This prospective study was designed to determine the prevalence of lumbar facet joint pain in a consecutive series of patients with chronic low back pain treated at an interventional, multidisciplinary private pain management practice utilizing double diagnostic blocks, to determine the prevalence of false positive rate of uncontrolled facet joint blocks, and to determine the relationship of clinical features of responders and non-responders to double diagnostic blocks.
One hundred and twenty patients with low back pain with or without lower extremity pain were selected. The procedure consisted of diagnostic blocks using lidocaine and bupivacaine on separate occasions, usually two weeks apart. Each facet joint nerve was infiltrated with either 0.4 to 0.6 ml of 1% lidocaine (Xylocaine®) or 1% lidocaine (Xylocaine®) and 0.25% bupivacaine (Marcaine®). A definite response was defined as substantial with at least 75% relief of pain in the symptomatic area following local anesthetic block. Confirmatory blocks using bupivacaine 0.25% were performed at the same levels as the first injection if definite relief was obtained. The response to bupivacaine blocks which lasted longer than the lidocaine blocks was accepted as a positive response. All blocks were performed under fluoroscopic guidance.
Eighty-one patients (67.5%) reported a definite response to lidocaine blocks. Confirmatory blocks with bupivacaine were performed in all 81 patients with 54 patients, i.e. 45% of total sample or 66.6% of lidocaine positive group reporting definite response with a false positive rate of 41%. Prevalence and relationship of pain referral pattern in patients with and without facet joint pain confirmed by double blocks showed no significant correlation. We found no relationship between the history, physical findings, age, gender, trauma, duration of pain, and diagnostic blocks. However, history of previous surgery showed a negative correlation as only 29% of the patients after previous surgery were positive in contrast to 51% of the nonsurgical population.
The results of this study echo previous concerns of reliability of uncontrolled single blocks, history, and clinical features. This study demonstrated that the facet joint is a source of pain in 45% of the patients suffering with chronic low back pain in an interventional pain management setting in a private practice.
Keywords: Low Back Pain, Facet Joints, Double Blocks.