Editor’s preface: the science of intervertebral disc replacement

Excerpt

Total disc arthroplasty (TDA) has evolved into an extremely exciting technology over the last decade. After the initial enthusiasm, some disillusion has also spread, because the long-term results are not as good and reliable as hoped, and it has become evident that the development of an artificial disc is a big challenge [1‐3]. Nevertheless, the number of disc prosthesis products on the market has grown rapidly in the recent years. Until now, many proposed solutions are fairly simple, compared to a real intervertebral disc, which has a very complex structure [4‐6]. Most of the current designs are based on an articulating ball-and-socket concept, reminiscent of the conventional implant systems that we already know from other joints. The various prosthesis designs attempt to control the movement directly by the geometry of the articulating surfaces, to mimic the physiological centre of rotation or to allow a fully unconstrained motion of the individual prosthesis components in devices with mobile cores. The current trend for disc implants is to design them in such a way that the three-dimensional physiological stiffness of the natural disc is reproduced. Therefore, the types of prostheses, which are currently available can be distinguished between implants with a fixed centre of rotation, incompressible prostheses with a mobile centre of rotation, and compressible prostheses with a mobile centre of rotation. …