Lumbar Epidural Adhesions
Epidural fibrosis is thought to be one potential cause of failed back surgery cases, but can also occur in non-surgical cases. This article explores epidurolysis of adhesions, a procedure designed to treat chronic pain originating from these and other conditions.
Scarring Triangle
The concept and name "Scarring Triangle" was developed by Dr Gabor Racz. he recognition of this space came from the difficulty of threading a catheter from the sacral hiatus to the ventral aspect of the L5 nerve root. The space is underneath the "armpit" of the L5 nerve root and lateral to the S1 nerve root, and located above the level of the L5/S1 disc not below it. This is a uniform space with a small volume, averaging between 0.9 to 1.1 mL. It collects all the wast material and forms dense hard scar tissue.
Pathophysiology
A common misconception is that epidural adhesions, which are abnormal unions of membrane surfaces due to inflammation or injury, are themselves direct pain generators. For a structure to generate pain, it must have a neural supply. The pain associated with these conditions, particularly radicular (nerve root) pain, is produced by the movement or irritation of nerve roots that are already swollen and inflamed.
Normal, healthy nerve roots do not cause pain when moved. However, scar tissue can encase a nerve root, fixing it in one position. This makes the nerve root highly susceptible to tension or compression during movement, which in turn causes pain. This fixation is a central premise behind the procedure.
Epidural fibrosis can result from both surgical and non-surgical causes. Post-surgical scarring is common after procedures like laminectomy or fusion, with excessive scarring increasing the rate of recurrent radicular pain. Non-surgical causes include annular tears, hematomas, and infections, all of which trigger an inflammatory cascade leading to fibrosis. This inflammation is driven by high concentrations of inflammatory agents like phospholipase A2, which can be thousands of times higher in herniated or degenerative discs.
The formation of dense scar tissue in the Scarring Triangle is an important reason for the failure of surgeries and other procedures. It can lead to failed minimally invasive surgeries that focus on the lateral recess, and failed spinal fusions.
Clinical Features
Apart from the usual assessment for patients with chronic pain originating from the lumbar spine, there is a provocative test called "Dural tug." The patient is made to sit up wiht a straight leg, bend forward until their back pain is elicited. The patients head is then rapidly passively flexed. This stretches the dura cephalad and if adhered to the posterior longitudinal ligament it will elicit pain at the site of adhesions.
How Epidurolysis Works
Epidurolysis is a medical procedure aimed at disrupting scar tissue and freeing spinal nerve roots within the epidural space. This allows for the site-specific delivery of medication to the area of pathology and pain generation, helping to reduce swelling and inflammation and restore mobility and function.
The procedure is known by several synonymous terms in medical literature, including: Epidural neuroplasty, neurolysis, epidural adhesiolysis, percutaneous adhesiolysis.
The core goal of epidurolysis is to utilize a catheter for the targeted injection of fluids and medications, opening the perineural space around an affected nerve root to alleviate pain and improve function. It is the fluid that does the dissection not the catheter itself.
The mechanisms of action in epidurolysis are multifaceted and work together to achieve pain relief:
- Hydraulic: The volume and pressure of the injected fluid mechanically breaks up adhesions, freeing the entrapped nerve root.
- Chemical: Specific medications are used to reduce inflammation, dissolve fibrotic tissue, and block pain signals.
- Mechanical: While the catheter is guided to the target area, aggressive mechanical disruption is avoided to prevent injury or a subdural injection.
Clinical Evidence and Efficacy
The effectiveness of epidurolysis is supported by decades of research. Initial studies demonstrated that a one-day procedure was as safe and effective as the traditional three-day hospital stay, providing significant, stepwise pain relief with repeat procedures.
Subsequent randomised controlled trials confirmed these findings, showing that adhesiolysis with hyaluronidase and hypertonic saline provided statistically significant improvements in pain relief, disability index scores, and range of motion compared to injections of local anesthetic and steroid alone.
