Long-term Follow-up (Minimum 5 Years) Study of Single-level Posterior Dynamic Stabilization in Lumbar Degenerative Disease; 'Interspinous U' & 'DIAM'.

Objectives: Recently posterior dynamic stabilizations (PDS) are increased in degenerative lumbar disease. But, some previous studies had doubts its long term prognosis. Long term clinical and radiological results of PDS using interspinous device (Interspinous U, DIAM) were analyzed.

Methods: We have used the 'interspinous U' and 'DIAM' for patients with lumbar spinal stenosis. We included single level lumbar spinal stenosis patients who completed minimum 60 months follow-up evaluation. All patients checked plain lateral and flexion-extension views at immediately after the surgery and each follow-up. The clinical outcome was measured by Odom's criteria. Complications including post operative infection, bony erosion, device fracture, device malformations, and instabilities were surveyed.

Results: We included 18 for 'Interspinous U' and 7 patients 'DIAM' groups. Mean follow-up durations for 'Interspinous U' and 'DIAM' were 74.6 and 62.6 months, respectively. Satisfactory groups were 50.0% and 42.9 % for 'Interspinous U' and 'DIAM' groups. In 'Interspinous U' group disc height ratio increased transiently in immediate postoperative period (from 0.18 to 0.21) and then, decreased significantly in last follow-up (0.18). In 'DIAM' group, disc height ratio increased transiently in immediate postoperative period (from 0.18 to 0.19), and then decreased significantly in the last follow-up (0.16). Three (16.7%) and two (28.6%) patients undergo on a re-operation due to severe back pain in 'Interspinous U' and 'DIAM' groups.

Conclusion: Long term follow up 'Interspinous U' and 'DIAM' group showed low patient satisfaction and poor radiological outcomes. To ascertain the benefit of PDS compare with posterior screw fixation, prospective analysis with larger population and multi-center study will be needed.