Abstract:[Objective] To compare the clinical outcomes of unilateral biportal endoscopic (UBE) decompression of the responsible segment versus posterior lumbar interbody fusion (PLIF) for degenerative spinal stenosis in the elderly. [Methods] A retrospective study was performed on 65 patients who underwent surgical treatment for lumbar spinal stenosis in our hospital from January 2018 to March 2021. According to doctor-patient communication, 28 patients received UBE decompression, while the other 37 patients received PLIF. The perioperative, follow-up and imaging results were compared between the two groups. [Results] Although there was no significant difference in operation time between two groups, the UBE group was suprior to the PLIF group in terms of total incision length [(2.1±0.9) cm vs (11.2±1.12) cm, P<0.05], intraoperative fluoroscopy times [(3.3±0.8) vs (5.9±1.2) times, P<0.05], intraoperative blood loss [(36.2±10.2) ml vs (201.3±11.3) ml, P<0.05], ambulation time [(22.7±5.1) days vs (40.2±8.5) days, P<0.05] and hospital stay [(7.3±2.2) days vs (11.2±3.0) days, P<0.05]. The mean follow-up period lasted for (14.1±1.1) months, and the UBE group resumed full weight-bearing activity significantly earlier than the PLIF group [(4.3±2.8) weeks vs (10.6±3.4) weeks, P<0.05]. The VAS scores for low back pain and leg pain, as well as ODI scores significantly improved in both groups over time postoperatively (P<0.05), which was not statistically significant between the two groups before surgery (P>0.05). The UBE group was significantly better than the PLIF group regarding low back pain VAS score [(2.3±0.7) vs (2.8 ±0.9), P<0.05], leg pain VAS score [(2.5± 0.6) vs (2.9±0.7), P<0.05], and ODI score [(20.6±3.3) vs (23.4±2.9), P<0.05] 3 months postoperatively, while which became not statistically significant between the two groups at latest follow up (P>0.05). Regarding imaging, the lateral recess diameter and spinal canal cross-section significantly increased in both groups at the last follow-up, compared with those before surgery (P<0.05), the lumbar scoliotic Cobb angle remained unchanged significantly in the UBE group (P>0.05), but decreased significantly in PLIF group (P<0.05). There were no significant differences in lateral recess diameter, vertebral canal cross-sectional area and scoliotic Cobb angle between the two groups before surgery (P>0.05), however, the PLIF group got significantly less scoliotic angle than the UBE group at the latest interview [(15.7±3.3)° vs (17.8±4.6)°, P<0.05]. [Conclusion] The unilateral biportal endoscopic decompression of the responsible segment has benefits of less trauma and better short-term clinical consequences over the traditional open PLIF for degenerative lumbar spinal stenosis in the elderly.