A historical review and current perspective on the intervertebral disc prosthesis.

Spinal fusion for degenerative disc disease has been associated with a variety of side effects, including increased morbidity, infection, failed back syndrome, pseudoarthrosis, and acceleration of degenerative changes in adjacent intervertebral discs and facet joints. Based on the experience of arthroplasty of hip and other joints, there has been an escalating in research emphasizing the design and development of an artificial disc prosthesis. However, these artificial discs have not been very successful when compared with hip or knee replacements. Based on clinical and anatomical data, multiple authors have postulated that the degenerative process of intervertebral disc evolves through three stages; dysfunction, instability and stabilization, with relatively distinct clinical and radiological findings. Even though magnetic resonance imaging is considered as the primary diagnostic tool for degenerative disease, it is unable to reliably ascertain which disc level is responsible for generating axial pain symptoms. Consequently, discography is the most precise test to localize the level of pathology. Multiple design criteria have been proposed for an ideal intervertebral prosthesis which included endurance, materials behavior, geometry, kinematics, dynamics, motion constraints, fixation to bones and safety. The development of artificial disc technology has culminated into two types of disc replacements, namely total disc replacement and a nucleus pulposus replacement. In addition, four prosthetic models have been proposed which include hydraulic, elastic, composite, and mechanical. Clinical outcomes of total disc replacement and nucleus replacement have been variable. This review describes natural history of disc disease and the diagnostic process, anatomical and biomechanical considerations, design criteria for an ideal intervertebral prosthesis, evolution of artificial disc prosthesis, clinical outcomes of the total disc and nucleus replacement, and prospects and meridians for future research.