CHAPTER 81: Spinal Injections (Including Epidural Steroids and Medial Branch Blocks)

OVERVIEW

Spinal injections have been performed for many years, most often for the management of axial, paraspinal, and radicular pain. They have evolved over the years with increasing popularity, with the number of epidural steroid injection procedures doubling from 2000 to 2008,¹ and have become essential therapies for the pain management clinician. Spinal injections can be used therapeutically, for treatment, or diagnostically, for the localization and identification of potential painful targets. As a result of their increasing use in pain management and their economic impact, they have been studied extensively, and their efficacies have been challenged. Despite controversy and contradicting results of numerous outcome studies, spinal interventional therapies will likely continue to play a significant role in interdisciplinary pain care.

The purpose of this chapter is to discuss commonly performed spinal interventions, especially epidural steroid injections and facet injections, with an emphasis on information that is clinically relevant to pain management specialists.

HISTORY OF SPINAL INJECTIONS

Spinal injections of substances for the treatment of low back and lower extremity pain^2,3 and for inoperable cancer of the rectum⁴ were described in 1901,⁵ with the use of medications, including cocaine and procaine, via multiple routes of administration, including epidurally, intrathecally, and via the sacral hiatus. In 1909, reports were published on the use of epidural anesthesia for the treatment of sciatica⁶ followed in the 1920s and 1930s by emerging treatments for sciatica with varying degrees of benefit and duration.^7,8

With the discovery of Compound E (cortisone) in 1936^9-11 and by 1950 its improvement of conditions, including rheumatoid arthritis,¹² and with the beneficial intraarticular effects of a longer acting steroid, Compound F (hydrocortisone),¹³ including the histologically confirmed reduction of synovial membrane inflammation, the stage was set for numerous anti-inflammatory pain management procedures along with continuing investigations of its efficacy and mechanisms of actions.^14-20 By the 1950s, many pain management clinics were in operation,^21,22 and today, many interdisciplinary pain treatment facilities are in existence.

CLASSIFICATION OF SPINAL INJECTIONS

Spinal injections for pain management have been performed for many years, both for diagnostic and therapeutic purposes. They can be functionally categorized both by location (i.e., cervical, thoracic, lumbar, or sacral) and by purpose: (i.e., diagnostic or therapeutic). A significant proportion of procedures performed at modern pain clinics include epidural steroid injections and facet joint injections. Other common interventions include sympathetic blocks, provocative discography, and medial branch radiofrequency neurotomy. Epidural steroid injections can be subcategorized by the route of administration of medication, usually via transforaminal, interlaminar, or caudal approaches, with or without the use of a catheter.

Zygapophyseal or facet injections that are therapeutic in nature tend to be intraarticular, and although they can be therapeutic and diagnostic, medial branch blocks are ...