Endplate Changes after Discectomy and Implantation of an Annular Closure Device

Aim: Limited lumbar microdiscectomy (LMD) is the most commonly performed spine surgery associated with pain relief, low rate of complications, and a rate of reherniation between 3 and 18%. The aim of our study was to analyze the clinical and radiological outcome after LMD with additional implantation of the Barricaid annular closure device (ACD) to prevent reherniation.

Methods: The outcome evaluation included VAS for leg and back pain and ODI. Radiological findings included proof of reherniation, implant integrity, Smartbrush volumetry of endplate changes (EPC), and assessment of disc height and degeneration (Pfirrmann classification). In addition, several risk factors (smoking, sex, age, localization of the anchor) for the induction of EPC were examined in a multivariate multiple regression model. Influence of EPC on postoperative back and leg pain and ODI was assessed.

Results: Seventy-one patients (37 men, 47 ± 11.77 years old) operated between 2013 and 2016 were included. A total of 69 (98%) patients presented with EPC during the follow-up period (15.04 ± 4.73 months). The multivariate regression analysis led to the detection of the localization of the anchor as only significant predictor of EPC (p = 0.038). The localization in the cranial endplate relative to the vertebra leads to larger EPCs in the lower endplate of the adjacent vertebra (p = 0.025). In general, the EPC were larger in the lower endplate of the vertebra, with a mean of 0.476 cm³, compared with those in the upper endplate, with a mean of 0.180 cm³. The largest EPC was 4.18 cm³. Decreased in VAS was documented after surgery (p < 0.05): left leg pain (36.5), right leg pain (35.6), and low back pain (46.3). ODI score decreased by 41.3 points. Disc height decrease was observed (0.731 ± 0.6 mm, p > 0.5). The intraoperatively removed mean disc material was 1.343 cc, and the mean defect width 7.765 mm. Reherniation was radiologically documented in 17 (24%) patients (symptomatic: n = 10, 7%; asymptomatic: n = 7, 5%). Six (8.5%) patients with symptomatic reherniation underwent rediscectomy and four (5.7%) patients were conservatively treated. Implant failure was documented in 28 (40%) patients which included dislocation of the device (n = 5, 7%), dislocation of the mesh (n = 11, 16%), and mesh subsidence (n = 12, 17%). Seven (9.86%) patients underwent explantation of the whole or parts of the device.

Conclusion: Clinical improvement after limited LMD and ACD implantation was documented. Postoperative VAS and ODI scores significantly improved. Despite of the fact that EPC was observed in 98% of the patients, volume of EPC did not correlate with clinical outcome. Mechanical friction of the polymer mesh to the endplate might be the cause of EPC after implantation of the Barricaid ACD. Long-term clinical and radiological assessment are necessary to evaluate the consequences of these findings.