Posterior annular strains during discography

Discography is commonly used in the workup of back disorders. The clinical utility of the test is controversial, and little is known about mechanical changes that may occur in the disc during this exam. To quantify three-dime nsional deformations of the posterior annulus during discography. and to ex amine some of the covariates that influence the deformations, displacements of the lumbar posterior annulus were measured during discographic injectio n for three different spinal positions. Disc bulge and annular strains were calculated from the displacements. The combined effect of disc pressurizat ion, spine position, and location on the disc (lateral versus midline) expl ained much of the variation in the measured bulges and strains (r(2) = 0.56 ). Disc pressurization or spine position alone did not always have a signif icant effect on strains, and the strains and bulges were often influenced b y the interactions between position of the spine, location of the disc, and pressurization, In clinical studies of discography, these results suggest that patient position during the examination should be standardized.