Correlation Between MR Imaging And CT Discography With Provocative Concordant Pain In Patients With Discogenic Low Back Pain

Background:Low back pain (LBP) is one of most common symptoms encountered by primary care physicians. One of its prominent sources is the discogenic pain, a term synonymous with internal disc disruption (IDD). Crock defined IDD as an "alteration in the internal architecture of the disc, specifically excluding the escape of the disc fragment from the confines of the space (annulus)."Discography as a pain provocation test is considered as the only method to relate a radiographic image to the patient’s pain directly.From an empirical standpoint, discography is the best tool to evaluate discogenic LBP. However, because of its invasiveness, radiation exposure, and infectious risk, discography has been controversial since its beginning. Magnetic resonance imaging (MRI) is a highly accurate method in detecting morphologic abnormalities of the degenerative discs. Although MRI was found to be sensitive for the identification of degenerative discs, it was unreliable at identifying the symptomatic disc levels. Some early studies have attempted to correlate the MRI features of disc degeneration with pain reproduction at discography; however, the results were controversial. Therefore, in this study we tried to find out if discogenic lumbar pain was associated with discographic findings and magnetic resonance (MR) findings including disc degeneration (Pearce grade), high-intensity zone (HIZ), and endplate abnormality (Modic change) based on the pain response during discography.Objective:To explore correlation of MR findings and CT discography (CTD) with provocative concordant pain in patients with discogenic low back pain (DLBP).Methods:From December2009to December2012,76patients (52men and24women, mean age39.3±3.8y, age range18to67y) were enrolled in the study. All patients underwent MR imaging of the lumbar spine and subsequent provocation discography as part of a clinical evaluation of low back pain in the study. MR images were then evaluated for disc degeneration, HIZ, and endplate Modic change. In the procedure of discography, concordant pain was denoted as positive, whereas discordant pain and no pain were denoted as negative. Based on MR findings, CT discography was successfully carried out on209discs in76patients with DLBP, We evaluated correlation among the CTD group、dose of contrast medium、concordant pain by discography and MR findings.Finally,MR and discographic findings were analyzed byχ2test based on results of concordant pain. Dose of contrast medium and results of concordant pain were analyzed by t test.Results:Discography was conducted on209discs successfully,83discs of which presented with concordant pain, and the others presented with discordant pain. There were36 discs were evaluated as CTDIII on discographic finding,7of which presented with concordant pain;58were evaluated as The CTD II,46of which presented with concordant pain;26were evaluated as The CTDⅣ,23of which presented with concordant pain. CTD groups was significant correlated with discographic findings, CTDIII and CTD II have significant difference (χ2=19.98, P<0.01, r=0.57), CTDIV(x2=25.38, P<0.01, r=0.62). The numbers of contrast medium from positive and negative discs have significant difference (t=6.61, P<0.01).MR findings of discs and provocative concordant pain by CTD have significant correlation. There were125discs were evaluated as Grade Ⅰ-Ⅲ on MR images,16of which presented with concordant pain;84were evaluated as Grade Ⅳ-Ⅴ,67of which presented with concordant pain. The endplate abnormalities were observed in39discs,32of which manifested concordant pain. HIZ was found in48discs,41of which had concordant pain. Concordant pain was significant correlated with Grade IV-V disc degeneration on MR image (χ2=94.09, P<0.01, r=0.67), the presence of HIZ (χ2=39.93, P<0.01, r=0.43), and endplate abnormalities (χ2=28.93, P<0.01, r=0.37).Discussion:CTD can show the sign of internal disc disruption directly, identified the symptomatic disc. CTD Ⅱ and CTDⅣ discs on discography, Grade IV-V disc on MR images, the presence of HIZ, and endplate abnormalities might indicate discogenic pain in patients with chronic low back pain.