Pressure Increase in Adjacent Discs During Clinical Discography Questions the Methods Validity

Abstract

STUDY DESIGN: Observational in vivo clinical study. OBJECTIVE: To investigate whether intradiscal pressure is transferred to adjacent discs during clinical discography in subjects with discogenic pain. SUMMARY OF BACKGROUND DATA: Despite the introduction of pressure registration in discography, the validity of the method remains controversial. Discography in vivo in anesthetized pigs has shown that the pressure increase during disc injection is transmitted to adjacent discs. If pressure transmission is confirmed in human spines, it could be a potential source of false-positive discography responses. METHODS: Twenty-five discograms were performed in 9 consecutive patients. A pressure sensor was introduced through a 22-gauge needle into the nucleus pulposus in 2 adjacent discs. Contrast was injected with a manometer (∼0.05 mL/s) into one of the discs, whereas intradiscal pressure was measured simultaneously in both discs. The injection continued until one of the endpoints was reached; concordant pain with an intensity of 5/10 or more, intradiscal pressure of 80 psi (absolute pressure), and/or 3.5-mL contrast volume. RESULTS: Intradiscal pressure was successfully measured in 22 adjacent discs of which 7 were not filled with contrast and 15 were prefilled from the previous discogram. A mean pressure increase of 13 psi (range, 3-42 psi) was recorded in 55% (12) of the adjacent discs, corresponding to an increase of 62% above baseline. Of discograms inducing pressure transmission, all had Pfirrmann degeneration grade of 3 or more and, of adjacent discs with increased pressure, 75% had degeneration of 3 or more. Maximum pressure in injected discs averaged 35 psi above opening pressure (range, 10-69 psi). CONCLUSION: Clinical discography induces a pressure increase in adjacent discs. The induced pressure increase was of a clinically relevant magnitude and was evident despite low absolute pressures in the injected disc. Pressure transmission during discography constitutes a potential major source of false-positive responses, questioning the ability of discography to provoke pain at just a single disc level. LEVEL OF EVIDENCE: 1.