Objective      To evaluate the clinical value of hybrid dynamic stabilization with posterior spinal fusion (a topping-off surgery) in treatment of lumbar degenerative diseases by comparing with that of single-level fusion.       Methods      Twenty seven patients with preoperative adjacent segment degeneration were given hybrid dynamic stabilization with posterior spinal fusion (topping off surgery

TOS group)

and 30 patients without preoperative adjacent segment degeneration were given singlelevel fusion (SLF group). The clinical efficacy was evaluated and compared by visual analogue scale (VAS)

Oswestry disability index (ODI)

range of motion (ROM) of global lumbar spine

ROM of adjacent segments

intervertebral space ratio (ISR)

ROM of index level (the level dynamically stabilized by Isobar)

and the incidence of adjacent segment degeneration (ASDeg).       Results      All the patients were followed up for 12-40 months. VAS and ODI score were significantly improved in both two groups

but the difference between the two groups was not significant. The ROM of global lumbar spine was not significantly different between the two groups at the last follow-up. The ISR of index level was not significantly different before operation and at the last follow-up. The ROM of first cranial adjacent segment increased significantly at the last follow-up in both two groups. No progression of degeneration was observed in the index levels during the follow-up. Adjacent segment instability was observed in 7 patients of the TOS group and 5 patients of the SLF group

  the incidence of adjacent segment instability was no significant difference between the two groups. Looseness or breakage of fixation system was observed in two patients of the TOS group.       Conclusion      Hybrid dynamic stabilization with posterior spinal fusion achieves satisfying clinical efficacy during early follow-up

but the incidence of fixation system failure may be higher  than the single-level fusion

suggesting selection of appropriate indications is important for achieving good clinical efficacy.