Mid-term evaluation of the effects of dynamic neutralization system on lumbar intervertebral discs using quantitative molecular MR imaging

Purpose: To evaluate the mid-term effects of implant of dynamic neutralization system (Dynesys) on disc tissue in patients with lumbar discopathy, through the quantifica- tion of glycosaminoglycans (GAG) concentration, both in treated and adjacent levels, by analysis of delayed gado- linium-enhanced MRI contrast (dGEMRIC) images. Materials and Methods: Ten patients with low back pain, underwent the dGEMRIC diagnostic protocol before, 6- months and after 2 years from surgery. Each patient was also evaluated with visual analog (VAS), Oswestry, and Prolo scales both at presurgery and during follow-up. From dGEMRIC images, a DT1 parametric map was obtained for each disc, as quantitative indicator of its GAG concentration, and divided in 13 sectors, which were classified at presurgery as normal or abnormal, based on a 70-ms threshold. Evolution of DT1 was studied during the follow-up. Results: Nine of ten patients completed the follow-up. VAS, Oswestry, and Prolo grades showed an improve- ment. This was accompanied by a reduction of DT1 in abnormal segments while normal segments showed a pat- tern of initial worsening at 6 months, followed by an improvement after 2 years. Conclusion: Our study confirmed the improvement in clinical evaluation, and for the first time related this to the changes in discs GAG concentration.