Discography Summary: Section 2

Regardless of the exact classification scheme used, it is important to note the degree of annular degeneration, the presence of annular fissures, and whether the annulus is competent or incompetent.

If a patient has a convincing pain response but no evidence of a radial annular fissure on discography post-discography CT scanning should be considered, as some discs which are normal on discography are disrupted on CT-discography.

Sachs, et al. Dallas Discogram Description. A New Classification of CT/Discography in Low Back Disorders. Spine 1987;12:3;287-94.

In that circumstance an annulogram can also be considered, in the event there is primary annular pathology.

In addition to annular pathology both Schmorls nodes and endplate disruptions should be noted, as they may be clinically significant.

Malmivaara, et al. Plain Radiographic, Discographic, and Direct Observations of Schmorls nodes in the Thoracolumbar Junctional Region of the Cadaveric Spine. Spine 1987;12:5;453-7.

Hsu, et al. Painful Lumbar endplate Disruptions: A Significant Discographic Finding. Spine 1988;13:1;76-79.

If a patient has at least one disc that is both normal structurally and does not elicit a pain response that is considered by some to serve as a control disc. A control injection may be helpful in deciding whether a pain response at another disc is a true positive result or reflects an exaggerated reaction to nociception. However, a more valid control would probably be a structurally abnormal disc. While the significance of the results from control injections have not been formally validated, clinical experience suggests that if at least one structurally abnormal disc does not hurt then pain provoked at another disc is more likely to be a true positive.

As a final note, there are some who do not believe that discography is necessary prior to fusion, as they feel that the diagnosis of discogenic pain can be made by clinical and radiographic criteria.

There is substantial data suggesting that the clinical exam is of minimal use in discriminating between potential axial pain generators (1,2). A possible exception to this is a McKenzie mechanical assessment, which may be able to predict the results from discography (3).

(1) Schwarzer, et al. The Relative Contributions of the Disc and Zygapophyseal Joint in Chronic Low Back Pain. Spine 1994;19:7;801-6.

(2) Schwarzer, et al. The Sacroiliac Joint in Chronic Low Back Pain. Spine 20;1995 20:1;31-7.

(3) Donelson and April paper published last year.

There have been several studies demonstrating that MRI cannot reliably predict which discs are painful on discography, at least to the level of confidence required to rely solely on MRI for surgical decision making.

Osti, et al. MRI and discography of annular tears and intervertebral disc degeneration. A prospective clinical comparison. JBJS (Br) 1992;74B:431-5. correlating MRI findings with the results from provocative discography.

Simmons, et al. Awake Discography. A Comparison Study with Magnetic Resonance Imaging. Spine 1991;16:6;S216-21.

Zucherman, et al. Normal Magnetic resonance Imaging with Abnormal Discography. Spine 1988;13:12;1355-9.

A high intensity zone in the posterior annulus, as visualized on MRI, has recently been proposed as a marker for painful discs.

April, C. High-intensity zone: a diagnostic sign of painful lumbar discs on magnetic resonance imaging. British Journal of Radiology 1992;65:361-9.

Schellhas, K. Lumbar disc high-intensity zone. Correlation of magnetic resonance imaging and discography. Spine 1996;21:79-86.

While highly specific, the sensitivity of this finding is only 26%, which limits the usefulness of the HIZ in selecting patients for surgery.

Saifuddin, et al. The value of lumbar spine magnetic resonance imaging in the demonstration of annular tears. Spine 1998;23(4):453-7.

If a patient undergoes a fusion for lumbar axial pain without preoperative discography both the patient and the surgeon should be aware that the level adjacent to the planned fusion may be a source of clinical symptoms, regardless of the findings on MRI scan.