BACKGROUND: Only controlled intra-articular zygapophyseal joint (ZJ) injections or medial branch blocks can diagnose ZJ-mediated low back pain. The low prevalence of ZJ pain implies that identification of clinical predictors of a positive response to a screening block is needed.
PURPOSE: To estimate the predictive power of clinical findings in relation to pain reduction after screening ZJ blocks.
STUDY DESIGN: As part of a wider prospective blinded study investigating diagnostic accuracy of clinical variables, a secondary analysis was carried out to seek evidence of variables potentially valuable as predictors of screening ZJ block outcomes.
PATIENT SAMPLE: Chronic low back pain patients received screening ZJ blocks (n=151) with 120 patients included in the analysis after exclusions.
OUTCOME MEASURES: Pain intensity was measured using a 100-mm visual analog scale, and responses were categorized according to 75% through 95% or more pain reduction in 5% increments.
METHODS: Patients completed pain drawings, questionnaires, and a clinical examination before screening lumbar ZJ blocks. History, demographic and clinical variables were evaluated in cross tabulation and regression analyses with diagnostic accuracy values calculated for variables and variable clusters in relation to different pain reduction standards.
RESULTS: At the 75% pain reduction standard, 24.5% responded to screening ZJ blocks and 10.8% responded at the 95% standard. The centralization phenomenon is not associated with pain reduction using any standard. No variables were useful predictors of post-ZJ block pain reduction of less than 90%. Seven clinical findings were associated with 95% pain reduction after blocks. Five useful clinical prediction rules (CPRs) were found for ruling out a 95% pain reduction (100% sensitivity), and one CPR had a likelihood ratio of 9.7, producing a fivefold improvement in posttest probability.
CONCLUSIONS: A negative extension rotation test, the centralization phenomenon, and four CPRs effectively rule out pain ablation after screening ZJ block. One CPR generates a fivefold improvement in posttest probability of a negative or positive response to ZJ block.
Facet joints, as a source of low back pain, have attracted considerable attention and been a source of controversy in recent years. Significant progress has been made in precision diagnosis of chronic low back pain with neural blockade. In the face of less than optimal diagnostic information offered by imaging and neurophysiologic studies, and in the face of mounting evidence showing lack of correlation between clinical features, physical findings, and diagnosis of facet joint mediated pain, controversial features have been described to validate the assumption of facet joint mediated pain by set criteria. The prevalence of lumbar facet joint mediated pain in patients with chronic low back pain has been established in this study as 42% using controlled comparative local anesthetic diagnostic blocks, with a false positive rate of 37%. The evaluation of role of various clinical features described in the literature, six features showed negative correlation with facet joint mediated pain. However, these six feature involved only a small number of patients. In conclusion, facet joint mediated pain is a common entity in patients suffering with chronic low back pain nonresponsive to conservative care, who present to a nonuniversity pain management practice. However, the history, clinical features, and radiological features are of no significance or assistance in making the diagnosis of facet joint mediated pain with certainty.
<b>STUDY DESIGN: </b>Prospective randomized study to compare the efficacy of facet joint injection with lidocaine and facet joint injection with saline in two groups of patients with low back pain, with and without clinical criteria that were determined in a previous study to implicate the facet joint as the primary source of the pain.<b>OBJECTIVES: </b>To assess the efficacy of single facet joint anesthesia versus placebo (saline injections) and to determine clinical criteria that are predictive of significant relief of LBP after injection.<b>Summary Of Background Data: </b>There is no syndrome that discriminates between lower back pain caused by facet joint and that caused by other structures. Single or double facet joint anesthesia, and single photon emission computed tomography are expensive and time-consuming procedures for selecting patients in controlled clinical trials with large populations.<b>METHODS: </b>Results 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 with lower back pain who met at least five criteria were compared with 37 patients who met fewer criteria. Patients randomly received injection of either lidocaine or saline into the lower facet joints. The result was considered positive if more than 75% pain relief was determined by visual analog scale. The patient, the radiologist, and the investigator were blinded. An analysis of variance was used to seek an interaction 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.<b>RESULTS: </b>There was a significant interaction between clinical group and injection effect (P = 0.003). In patients with back pain, lidocaine provided greater lower-back pain relief than saline (P = 0.01). Lidocaine also-provided greater pain relief in the back pain group than in the nonpain group (P = 0.02). The presence of five among seven variables (age greater than 65 years and pain that was not exacerbated by coughing, not worsened by hyperextension, not worsened by forward flexion, not worsened when rising from flexion, not worsened by extension-rotation, and well-relieved by recumbency), always including the last item, distinguished 92% of patients responding to lidocaine injection and 80% of those not responding in the lidocaine group.<b>CONCLUSIONS: </b>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 anesthesia. These characteristics should not, however, be considered as definite diagnostic criteria of lower back pain originating from facet joints.
One hundred seventy-six consecutive patients with chronic low-back pain and no history of previous lumbar surgery were studied to test the clinical criteria of Fairbank et al. and Helbig and Lee for zygapophysial joint pain. All patients underwent a history, examination, and a series of zygapophysial joint injections or blocks of the medial branches of the dorsal ramus with lignocaine. Those patients responding to the first series of blocks were given confirmatory blocks using bupivacaine. None of the clinical features tested was found to be associated with response to the confirmatory block. The Fairbank et al. and Helbig and Lee criteria were shown to be unreliable in distinguishing pain of zygapophysial joint origin from pain of other origins.
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.
Only controlled intra-articular zygapophyseal joint (ZJ) injections or medial branch blocks can diagnose ZJ-mediated low back pain. The low prevalence of ZJ pain implies that identification of clinical predictors of a positive response to a screening block is needed.
PURPOSE:
To estimate the predictive power of clinical findings in relation to pain reduction after screening ZJ blocks.
STUDY DESIGN:
As part of a wider prospective blinded study investigating diagnostic accuracy of clinical variables, a secondary analysis was carried out to seek evidence of variables potentially valuable as predictors of screening ZJ block outcomes.
PATIENT SAMPLE:
Chronic low back pain patients received screening ZJ blocks (n=151) with 120 patients included in the analysis after exclusions.
OUTCOME MEASURES:
Pain intensity was measured using a 100-mm visual analog scale, and responses were categorized according to 75% through 95% or more pain reduction in 5% increments.
METHODS:
Patients completed pain drawings, questionnaires, and a clinical examination before screening lumbar ZJ blocks. History, demographic and clinical variables were evaluated in cross tabulation and regression analyses with diagnostic accuracy values calculated for variables and variable clusters in relation to different pain reduction standards.
RESULTS:
At the 75% pain reduction standard, 24.5% responded to screening ZJ blocks and 10.8% responded at the 95% standard. The centralization phenomenon is not associated with pain reduction using any standard. No variables were useful predictors of post-ZJ block pain reduction of less than 90%. Seven clinical findings were associated with 95% pain reduction after blocks. Five useful clinical prediction rules (CPRs) were found for ruling out a 95% pain reduction (100% sensitivity), and one CPR had a likelihood ratio of 9.7, producing a fivefold improvement in posttest probability.
CONCLUSIONS:
A negative extension rotation test, the centralization phenomenon, and four CPRs effectively rule out pain ablation after screening ZJ block. One CPR generates a fivefold improvement in posttest probability of a negative or positive response to ZJ block.
