CAPACITY OF THE CLINICAL PICTURE TO CHARACTERIZE LOW-BACK-PAIN RELIEVED BY FACET JOINT ANESTHESIA - PROPOSED CRITERIA TO IDENTIFY PATIENTS WITH PAINFUL FACET JOINTS

Study Design. Prospective randomized study to compare the efficacy of facet joint injection with lidocaine and facet joint injection with sa line in two groups of patients with low back pain, with and without cl inical criteria that were determined in a previous study to implicate the facet joint as the primary source of the pain. Objectives. To asse ss the efficacy of single facet joint anesthesia versus placebo (salin e injections) and to determine clinical criteria that are predictive o f significant relief of LBP after injection. Summary of Background Dat a. There is no syndrome that discriminates between lower back pain cau sed by facet joint and that caused by other structures. Single or doub le facet joint anesthesia, and single photon emission computed tomogra phy are expensive and time-consuming procedures for selecting patients in controlled clinical trials with large populations. Methods. Result s of a previous study showed that seven clinical characteristics were more frequent in patients who responded to facet joint anesthesia than in those who did not. In the current study, a group of 43 patients wi th lower back pain who met at least five criteria were compared with 3 7 patients who met fewer criteria. Patients randomly received injectio n of either lidocaine or saline into the lower facet joints. The resul t was considered positive if more than 75% pain relief was determined by visual analog scale. The patient, the radiologist, and the investig ator were blinded. An analysis of variance was used to seek an interac tion between clinical group effect and injection effect, and logistic regression analysis to select the best set of variables that would be predictive of minimum pain relief of 75% after; the injection. Results . There was a significant interaction between clinical group and injec tion effect (P = 0.003). In patients with back pain, lodocaine provide d greater lower back pain relief than saline: (P = 0.01). Lidocaine al so provided greater pain relief in the back pain group than in the the nonpain group (P = 0.02). This presence of five among seven variables (age greater than 65 years and pain that was not exacerbated by cough ing, not worsened by hyperextension, not worsened by forward flexion, not worsened when rising from flexion, not worsened by extension-rotat ion, and well-relieved by recumbency); always including the last item, distinguished 92% of patients responding to lidocaine injection and 8 0%. of those not responding in the lidocaine group. Conclusions. A set of five clinical characteristics can be used in randomized studies to select lower back pain that will be well relieved by facet joint anes thesia. These characteristics should not, however, be considered as de finite diagnostic criteria of lower back pain originating from facet j oints.