Motion preservation technologies: alternatives to spinal fusion.

Spinal arthrodesis is a versatile and effective option in the management of instabilities, deformities, and painful spinal conditions. An increasing body of biomechanical and clinical evidence suggests that the relative immobility of fused spinal segments alters stress transfer, leading to adjacent-level degeneration. The development of nonfusion spinal prostheses has been driven by increasing concerns regarding these arthrodesis-related morbidities, including graft-site harvest, pseudarthrosis, and adjacent-level degeneration. Motion-sparing implants offer some theoretical advantages over fusion; however, judicious use of these products with careful patient selection is warranted until outcome studies can demonstrate their efficacy. In this article, we review the 3 major categories of nonfusion technologies: total disc replacement, prosthetic nuclear implants, and posterior stabilization devices.