The strongest evidence is from a large sham controlled randomised controlled trial that followed patients up for 10 years, showing stable persistent benefits over sham.[1]
Long-term Efficacy of Percutaneous Epidural Neurolysis of Adhesions in Chronic Lumbar Radicular Pain: 10 Year Follow-up of a Randomized Controlled Trial
| Exposure group outcome (EGO) = a / EG | 0.935 |
|---|---|
| Comparison group outcome (CGO) = c / CG | 0.692 |
| Relative Risk (RR) = EGO / CGO | 1.351 (95% CI 1.029 to 1.774) |
| Risk Difference (RD) = EGO ā CGO | 0.243 |
| Number Needed to Treat/Harm = 1 / |RD| | NNT 4 |
| ā | |
| Treatment risk (EGO shown above) | 93.5% |
| Control risk (CGO shown above) | 69.2% |
| Absolute risk reduction (ARR) = CGO ā EGO | -24.3% (95% CI -44.1% to -4.6%) |
| Relative risk reduction (RRR) = 1 ā RR | -35.1% |
Key Medications Used in the Procedure
Several key medications are employed during epidurolysis to ensure its effectiveness.
- Hyaluronidase: This enzyme helps facilitate the spread of other medications by breaking down connective tissue. It reduces neutrophil infiltration, the first step in the inflammatory process, thereby decreasing swelling and pain. Its use has been shown to reduce the treatment failure rates.
- Hypertonic Saline: This concentrated salt solution is believed to help reduce nerve root edema. Studies have shown that patients treated with hypertonic saline required fewer additional treatments compared to control groups. It may be administered in a series of three repeated injections to maximise the effect on fibroblasts.
- Local Anesthetic and Steroids: These medications, such as bupivacaine and triamcinolone, are delivered directly to the site of inflammation to provide immediate pain relief and reduce swelling. The triamcinolone may be delivered through the neural foramen of the affected nerve root to improve success.
- Contrast Dye: An imaging agent (e.g., Omnipaque) is used under live fluoroscopy to visualize the epidural space, identify filling defects caused by scar tissue, and ensure the proper placement and spread of medications.
The Epidurolysis Procedure
The most common indication is for ongoing axial pain or radiculopathy secondary to postsurgical epidural fibrosis. The procedure is performed with the patient awake to provide real-time feedback, typically using only oral sedatives.
Caudal Technique:
- Accessing the Epidural Space: The physician gains access to the epidural space, most commonly via the caudal approach through the sacral hiatus. The needle is inserted, and its position is confirmed.
- Epidurogram: 5-10 mL of contrast dye is injected to perform an epidurogram. This initial injection helps confirm correct placement and identifies filling defects, which are areas where the dye cannot spread due to scar tissue. This step is critical for correlating the location of the fibrosis with the patient's reported pain.
- Catheter Placement: A steerable catheter is bent slightly at the tip and advanced under fluoroscopic guidance toward the targeted filling defect, aiming for the ventrolateral epidural space where pathology often occurs. The catheter tip is positioned at the site of nerve root compression or irritation.
- Injecting Medications: Once the catheter is in place, the following injections are made sequentially, with aspiration and contrast checks between each step:
- Hyaluronidase (e.g., 150 units of Hylenex) is injected to begin breaking down the scar tissue and facilitate the spread of subsequent medications.
- Local anesthetic and a steroid (e.g., bupivacaine and triamcinolone) are injected to reduce inflammation and pain.
- Hypertonic saline (10%) may be slowly injected to reduce oedema.
- Confirmation and Neural Flossing: The physician confirms that the injections have opened up the scarred area, observing contrast "runoff" or spread into the previously blocked region. Patients are then instructed on neural flossing exercises, which are gentle movements designed to keep the nerve root mobile and prevent new adhesions from forming.
Trans S1 Technique
Risks
While epidurolysis is a safe procedure, potential complications, though rare, can include bleeding, infection, nerve injury, allergic reactions, and catheter shearing. More serious risks like spinal cord ischemia or paralysis are extremely rare but require careful technique to avoid, particularly by ensuring there is always contrast runoff and no loculation (a contained pocket of fluid.
Resources
Article based off of the following video:
References
- ā Gerdesmeyer, Ludger; Noe, Carl; Prehn-Kristensen, Alexander; Harrasser, Norbert; Muderis, Munjed Al; Weuster, Matthias; Klueter, Tim (2021-08). "Long-term Efficacy of Percutaneous Epidural Neurolysis of Adhesions in Chronic Lumbar Radicular Pain: 10 Year Follow-up of a Randomized Controlled Trial". Pain Physician. 24 (5): 359ā367. ISSN 2150-1149. PMID 34323437. Check date values in:
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