Abstract:[Objective]To investigate the mid-term results of percutaneous endoscopic lumbar discectomy (PELD) in terms of clinical and radiographic findings and complication incidence.[Methods] Clinical data were retrospectively analyzed and a total of 42 cases were followed up.From January 2012 to June 2013, there were 24 males and 18 females, aged 17-73 years, with an average age of 48.5 years, 37 patients with lumbar intervertebral disc herniation, 5 patients with lumbar spinal stenosis, 21 patients with single segmental disc herniation L4-5, 11 patients with L5-S1, and 5 patients with multiple segmental disc herniation.There were 40 cases of protrusion type and 2 cases of prolapse type.There were 32 cases of paracentral type, 8 cases of central type and 2 cases of lateral type.Patients with lumbar spinal stenosis and multiple segmental disc herniation underwent preoperative selective nerve root block to confirm the responsible segment.All patients underwent PELD in prone position.Postoperative rehabilitation were performed.The straight leg raising test(SLR) angle, visual analog scale(VAS) scores for the back and legs (VAS-B and VAS-L, respectively), JOA score, Oswestry disability index (ODI), and Mcnab were evaluated at preopration, 6 months postoperatively and the final follow-up.Height of intervertebral space and dynamic position were measured with X-ray, and the final follow-up was compared with operation.[Results] The follow-up period was 72-90 months, with an average of 82±5.5 months. For SLR,VAS-B,VAS-L,JOA,ODI, the results of 6 months and final follow-up were compared with preoperation respectively,the differences were both statistically significant (p<0.01).Comparison between 6 months and the final follow-up showed statistically significant differences in ODI (p<0.05), and no statistically significant differences in the remaining evaluation indexes (p>0.05)..According to the Mcnab evaluation criteria, the excellent and good rates were 83.3% at 6 months postoperatively and 84.2% at the final follow-up, the differences were both statistically significant (p<0.01).The mean odds ratio of disc height between the final follow-up and preoperation was 84.52±5.66%, and the sign of lumbar instability was not shown in the dynamic position measurement.Postoperative infection, dural tear and nerve root injury were not found in this group of patients.The incidence of postoperative numbness in the innervation area of nerve roots was 14.3% at 6 months and 4.8% at 6.8 years after surgery.Two patients (4.8%) underwent revision within 3 months after surgery.[Conclusion] The short-term effect of PELD with lateral approach is good, and the mid-term effect remains good after more than 6 years of follow-up. The incidence of complications and recurrence are similar to that of open lumbar microdiscectomy, and no significant effect on lumbar stability is shown.