Abstract:[Objective] To investigate the clinical outcomes of cortical bone trajectory (CBT) screw fixation for adjacent segmental de- generation (ASD) secondary to lumbar instrumented fusion. [Methods] From March 2018 to March 2019, a total of 20 patients underwent CBT screw fixation for ASD after primary instrumented fusion in our department. The clinical and imaging documents were summarized. [Results] All the 20 patients were successfully operated on without serious complications such as vascular and nerve injury, while with operative time of (1.44±0.31) hours, the intraoperative blood loss of (248.27±16.51) ml, and the postoperative ambulation time of (7.23±1.12) days. The postoperative follow-up lasted for (14.62±5.84) months on an average, and the VAS score significantly decreased from (8.70±1.30) pre- operatively to (1.81±0.27) at the latest follow- up (P＜0.05) , the JOA score significantly increased from (12.04±1.31) before operation to (23.84±2.91) at the latest follow-up (P＜0.05) , whereas the ODI index significantly decreased from (18.14±6.42) % before operation to (3.74± 0.55) % at the last follow-up (P＜0.05) . By the time of the last follow-up, all 18 patients had obtained interbody fusion with the fusion time ranged from 6 to 9 months. [Conclusion] The CBT screw fixation does achieve good clinical outcomes for treatment of ASD after lumbar in- strumented fusion.