Abstract
Introduction Historically, lumbar discography has been one of the most controversial subjects in the management of discogenic low back pain. The diagnostic value of normal psychometric specific pain provocation by disc pressurization has emerged. The sensitivity, specificity and accuracy of discography as a diagnostic test are not in doubt. In clinical discography pain reproduction and location are essential elements. There is an accepted rate of 0–10% false positives. This rate is influenced by occupational disability and abnormal psychometric profiles. By contrast, little attention has been given to false negative results and their outcomes if surgically treated. Traditionally, whether or not the test is considered to be positive or negative is determined immediately after completion of the diagnostic procedure. This study shows that patient’s pain reproduction may occur up to 24 hours after the discogram which often initially interpreted as a true negative when it is actually a false negative result. This study verifies the existence and significance of a false negative through the patients’ treatment and outcomes.
Methods In this study, 150 patients underwent discography for investigation of chronic persistent low back pain (CPLBP). All patients had a control (morphologically normal) discogram at the level above the degenerative segment. No patients with abnormal psychometric profiles or compensation were included. All patients were followed up 24 hours post discogram by the radiologist to further assess their clinical status. Ten of the patients (7.5%) were considered to have a false negative discogram, as per the Dallas Discogram Scale. The surgeon correlated the delayed response on the subsequent follow-up. These ten patients were diagnosed as having a positive response and were treated surgically for their discogenic pain. VAS-B, VAS-L, ODI, RMD were collected prospectively. Preoperative and 6 month results were reviewed.
Results Seven of the 10 patients (70%) reported severe increase CPLBP and reproduction of pain within 8 hours of the discogram, while 3 patients (30%) did so in the ensuing 24 hours after the discogram. Surgical treatment was either by total disc replacement or anterior lumbar interbody fusion. All patients reported greater than 50% reduction in VAS-B and VAS-L and with improvements of greater than 50% in their ODI and RMD scores.
Discussion The clinical reliability of discography hinges on the subjective assessment of pain concordance as the discriminating factor in determining false positives from false negatives. Given the limitations of discography, all information about the patient should be considered prior to diagnosis, including clinical, radiological, historical, and psychometric factors. The delayed positive discography response is an important consideration for the patient, the radiologist, and the treating surgeon to be aware of. The results of this study verify the existence of this subgroup and justify their surgical treatment.
The abstracts were prepared by Assoc Prof Bruce McPhee. Correspondence should be addressed to him at the Division of Orthopaedics, The University of Queensland, Clinical Sciences Building, Royal Brisbane Hospital, Herston, Brisbane, 4029, Australia.
