While Provocation Lumbar Discography has been used to identify discs responsible for low back pain, the biomechanical effects of disc injection have received little attention. The purpose of this study was to assess the motion of the Functional Spinal Unit including the Endplate and Facet/Pedicle region during disc injection including comparison between normal and degenerative discs.
91 consecutive patients referred for Discography with chronic low back pain.
Lateral projection vertebral motion was retrospectively analyzed at 232 levels (normal: 76 (32.8%), degenerative: 156 (67.2%)). Pre and post injection fluoroscopic images were size-scaled and lower endplates superimposed on separate PowerPoint images. Upper Endplate and Facet/Pedicle motion was separately and independently analyzed on toggled PowerPoint images, subjectively graded as: Prominent, Intermediate, Questionable/Uncertain, or No Motion. Disc morphology was graded using the AP/Lateral post-injection disc appearance (Adams Criteria).
Prominent or Intermediate Endplate and Facet/Pedicle motion was identified at most lumbar levels with substantial overall agreement (degenerative: κ = 0.93; CI: 0.87-1.00, normal: κ = 0.80; CI: 0.61-1.00). Degenerative levels were strongly associated with a lower degree of Endplate and Facet/Pedicle motion compared with normal: (“Prominent” motion grade: Endplate: 61% (95/156) versus 89% (68/76) (p < 0.001), Facet/Pedicle: 60% (93/156) versus 88% (67/76) (p < 0.001)).
Disc injection expands the disc space inducing Endplate motion, Pedicle motion and Facet translation in almost all normal and most degenerate levels. Disc injection therefore biomechanically ‘Provokes’ the entire Functional Spinal Unit. When ‘Provoked’ pain is encountered during lumbar discography, contribution from the associated facet joint and myo-tendinous insertions should be considered.

© The Author(s) 2021. Published by Oxford University Press on behalf of the American Academy of Pain Medicine.