Authors: Claudius Thome, MD, IFAANS; Javier Fandino, MD; Peter Klassen, MD; Frederic Martens, MD; Anular Closure RCT Study Group (Innsbruck, Austria)

Introduction: Recurrent disc herniation and reoperation are a major concern following lumbar microdiscectomy associated with worse clinical outcomes and greater socioeconomic burden. Patients with large annular defects are known to be at high risk for reherniation. This study aimed at determining whether a bone-anchored annular closure device (ACD) in addition to lumbar microdiscectomy resulted in lower reherniation and reoperation rates plus increased overall success in these patients. Methods: In this randomized, prospective, multicenter trial primary microdiscectomy patients at 21 sites were randomized intraoperatively 1:1 to microdiscectomy alone (Control; n=278) or microdiscectomy supplemented with the ACD (n=272). Key inclusion criteria consisted of a minimum of 5mm posterior disc height and an intraoperatively measured annular defect width of 6-10mm. Kaplan-Meier survival analyses were used to evaluate freedom from symptomatic reherniation, reoperation, and severe adverse events (SAEs). Clinical overall success was defined post hoc as freedom from reherniation/reoperation, >15-point improvement in ODI, >20-point improvement in VAS, maintenance of neurological status and freedom from SAEs. Log-rank tests were used for group comparisons. Results: At 3 years >80% of patients were available for follow-up. Symptomatic reherniations had occurred in 14.8% of the ACD group and 29.5% among Controls (p<0.0001). At least one reoperation, for any reason including device complications, was required in 11.0% and 19.3% of patients in the ACD and Control groups, respectively (p=0.007). Device- or procedure-related SAEs occurred in 10.0% of ACD patients and 19.3% of Controls (p=0.002). 69.9% of ACD patients demonstrated a successful outcome compared to only 55.7% of Controls (p=0.003). Conclusion: The subpopulation of microdiscectomy patients with large annular defects is characterized by a very high risk for reherniation. Adding an ACD at the time of microdiscectomy in these patients significantly lowers the risk of symptomatic recurrence and reoperation plus improves overall clinical success through 3 years of follow-up.