The Peridural Membrane of the Spinal Canal: A Critical Review

Percutaneous Foraminal Neuroplasty Using Reference Spinal Needles: Technical Description

BACKGROUND

Lumbar foraminal stenosis is a common cause of chronic lower back pain and radiculopathy often treated by epidural steroid injections. In the absence of imaging findings with a positive physical exam demonstrating symptoms, percutaneous neuroplasty (PNP) may be an alternative to transforaminal epidural steroid injections that have otherwise failed.

CASE PRESENTATION

We present two cases (55-year-old man and 65-year-old woman) with chronic low back pain and radiculopathy with otherwise normal imaging demonstrating no lumbar foraminal stenosis refractory to transforaminal epidural steroid injections. PNP was performed using reference spinal needles with both patients achieving sustained > 50-75% pain relief.

CONCLUSION

PNP offers interventional chronic pain physicians and patients with refractory chronic low back pain with lumbar radiculopathy due to fibrosis an alternative, safe treatment that offers sustained results. Furthermore, this is the first of its kind to offer a step-by-step procedural step of PNP using a reference spinal needle.

The peridural membrane of the spine has characteristics of synovium

The peridural membrane (PDM) is a well-defined structure between dura mater and the wall of the spinal canal. The spine may be viewed as a multi-segmented joint, with the epidural cavity and neural foramina as joint spaces and PDM as synovial lining. The objective of this investigation was to determine if PDM has histological characteristics of synovium. Samples of the PDM of the thoraco-lumbar spine were taken from 23 human cadavers and analyzed with conventional light microscopy and confocal microscopy. Results were compared to reports on similar analyses of synovium in the literature. Histological distribution of areolar, fibrous, and adipose connective tissue in PDM was similar to synovium. The PDM has an intima and sub-intima. No basement membrane was identified. CD68, a marker for macrophage-like-synoviocytes, and CD55, a marker for fibroblast-like synoviocytes, were seen in the lining and sub-lining of the PDM. Multifunctional hyaluronan receptor CD44 and hyaluronic acid synthetase 2 marker HAS2 were abundantly present throughout the membrane. Marked presence of CD44, CD55, and HAS2 in the well-developed tunica muscularis of blood vessels and in the body of the PDM suggests a role in the maintenance and lubrication of the epidural cavity and neural foramina. Presence of CD68, CD55, and CD44 suggests a scavenging function and a role in the inflammatory response to noxious stimuli. Thus, the human PDM has histological and immunohistochemical characteristics of synovium. This suggests that the PDM may be important for the homeostasis of the flexible spine and the neural structures it contains.

The anatomy of the peridural membrane of the human spine

A peridural membranous layer exists between the bony wall of the spinal canal and the dura mater, but reports on the anatomy of this structure have been inconsistent. The objective of this study is to give a precise description of the peridural membrane (PDM) and to define it unambiguously as a distinct and unique anatomical entity. Thirty-four cadaveric sections of human thoraco-lumbar spines were dissected. On gross examination, the PDM appears as a smooth hollow tube that covers the bony wall of the spinal canal. An evagination of this tube into the neural foramen contains the exiting spinal nerve. The entire epidural venous plexus, including its extension into the neural foramina, is contained in the body of the PDM. Histological examination of the PDM shows a variable distribution of veins arteries, lymphatics, and nerves embedded in a continuous sheath of fibrous, areolar, and adipose tissue. The posterior longitudinal ligament may be considered a dense condensation of fibrous tissue within the membrane. Thus, the PDM is a unique, continuous, and complete anatomical structure. In the spinal canal, the PDM is adjacent to the periosteum. In the neural foramen, suprapedicular PDM and pedicular periosteum separate anatomically to form a suprapedicular compartment, bounded anteriorly by the intervertebral disc and posteriorly by the facet joint. Trauma or degeneration of the disc or facet joint may lead to inflammation and pain sensitization of PDM. This protective mechanism may be of considerable importance for the functioning of the spine under conditions of strain.

Ventral epidural filling technique in interlaminar epidural steroid injection

STUDY DESIGN

A retrospective case-control study.

OBJECTIVE

To evaluate the safety and efficacy of the ventral epidural filling technique in lumbar interlaminar epidural steroid injection (ESI).

SUMMARY OF BACKGROUND DATA

The ventral epidural space can be a preferred target in ESI because it contains many spinal pain generators. However, there have been few studies regarding the ventral epidural space filling technique in interlaminar ESI.

METHODS

This study involved a retrospective analysis of 150 consecutive patients treated with the ventral epidural filling technique in interlaminar ESI (ventral ESI) and a control cohort of 150 consecutive patients treated with the dorsal epidural filling technique in interlaminar ESI (conventional ESI). The visual analogue scale for leg pain, the visual analogue scale for back pain, and the Oswestry Disability Index were compared at preinjection and 2 weeks, 6 weeks, 6 months, and 1 year postinjection. The groups were compared with regard to repeated injection or surgery within 1 year after the initial procedure. The fluoroscopic time and the procedure-related complications including severe pain (visual analogue scale score>7) during injection, dural puncture (subdural contrast spread), headache, neurological symptoms, and infection were also compared.

