Abstract: BACKGROUND: The treatment of adjacent spondylopathy after lumbar fusion is a research hotspot in spine surgery. Traditional surgery to extend the fusion segment may accelerate the reappearance of adjacent segment disease. The non-fusion pedicle screw system based on pedicle screws has shown excellent short- and mid-term results in the treatment of lumbar degenerative diseases and the prevention of adjacent segment degeneration. However, reports on the use of non-fusion technology to treat adjacent segment disease after lumbar fusion need to be studied urgently.  
OBJECTIVE: To assess the postoperative outcome of non-fusion dynamic stabilization in situ with the Isobar EVO System for adjacent segment disease.
METHODS:  Patients with adjacent segment disease who were re-operated at Dongzhimen Hospital from July 2013 to December 2017 due to ineffective conservative treatment were selected. Fifteen patients with adjacent segment disease who received Isobar EVO in situ non-fusion dynamic stabilization treatment were enrolled. Medical records, surgical reports, and X-ray imaging studies were reviewed. The following two groups of indicators were compared before and after operation: low back pain visual analogue scale score and lower limb pain visual analogue scale score, Oswestry Disability Index, SF-36 scale physical health score, range of motion of the operative segment, the motion of the upper adjacent segment, the lordotic angle of the operative segment and the angle of lumbar spine, the disc of height index at surgical segment, and the disc of height index at superior segment.  
RESULTS AND CONCLUSION: Fifteen patients completed at least 3 years of follow-up. (1) Clinical results: At the last follow-up, the scores were significantly improved compared with those before the operation (P < 0.05), but there was no significant difference between different periods of the follow-up (P > 0.05). (2) Imaging measurement: At the last follow-up, mean range of motion of the segment was significantly reduced compared with that before the operation [(3.16±0.45)° vs. (6.32±1.81)°, P < 0.05]; the average motion range of the superior segment was significantly increased compared with that before the operation [(5.51±1.22)° vs. (4.87±1.47)°, P < 0.05]. The lumbar lordosis angle was significantly increased compared with that before the operation [(30.95±8.96)°vs. (27.12±9.67)° , P < 0.05 ]; the lordosis angle of the operation segment was significantly increased than that before the operation [(11.32±4.86)° vs. (10.14±6.44)°, P < 0.05]. Disc of height index at surgical segment was significantly higher than that before the operation (33.23±3.83 vs. 32.79±4.06, P < 0.05). However, disc of height index at superior segment was not statistically different from preoperatively (P > 0.05). There was no statistically significant difference in above indexes between each period of follow-up after operation (P > 0.05). In all cases, there was no loosening of the internal body during the follow-up period, and no adjacent segment disease occurred again. (3) It is concluded that Isobar EVO non-fusion dynamic fixation is an effective way to treat adjacent segment disease, and the clinical effect is obvious. The follow-up results for more than 3 years after surgery show that this operation can prevent the occurrence of adjacent segment disease after reoperation to a certain extent. The long-term effect needs to be supported by the results of further follow-up and higher-level evidence-based medicine.

Key words: adjacent segment disease, reoperation, non-fusion, dynamic stabilization, Isobar EVO, lumbar vertebrae