A careful history and physical examination that implicates the lumbar facets/zygapophyseal joints and its innervations via the lumbar medial branches of the posterior primary rami as the potential pain generators must be clinically established (Figure 80-1).
Drawings of the nerve supply to the lumbar facet joints (arrows). (A) Anteroposterior view, (B) oblique view.
Physical examination findings that finds direct tenderness on palpation of the skin overlying the lumbar facet joints. Pain is described as deep, dull, achy, diffuse, and in a nondermatomal pattern. Pain may be unilateral of bilateral. Pain is elicited with lumbar spine extension, lumbar spine extension and lateral rotation. Rotational movements, twisting and turning about the axis of the lower lumbar spine causing prevocational pain is suggestive of lumbar facet mediated pain (Figure 80-2).
Pain distribution in the facet syndrome. Referred pain patterns from facet joints reflect the distribution of the segmental nerve supply at each level involved. Distal reference to the buttocks relates to the caudal migration of posterior branches, whereas limb distribution mimicking root pain results from pain reference in the anterior division of each segmental nerve.
Imaging studies including plain radiographs, computed tomography scanning, and magnetic resonance imaging is used to visualize and demonstrate other potential causes of low back pain. CT scan is the gold standard for visualization of the bony architecture of the facet joint, but it does not imply a specific causative pain generator based on degenerative change, inflammation, synovial cyst or other potential derangement.
When a careful history and physical examination implicate the lumbar facet as a potential pain generator and other pain sensitive structures have been excluded.
A controlled series of 2 lumbar medial branch blocks is indicated first with a short-acting local anesthetic (1% lidocaine), and then with a long-acting local anesthetic (0.5% bupivacaine).
There must be a documented benefit from the first short-acting local anesthetic prior to going forward with the long-acting local anesthetic.
Benefit is described as greater than 70% to 80% positive outcome. This can be measured objectively on a visual analogue or numeric pain scale given to the patient post procedure in the form of a “pain diary.”
This can also be measured subjectively in terms of improved functionality with physical therapy and basic activities of daily living, range-of-motion, reduction of medication usage, return to work are a few parameters that may be considered when demonstrating benefit.
If the controlled series of lumbar medial branch blocks are deemed beneficial by the objective and subjective criteria, the next reasonable step in care to provide durable pain relief for the patient is to proceed with radiofrequency neurolysis of the lumbar medial branches of the posterior primary ...