An AOA Critical Issue

Abstract

Intervertebral disc replacements have been under design for over three decades but are now receiving increased attention. This is largely due to several devices that have received Investigational Device Exemption status from the United States Food and Drug Administration, resulting in clinical trials in the United States. There is tremendous early enthusiasm for the concept of disc replacement and motion preservation as an alternative to arthrodesis, with the hope that adjacent segment degenerative changes can be averted. Skeptics hold the position that adjacent segment changes are due more to the individual's genetic predisposition and normal aging than to the mechanical changes resulting from a spinal arthrodesis. In addition, there are potential long-term consequences to disc replacement that remain unknown. These issues include failure, wear debris, and the effects of stress-risers as patients age and become osteopenic. The two basic categories of disc replacements are nuclear replacements and total disc replacements. The critical issues pertaining to total disc replacements were recently explored in a symposium at the 2003 Annual Meeting of the American Orthopaedic Association in Charleston, South Carolina, and are summarized in this review. The vast majority of patients with degenerative disc disease are managed with nonoperative methods, including analgesic and anti-inflammatory medication, muscle strengthening, weight control, and aerobic training. Management with injection of corticosteroids may also be attempted. With these modalities, the results are generally good. Surgical management has been reserved for the patients in whom these treatment options have failed. Numerous authors have reviewed the complications and failures of spinal arthrodesis in the low back1,2. The purpose of this discussion is not to list and comment on all of the difficulties with an invasive approach but to focus on the difficulties that may be alleviated or ameliorated by a stable disc arthroplasty. The first …