Abstract:[Objective] To compare the clinical efficacy of posterior endoscopic decompression versus open extended posterior lumbar interbody fusion (PLIF) for adjacent segment diseases after lumbar fusion. [Methods] A retrospective study was performed on 26 patients who underwent surgical treatment for adjacent segment diseases after lumbar fusion in our hospital from January 2017 to January 2020. According to the results of doctor-patient communication preoperatively, 12 patients were treated with posterior endoscopic decompression (the endoscopic group), while the remaining 14 patients received PLIF (the PLIF group). The perioperative period, follow-up and imaging data were compared between the two groups. [Results] All the patients in both groups had operations performed successfully without serious complications. The endoscopic group proved significantly superior to the PLIF group in terms of operation time, incision length, intraoperative blood loss and hospital stay (P<0.05) . All patients in both groups were followed up for more than 12 months, and the endoscopic group resumed full weight-bearing activity significantly earlier than the PLIF group (P<0.05) . The low back pain VAS, leg pain VAS, ODI and JOA scores improved significantly over time in both groups (P<0.05) . At any corresponding time points, there was no significant difference in the above items between the two groups (P>0.05) . Radiographically, at the last follow-up, the spinal canal area and sagittal diameter of lateral recess significantly increased in both groups compared with those preoperatively (P<0.05) , while the lumbar lordosis angle remained unchanged (P>0.05) . Although there was no significant difference in the above indexes between the two groups before operation (P>0.05) , at the last follow-up , the endoscopic group proved significantly inferior to the PLIF group in the spinal canal area and sagittal diameter of lateral recess (P<0.05) , while there was no significant difference in lumbar lordosis angle between the two groups (P>0.05) . [Conclusion] The posterior endoscopic decompression has the advantages of quite less trauma and faster postoperative recovery for treating adjacent segment disease, and it achieves the similar clinical outcome as open extended PLIF.