Table 3 Introduction of a new classification of ACD associated EPC. The EPC score ranges from 1 to 4 and assesses anchor localization (superior/inferior) and size of EPC (< 1cm³ / > 1cm³) as criteria. Scores were defined as follows: grade 1 includes patients with ACD implanted on inferior EP and EPCs of < 1 cm³, grade 2 have an ACD in the superior EP and EPCs < 1 cm³, grade 3 received ACD in inferior EP and EPCs > 1 cm³, and finally maximum grade 4 if ACD is in the superior EP and the EPCs are > 1 cm³. ACD = Annular closure device

From: Incidence and clinical impact of vertebral endplate changes after limited lumbar microdiscectomy and implantation of a bone-anchored annular closure device