The Posterior Epidural Ligaments: A Cadaveric and Histological Investigation in the Lumbar Region

Purpose. Incidental durotomy is a relatively common complication for patients undergoing posterior spinal surgery. Delineating anatomical variants in the posterior lumbar spinal canal is crucial in reducing future rates of incidental durotomy. Materials and Methods. The ligamentous attachments between the dura mater and ligamentum flavum in the lumbar region of 17 soft-fixed cadavers were investigated. The lumbar vertebral columns were removed, and cross-sectional dissection was performed at levels L1-S1. Anterior retraction of the dorsal dura mater identified attachments between the dorsal surface of the dura mater and the ligamentum flavum. Histological staining of the ligamentous attachments was carried out with hematoxylin and eosin (H&E) and elastic van Gieson (EVG). Results. Posterior epidural ligaments were present in 9 (52.9%) cadavers. Nine (9) separate ligaments were identified in these cadavers, with 3 (33.3%) at L3/L4, 5 (55.5%) at L4/L5, and 1 (11.1%) at L5/S1. Histology confirmed the presence of poorly differentiated collagen-based connective tissue, distinct from the normal anatomy. Conclusions. This study confirms the presence of multiple dorsomedial posterior epidural ligaments at the main sites for posterior spinal surgery (L3-S1). An intraoperative awareness of the variability of such connections may be an important step in reducing static rates of incidental durotomy. 1. Introduction Low back pain is a highly prevalent complaint, reported to affect 26.4% of US adults at some point in the last three months [1], although fewer than 1% of patients proceed to undergo surgical intervention [2]. In spite of methodical advances in surgical techniques, incidental durotomy (iatrogenic dural tears) during posterior spinal surgery still occurs. Incidental durotomy or iatrogenic dural tears remain a relatively commonplace and potentially serious complication of lumbar spine surgery [3–5]. Delineating anatomical variants in the posterior lumbar spine may be crucial in reducing future rates of incidental durotomy. The aim of this study was to investigate variations in the anatomical and histological features of the posterior epidural ligaments, passing between the dura mater and the ligamentum flavum in the lumbar spine. 2. Materials and Methods Seventeen lumbar spines were dissected from randomly selected soft-fixed cadavers with no known history of spinal disease or spinal surgery. Cross-sectional anatomical dissection at the levels L1-S1 via a dorsal approach was performed. Anterior retraction of the dura mater identified any connection between