RESULTS

There were no significant differences in leg pain, back pain, or Oswestry Disability Index improvement at each visit between the ventral ESI group and the conventional ESI group (all P>0.05). The numbers of repeat injections and surgical procedures were not significantly different between 2 groups (P=0.262 and 0.385, respectively). There were no significant differences in severe pain at injection (P=0.326), dural puncture (P=0.428), headache (P=0.393), neurological symptom (P=0.419), or infection (P=0.500) between the 2 groups. The fluoroscopic time was significantly shorter in ventral than in conventional ESI (P<0.000).

CONCLUSION

The ventral epidural filling technique can be performed safely and more easily during lumbar interlaminar ESI. The clinical results and procedure-related complications with this technique were comparable with those seen with conventional interlaminar ESI.

LEVEL OF EVIDENCE

3.

Low-back pain

Low-back pain is one of the most common painful conditions experienced by humans throughout their life. Some occupational risk factors (namely, heavy manual material handling) may also contribute to the development of low-back pain: due to the high prevalence of both low-back pain and manual material handling in the adult working population, it has been estimated that low-back pain is probably the most common occupational disorder worldwide. Lifetime prevalence of low-back pain has been reported to be as high as 84%, depending on the case definition used, and no age group is spared, even children. Although low-back pain is not a lethal condition, it was estimated at the third rank among all diseases by disability-adjusted life-years in 2010 in the USA, after ischemic heart disease and chronic obstructive pulmonary disease, and at the first rank by years lived with disability. It also ranked high (13th) globally for the same year, in disability-adjusted life-years. Low-back pain is currently classified as nonspecific/specific as to putative cause and as acute (lasting less than 6 weeks), subacute (6-12 weeks), or chronic (more than 12 weeks) according to duration of symptoms. The distinction between nonspecific/specific and acute/subacute/chronic low-back pain is useful not only for epidemiologic studies, but also (mainly) for choosing the appropriate strategy for the diagnosis and treatment of the disorder. Workplace risk factors for low-back pain include manual lifting and whole-body vibration exposure. This chapter will provide an overview of modern concepts of low-back pain (in general) and will then outline some distinctive features of work-related low-back pain.

Epiduroscopy for patients with lumbosacral radicular pain

Lumbosacral radicular pain is a pain in the distribution area of one of the nerves of the lumbosacral plexus, with or without sensory and/or motor impairment. A major source of lumbosacral radicular pain is failed back surgery, which is defined as persistent or recurrent pain, mainly in the region of the lower back and legs even after technically, anatomically successful spine surgeries. If lumbosacral radicular neuropathic pain fails to respond to conservative or interventional treatments, epiduroscopy can be performed as part of a multidisciplinary approach. Epiduroscopy aids in identifying painful structures in the epidural space, establishing a diagnosis and administering therapy. The novelty consists in the use of an epiduroscope to deliver therapies such as adhesiolysis and targeted administration of epidural medications. Clinical trials report favorable treatment outcomes in 30% to 50% of patients. Complications are rare and related to the rate or volume of epidural fluid infusion or inadvertent dural puncture. In patients with lumbosacral radicular pain, especially after back surgery, epiduroscopy with adhesiolysis may be considered (evidence rating 2 B+).

A review of the role of epidural percutaneous adhesiolysis

SUMMARY Low back and leg pain can arise for a variety reasons, including epidural scarring caused by post lumbar surgery syndrome, infection or bleeding. Treatment options for low back and/or leg pain caused by epidural scarring include conservative approaches, such as physical therapy and medication management, and procedures, such as epidural steroid injections. Despite appropriate treatment, pain can persist in these patients. Surgery is often not an option for patients whose pain is caused by scarring. Percutaneous adhesiolysis is a minimally invasive technique, which is effective in treating refractory low back and leg pain arising from epidural scarring. It involves the use of a spring-wound, shear-resistant catheter, ideally placed in the ventrolateral aspect of the epidural space for the lysis of adhesions, allowing medications to reach the involved nerve and removing compression of the nerve. After mechanical lysis of adhesions, relatively large volumes of local anesthetic, saline, steroid and radiopaque contrast material are injected. Either hypertonic or normal saline may be used, along with hyaluronidase. After the procedure, the patient should perform exercises to stretch the nerve roots. While this has been studied as a caudal procedure, thoracic and cervical procedures have also been described, using both transforaminal and interlaminar approaches. With trained practitioners, complications are minimal. The effectiveness of the procedure has been documented by high-quality randomized controlled trials and observational studies for both postlumbar surgery syndrome and spinal stenosis.