Facet joint block for low back pain: identifying predictors of a good response.

This preliminary study was conducted to identify a facet joint syndrome in low back pain. Ninety maneuvers and symptoms were compared between patients relieved (responders) and those unrelieved (nonresponders) after intraarticular blocks. Fifty-one patients participated in the study; 11 were excluded from evaluation because of unsuccessful injection into the joints as planned. Of the 40 patients included, 20 had four joints anesthetized, 16 had two joints anesthetized, and four had three joints anesthetized. Twenty-two were responders, 17 of whom had more than 90% relief of pain. Only a few variables were more frequent in the responder group: older age, absence of exacerbation by coughing, relief when recumbent, absence of exacerbation by forward flexion and when raising from this flexion, absence of worsening by hyperextension, and extension-rotation. When four of these seven variables were present in the same patient, sensitivity was 81.8% and specificity 77.8%, but this discriminant power must be evaluated in a new population.