Lumbar Intervertebral Disc Herniation: Annular Closure Devices and Key Design Requirements

Abstract

Lumbar disc herniation is one of the most common degenerative spinal conditions resulting in lower back pain and sciatica. Surgical treatment options include microdiscectomy, lumbar fusion, total disc replacement, and other minimally invasive approaches. At present, microdiscectomy procedures are the most used technique; however, the annulus fibrosus is left with a defect that without treatment may contribute to high reherniation rates and changes in the biomechanics of the lumbar spine. This paper aims to review current commercially available products that mechanically close the annulus including the AnchorKnot^® suture-passing device and the Barricaid^® annular closure device. Previous studies and reviews have focused mainly on a biomimetic biomaterials approach and have described some mechanical and biological requirements for an active annular repair/regeneration strategy but are still far away from clinical implementation. Therefore, in this paper we aim to create a design specification for a mechanical annular closure strategy by identifying the most important mechanical and biological design parameters, including consideration of material selection, preclinical testing requirements, and requirements for clinical implementation.

Keywords: annular closure device; design specification; intervertebral disc; lumbar IVD herniation.

Figure 1

Intervertebral disc structure (IVD). (Left) The spine within the body containing the vertebrae (bone) separated by IVDs. (Middle) Sectional view of the IVD. (Right) Cutaway view of the IVD showing the angle-ply structure of the annulus fibrosus, adapted from [6].

Figure 2

Commercial mechanical annular closure devices. (Top) Inclose Surgical Mesh System and the Xclose Tissue Repair System (Anulex Technologies, Inc. Minnetonka, MN, USA) [27]. (Middle) The AnchorKnot^® suture-passing device (Anchor Orthopedics XT Inc., Mississauga, ON, USA [31]. (Bottom) The Barricaid^® Annular Closure Device (Intrinsic Therapeutics, Woburn, MA, USA) [58].