Factors influencing manometric pressure during pressure-controlled discography.

Abstract

In vitro laboratory study. The aim of this study was to evaluate the effects of injection speed, contrast viscosity, and needle profile on manometric pressures during discography. As the degree of the response in a provocation test depends on the intensity of the stimulus, the precise measurement of intradiscal pressure during discography is crucial. Although manometric pressure measurement is safe and easy, manometric pressures may be affected by potential confounding factors, including injection speed, contrast viscosity, and needle profile. Pressure-controlled discography was performed using an automated pressure-controlled discography system in a total of 60 intervertebral discs in 2 porcine cadavers. Dynamic pressures were measured while changing the following parameters: injection speed (0.01 mL/s vs. 0.08 mL/s), media viscosity (Visipaque vs. normal saline), needle diameter (18G vs. 22G), and needle length (7 inch vs. 3.5 inch). The unit change in manometric pressure per fractional change in injected volume (dP/dV) was used for statistical analysis. The mean dP/dV increased from 137.9 +/- 11.3 at 0.08 mL/s to 160.3 +/- 12.5 at 0.01 mL/s. Visipaque injection resulted in a higher mean dP/dV than the normal saline injection (160.3 +/- 12.5 vs. 97.8 +/- 34.1). A 7.5 inch needle had a higher mean dP/dV than a 3.5 inch needle (137.9 +/- 11.3 vs. 92.5 +/- 48.6). The mean dP/dV of the 22G needle was higher than the 18G needle (137.9 +/- 11.3 vs. 84.7 +/- 28.3). High injection speed, high viscosity, small diameter, and a long needle increase the dynamic pressure. To minimize the differences among examiners, we recommend standardization of injection speed, the viscosity of the injected material, and the diameter and length of the needle.