Diagnostic and therapeutic spinal injections

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What specialists perform diagnostic and therapeutic spinal injections?

A diverse community of physicians from many specialties perform spinal injections including anesthesiologists, physiatrists, interventional radiologists, neurologists, and spine surgeons.

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What is the preferred setting for performing spinal injections?

The preferred setting for both diagnostic and therapeutic spinal injections is the sterile environment of an outpatient/ambulatory surgery suite or hospital operating room. Fluoroscopy is used to improve accuracy, safety, and efficacy of injections. Monitoring, including pulse oximetry, blood pressure, and pulse rate, should be performed during the procedure and during the recovery period in case of an adverse reaction to the injected local anesthetic or intravenous sedation. Emergency resuscitating equipment, including crash carts, should be available.

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What are the pain generators of the spine?

Symptoms of axial and radicular pain may be attributed to pathology involving bone, spinal soft tissues (muscles, ligaments, and tendons), intervertebral discs, facet joints, sacroiliac joints, and neurologic structures (spinal cord and nerve roots). The interventional pain physician uses injection techniques in an attempt to identify a specific pain generator responsible for a patient’s symptoms and guide subsequent treatment. It may be challenging or impossible to identify a specific pain generator in the setting of diffuse age-related degenerative spinal pathology. Consensus regarding the scientific basis for a single pain generator to explain the morbidity of chronic axial pain does not exist. The major pain generators of the spine include:

Soft tissue spinal structures: Pain from injury to spinal soft tissue structures including muscles, tendons, and ligaments are the most common disorders responsible for neck and low back pain. This diagnosis is generally based on clinical assessment without the need for interventional procedures. Soft tissue injuries may be classified as strains or sprains, but are more commonly referred to as nonspecific neck or low back pain.

Intervertebral discs: Displaced disc material can impinge on the spinal cord or nerve roots and cause axial and/or radiating pain involving the extremities. Evidence also suggests that the disc itself can cause pain in the absence of neural compression, which is termed discogenic pain . Histologic studies demonstrate the presence of nerve endings throughout the outer third of the annulus fibrosus. These nerve endings are branches of the sinu-vertebral nerves, the gray rami communicantes, and the lumbar ventral rami. Annular tears may result from injury or degeneration. These fissures in the outer margins of the annulus may lead to pain due to mechanical or chemical irritation of these small nerve endings.

Facet joints (zygapophyseal joints or z-joints ) are paired synovial joints in the posterior column of the spine, which are innervated by medial branches of primary dorsal rami. Lumbar facet pathology may result in referred pain involving the buttock, groin, hip, or thigh. Cervical facet joint pathology can manifest as neck pain, referred pain involving the scapular area, or headaches.

Sacroiliac joints are a potential pain generator due to the presence of nociceptors within and adjacent to these joints. However, clinical diagnosis and appropriate treatment remains controversial.

4

List the basic interventional spine procedures.

Epidural injections, medial branch nerve blocks, intraarticular facet joint injections, discography, and sacroiliac joint injections.

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What are the indications for epidural injections?

Treatment of radicular symptoms secondary to disc herniation is the most common and well-supported indication for epidural steroid injections. Epidural steroid injections are also a treatment option for patients with radicular symptoms due to neuroforaminal stenosis or central canal stenosis. Limited evidence supports the role of epidural injections for treatment of axial pain. Epidural injections are also used to aid in localization of symptomatic spinal levels and for treatment of ongoing radicular and/or axial pain following spine surgery.

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What are some contraindications to epidural injections?

Absolute contraindications for epidural steroid injections include: a bleeding disorder or requirement for maintenance on a therapeutic dose of an anticoagulant; systemic or local infection at the injection site; history of significant allergic or hypersensitivity reaction to injected medications or contrast agents; tumor at the injection site; and lack of informed consent. Relative contraindications include uncontrolled diabetes mellitus, congestive heart failure, hypertension, pregnancy, and patients with unrealistic expectations and goals regarding treatment.

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What is the composition of the injectate delivered into the epidural space?

The composition of the injectate varies and may include a corticosteroid, local anesthetic, or normal saline, either singly or in combination. Corticosteroids are used in epidural injections because of their inhibitory effects on cytokines and chemokines generated at sites of inflammation, as well as their suppressive effects on leukocyte distribution, aggregation, and function, but are not approved by the US Food and Drug Administration (FDA) for this indication. Corticosteroids used for epidural injections differ with respect to microscopic particle size, solubility, and duration of effect, and are classified as particulate (methylprednisolone, triamcinolone and betamethasone) or nonparticulate (dexamethasone). As particulate steroids are insoluble in water, these medications may bind and form sizeable aggregates, increasing the risk of blood vessel occlusion. The potential for particulate steroids to embolize following inadvertent intravascular injection and occlude terminal blood vessels in the brain or spinal cord has been linked to catastrophic neurologic injuries, particularly following transforaminal epidural injections.

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