The Use of PEEK in Spine Arthroplasty

Abstract

Cervical and lumbar disc arthroplasty are one component in the continuum of treatment for symptomatic degenerative disc disease (DDD) that is unresponsive to conservative care. In the lumbar spine, this may be accomplished via nucleus replacement or total disc replacement, and in the cervical spine by total disc replacement. The goal of both lumbar disc arthroplasty treatments are the same; relieving discogenic back pain through removing the pain source and restoring or maintaining motion segment function. For cervical arthroplasty, the goal is to relieve radicular pain as a result of nerve root compression, and/or myelopathy as a result of spinal cord compression, in addition to preserving motion. From a design standpoint, nucleus replacement technology consists of elastomers and nonelastomers, both preformed and in-situ cured, and can incorporate articulation similar to total disc replacements, with the intent of replicating to various extents the natural nucleus and preserving most of the annulus, thereby relying on a biomechanically intact annulus to share the compressive load. Also, most artificial nucleus devices are not fixed to the vertebral endplates, and therefore allow small, relative motion between their external surfaces and the vertebral endplates. In contrast, the majority of total disc replacement technology consists of articulating designs and material combinations that have been developed based upon the wealth of scientific and clinical information produced by the success of total joint arthroplasty. An artificial disc is designed to replace the entire disc tissue by excising almost all the disc materials, and therefore removing all the natural constraints in the anterior column. In addition, all artificial discs have a superior plate and an inferior plate, which are fixed to the two adjacent vertebrae. These represent key design differences between the two technologies. A key challenge for a disc arthroplasty device is selecting the proper material(s) for the various components that consitute its design. Unlike total joint replacement, a candidate for disc arthroplasty is on average 40 years of age with a target indication of 18 to 60 years (Zigler et al., 2007; Murrey et al., 2009). As a consequence, these devices are expected to last much longer than those of total joint recipients, whose average age is 70 years (Bergen, 2011, Garellick et al., 2010). Therefore, there are stringent requirements for long term implantable materials, and this will significantly limit the selection of materials available. Biocompatibility and biodurability, otherwise known as the abilities of a material to maintain its physical and chemcial integrity under in vivo applications without eliciting an aggressive host immune response for a given application, are essential for permanent