Background Standard microscopic lumbar discectomy (MLD) is a short operation with minimal blood loss, and a low rate of peri- and intraoperative complications. The objective of this study was to evaluate intraoperative findings, complications, and early postoperative neurological outcome (< 105 days) in patients undergoing MLD with or without implantation of an annular closure device (ACD). Methods This study is based on data analysis of a post-marketing, prospective, multicenter RCT in Europe including patients undergoing standard MLD with or without implantation of an ACD (Barricaid®, Intrinsic Therapeutics, Inc., Woburn, MA). Enrollment of 554 patients in 21 centers in Europe (Germany, Switzerland, Austria, Belgium, The Netherlands, and France) started in 2010 and was completed in October 2014, with 276 patients randomized to the ACD group and 278 to the control group. Results Mean operation time was 70 min in the ACD group and 52 min in the control group (p < 0.0001). Intraoperative fluoroscopy time was 24 s in the ACD group and 7 s in the control group (p < 0.0001). Average blood loss was 94.2 ml in the ACD group and 64.7 ml in the control group (p = 0.0001). Serious device- or procedure-related adverse events occurred in 3.7% (10/272) of the ACD group and 7.9% (22/278) of the control group. Dural injuries occurred in 13 (4.8%) patients in the ACD group and 7 (2.5%) in the control group. There was one device-related nerve root injury resulting in a nerve root amputation. Surgical complications included 3 hematomas in the ACD group and 4 in the control group; 3 infections occurred in both groups. Device migrations were documented in 3 patients in the ACD group. Patients in the ACD group (n = 7, 2.6%) underwent fewer reoperations compared with that in the control group (n = 16, 5.8%, OR = 2.3 (0.9–5.7)). Mean VAS leg pain at 3 months was 11.9 in the ACD and 15.1 in the control group, respectively. Conclusion Short-term outcome after MLD with or without implantation of ACD was similar in both groups. Patients included in the ACD group underwent fewer reoperations in the first 3 months after surgery. Nevertheless, longer operation time, higher amount of blood loss, and risk of nerve root lesion during device implantation should be considered additional risks in patients undergoing ACD implantation after MLD.