The relation between annular disruption on computed tomography scan and pressure-controlled diskography

Objective: To analyze the relation between annular disruption determined by computed tomography (CT) scan and diskographic findings using pressure-controlled manometric diskography. Design: Cross-sectional using prospectively gathered data. Setting: Ambulatory spine intervention unit. Specimens: Two hundred seventy-nine disks from 86 patients (55 men, 31 women) who were referred for diskography of suspected chronic diskogenic low back pain. Interventions: Not applicable. Main Outcome Measures: The grade of annular disruption was rated using CT diskography and fluoroscopic imaging as follows: 0 (no disruption); 1 (extension into the inner third of the annulus); 2 (extension into the middle third of the annulus); 3 (extension into the outer third of the annulus); 4 (circumferential extension with a >30°arc at the disk center); and 5 (contrast media leakage into the outer space). Diskography was performed via a pressure-controlled manometric technique using an injection rate of .05mL/s and a restricted total volume of 3.5mL. Pain was rated on a 0 to10 numeric rating scale (NRS). Criteria for symptomatic disks included provocation of patient concordant pain (NRS score, <6/10) at 50psi or less above opening pressure, with 3.5mL or less of total volume. Symptomatic disks were classified as "low pressure sensitive" or "high pressure sensitive" based on the pressure level that evoked pain. Disks classified as low pressure sensitive required an NRS score of 6 out of 10 or higher at 15psi or less above opening pressure. Disks classified as high pressure sensitive required an NRS score of 6 out of 10 or higher at pressures within a range of 15 to 50psi. Results: The numbers of disks at each annular disruption grade were 19 (6.8%) at grade 0, 29 (10.4%) at grade 1, 35 (12.5%) at grade 2, 42 (15.1%) at grade 3, 69 (24.7%) at grade 4, and 85 (30.5%) at grade 5. A total of 93 disks met the criteria for a symptomatic disk. The extent of annular disruption and the rate of symptomatic disks correlated significantly (P<.001). The highest symptomatic disk rate was observed in grade 4 disks. Of 93 symptomatic disks, 88 (94.6%) showed annular disruption of grade 3 or greater. Disks with grades 0 to 2 and grades 3 to 5 annular disruption differed significantly when the mean NRS relative to intradiskal pressure was compared (P<.001). Comparing the disk type of symptomatic disks at each annular disruption grade, there was a decreasing trend of low pressure sensitive disks relative to the extent of annular disruption (62.5% at grade 3, 39.4% at grade 4, 34.2% at grade 5). Conclusions: Annular disruption reaching the outer annulus fibrosus is a key factor in pain generation. Disk morphology, including annular disruptions extending beyond the outer annulus, may permit increased diskography specificity.