In patients with chronic radicular pain, with or without axial pain, transforaminal epidural steroid injection (TFESI) has been a common treatment. However, the beneficial effect may only last a short time or may not be as effective potentially as a result of epidural/foraminal adhesions that prevent the medication from reaching the affected area in an optimal way. In these cases, an alternative treatment option may be PNP.

One of the key targets when performing PNP is the peridural membrane (PM), a thin, well-innervated structure between dura mater and the wall of the spinal canal. Fibrosis of the PM can be a possible cause of low back pain when other causes of facetogenic or discogenic pain have been ruled out [7, 8]. The level of evidence (LOE) for PNP varies for conditions being treated such as spinal stenosis (LOE II), lumbar disc herniation (2), and post-laminectomy syndrome (I) [9,10,11]. PNP also offers an alternative treatment modality when traditional methods such as transforaminal epidural steroid injections have failed because of fibrosis [12].

In PNP, the epidurogram plays a vital role given its correlation with the patient’s clinical condition and offers additional information unavailable from MRI such as when there is chronic lower back pain with or without radicular pain in the absence of central canal or foraminal stenosis on MRI [13, 14]. Whereas, the epidurogram allows for visualization via a filling defect in the presence of fibrosis, which may be causing the compression.

Four different approaches, all equal in effectiveness, have been described for PNP, with the classic and first approach via the sacral hiatus and others being via the S1 foramen, interlaminar, and transforaminal [15, 16]. The choice of approach depends on the feasibility of the target or if one approach does not allow access when tried. Of note, stenosis of both the foramen and central canal can be present and prevent movement of the catheter from the midline to the foramen because of the central canal stenosis. In these instances, foraminal access as the initial step may be indicated.

The reference needles help guide our final epidural needle towards the target, adding a third dimension (depth) to a fluoroscopy-guided procedure, which is inherently two-dimensional. This depth dimension provided by the reference spinal needle allows us to tailor our approaches according to the patient’s needs, directing them towards the affected area or the region most likely accessible with the neuroplasty catheter. Ultimately, access to the foramen is achieved with the catheter, not the epidural needle, making the approach safer.

It is important to note that the utilization of reference needles for controlling depth in fluoroscopy-guided procedures extends beyond foraminal neuroplasty cases. It could also be applicable in procedures utilizing non-coaxial or non-tunnel vision approaches. This broadens the scope for exploring various procedures and expands the potential applications of this technique.

This technique was meticulously developed to provide a systematic approach for conducting foraminal neuroplasty based on the affected or narrowed area, and its preliminary findings show promise. However, further research is needed to establish the effectiveness of this technique relative to existing methodologies and technology.

Furthermore, a critical aspect of this manuscript pertains to the absence of a control group utilizing an alternative technique, coupled with the relatively limited number of enrolled patients. Considering that participants are aware of receiving a more targeted therapy, the potential influence of a placebo effect must be acknowledged.