Below is from 2004 CPT Assistant that expands on indications for facet injections and potentially facet joint nerve denervation
Indications for Treatment
"Repetitive stress and osteoarthritic changes to the facet joint can lead to facet hypertrophy. Facet joint injections can provide relief of pain caused by an arthritic spine joint. Like any synovial joint, degeneration, inflammation, and injury can lead to pain upon joint motion. In addition, facet arthrosis, particularly trophic changes of the superior facet, can progress to narrowing of the neural foramen (the doorway through which the spinal nerves leave the spinal canal to spread out into the body). This neural foramen can be narrowed by disc herniations, spurs from the margin of the vertebral body, or spurs from the facet joints. Facet hypertrophy can contribute to lateral and central lumbar stenosis, which can lead to impingement on the exiting nerve root. Symptomatic injury to the facet joints (zygapophysial joints) has also been documented in the cervical and lumbar spine following blunt trauma, even in the absence of degenerative changes. No consistent radiographic findings (or the absence of radiographic findings) has been correlated clinically with the presence or absence of pain of facet joint origin. The controlled medical literature supports the primary use of facet (or facet nerve) injection as a sensitive diagnostic procedure to determine the presence or absence of facet pain.
The spinal cord is a two-way communication path to the brain stem that relays nerve impulses between the spinal cord and other parts of the brain and the peripheral nervous system. During this complex process, even the brain can encounter difficulty localizing the internal structures of the spine. This is evident when facet joint pain produces a pain referral pattern indistinguishable from disc herniation or other structural sources of pain. Diagnostic and therapeutic facet joint injections or facet joint nerve injections are performed to obtain more precise information regarding pain generation, sort out complex spinal pain patients, and plan operative interventions."