The transfer of disc pressure to adjacent discs in discography: a specificity problem?

In vivo experimental study.

The primary objective of the study was to investigate pressure transmission to adjacent discs during discography. A secondary objective was to quantify the transmitted pressure, both in contrast injected and noninjected porcine intervertebral discs.

Discography is used to before surgery identify painful discs. A pain response during discography that is concordant with the patient's experienced back pain is regarded as an indication that the injected disc is the source of pain. However, the sensitivity and specificity of discography are matters of debate. Pressure-controlled discographies have been reported to reduce the number of false-positive discs using low pressure criteria. Preliminary data indicated a transfer of pressure from an injected to an adjacent disc during discography. Pressure transmission in vivo during lumbar discography, not reported before might, if clinically present, contribute to a false-positive diagnosis.

Thirty-six lumbar discs in 9 adolescent pigs were investigated. Intradiscal pressure was recorded during contrast injection, using a 0.36/0.25 mm fiber-optic pressure transducer inserted into the nucleus pulposus via a 22 G needle. The pressure was measured simultaneously in 2 adjacent discs during contrast injection into 1 of the discs at pressures up to 8 bar. Transmitted pressure was recorded both in noninjected discs and in discs that were prefilled with contrast.

Thirty-three discs were successfully examined. During contrast injection, there was an intradiscal pressure rise in the adjacent disc with a median value of 16.0% (range, 3.2-37.0) over baseline pressure. There was no significant difference in pressure increase between the noninjected and prefilled discs (P < 0.68).

Discography of porcine discs induces a pressure increase in adjacent discs. A similar pressure transfer during human clinical discography might elicit false-positive pain reactions.