Atlas of Image-Guided Intervention in Regional Anesthesia and Pain Medicine Chapter 7 Facet injection
Highlights
- The sensory innervation to the facet joints is anatomi-
cally predictable, and the sensory nerves are easily acces-
sible from the dorsal surface of the body (View Highlight)
- The anterior
ramus contains the majority of sensory and motor fi bers
at each vertebral level (View Highlight)
- The posterior primary ramus, in
turn, divides into a lateral branch that provides innerva-
tion to the paraspinous musculature and a small, variable
sensory branch to the skin overlying the spinous processes (View Highlight)
- the medial branch of the posterior primary ramus courses
over the base of the transverse process where it joins with
the superior articular process of the facet joint and courses
along the articular process to supply sensation to the joint. (View Highlight)
- Each facet joint receives sensory innervation from the
medial branch nerve at the same vertebral level, as well as
from a descending branch from the vertebral level above;
thus, two medial branch nerves must be blocked to anes-
thetize each facet joint, for example, medial branch blocks
at the base of the L4 and L5 transverse processes are needed
to anesthetize the L4/L5 facet joint (View Highlight)
- The pain caused by facet arthropathy is most
pronounced over the axis of the spine itself and is typically
maximal directly in the region of the most affected joints (View Highlight)
- Conventional radiofrequency treatment produces a
small area of tissue coagulation surrounding the active tip
of an insulated cannula (View Highlight)
- By applying the radiofre-
quency energy in intermittent pulses, the voltage energy
can be delivered without heating of the tissue or resultant
tissue coagulation. (View Highlight)
- The
lesion produced by conventional radiofrequency is along
the shaft of the needle surrounding the active tip (see
Fig. 7-20). There is scant tissue destruction at the tip of the
needle; thus, the shaft of the active tip of the cannula must
be placed along the course of the nerve (View Highlight)
- the
highest density of voltage change during pulsed radiofre-
quency emanates directly from the tip of the radiofrequency
cannula; thus, the tip of the needle should be directed along
the course of the nerve to be treated (View Highlight)
- The medial branch nerves to the lumbar facets course over
the base of the transverse process, where they join with
the superior articular processes (View Highlight)