李振宙　    侯树勋

Lumbar zygapophyseal joint pain is common and seems to become more prevalent as patients’ age and as the duration of chronic back pain increase. The prevalence is directly and inversely correlated, however, to the stringency of the reference standard. Prevalence studies consistently find the zygapophyseal joint as a common source of pain, but diagnosis using a single anesthetic block has a potential high placebo rate versus a double comparative block control requiring a longer duration of relief after bupivacaine versus lidocaine. Medial branch blocks in the lumbar spine have been repeatedly validated for diagnostic utility. International Spine Intervention Society (ISIS) guidelines suggest that patients should be evaluated for at least 2 hours postinjection, or until relief ceases (whichever occurs first). To be truly diagnostic, relief should also be noted while the patient is attempting activities that are typically aggravating. There exists debate regarding the amount of relief required to consider blocks successful, but 80% pain relief has typically been accepted as the standard for a “positive” response. Radiofrequency neurotomy of the medial branch nerves (and dorsal ramus of L5) has been used extensively to denervate suspected painful facet joints and remains the only available intervention that has demonstrated substantial, long-term relief. With parallel probe placement, significant benefit (60%-80% improvement) may last 6 to 12 months or even longer. Benefit has also been demonstrated with up to 3 repeated treatments, and no limit has yet been established as to how many treatments may result in diminished returns.