistent assessments, improving communication among clinicians. An example of a grading system is the one proposed by Bosscher and Heavner [58]: grade 1 represents loose strings and sheets of fibrosis; grade 2 consists of more organized, continuous fibrous material, not resistant to the endoscope; grade 3 involves dense fibrous material, where the endoscope can only be advanced with difficulty; and grade 4 consists of dense fibrous material, where the endoscope cannot be advanced.

Raffaelli and colleagues [1, 8] classified fibrotic conditions on the basis of both macroscopic characteristics, identifying four subgroups of fibrosis, and functional characteristics, specifically functional/dynamic instability secondary to compartmental fibrosis that exerts traction on the dura. In the state of “dynamic instability,” pathological fibrotic structures adhere to the dura, restricting its natural ability to respond to physiological stimuli. This leads to the dura becoming essentially “frozen,” losing its elasticity and mobility. Any applied force, such as traction or compression, is then transmitted further, potentially affecting perineural structures, interfering with nerve root nutrition and blood supply, and causing pain. This condition may be exacerbated by local vascular stasis, hyperemia, and aseptic inflammation due to fibrous tissue bridging around vessels.

A detailed report at the end of EE should include the extent, location, and any related findings such as nerve root compression or vascular involvement. Whenever possible, images or videos of the fibrosis should be attached for future reference.

Consensus was reached on the importance of reporting the presence or absence of allodynia after balloon catheter opening during EE (statement 18, 73% agreement). Allodynia in this context is likely caused by mechanical, inflammatory, and sensitization factors affecting nerves and surrounding tissues. Raffaeli et al. [1] defined this condition as a “compartmental syndrome,” similar to complex regional pain syndrome (CRPS).

This consideration regarding a possible resemblance to CRPS is based on clinical and anatomical findings observed during EE. However, the intent is not to equate the two conditions but to describe a “CRPS-like pattern” observed in specific cases characterized by hyperaemia, hypervascularization, and dura mater sensitivity in the absence of adhesive fibrosis. This distinction aims to establish a framework for classifying epidural findings and enhancing the consistency of terminology in clinical practice. Nevertheless, dedicated studies are needed to further investigate this phenomenon, clarify its underlying mechanisms, and validate this suggestion.

Patients should be informed about the possibility of temporary pain sensitivity post-procedure as part of the healing process.

Additionally, full consensus was obtained on the importance of accurately describing the technique used for EE (statement 19, 100% agreement). Precise documentation is crucial for maintaining a comprehensive medical history, guiding future treatments, ensuring legal compliance, and adhering to medical standards.