The CHARITE Artificial Disc: design history, FDA IDE study results, and surgical technique.

INTRODUCTION Lumbar fusion serves to eliminate abnormal motion and instability at symptomatic degenerated levels, subsequently reducing or eliminating low back pain in patients with degenerative disc disease (DDD). Reported clinical outcomes for these procedures vary widely. A meta-analysis of lumbar fusion procedures performed by Geisler et al.10 demonstrated the elimination of lumbar segmental motion that resulted in a significant reduction in pain and subsequent improvement in disability level. Fusion is successful in many cases because the abnormal motion itself is the root cause of pain. When the segment is fused, it no longer moves and cannot, therefore, cause pain. Fusion, however, can result in stress and increased motion in the segments adjacent to the fused level, as demonstrated by Cunningham et al.6 This may initiate and/or accelerate the degenerative disease process in adjacent segments. Reported rates of adjacent-level disease requiring reoperation after lumbar fusion range from 20 to 35%.11,12 The inherent problem with surgical arthrodesis of the degenerative lumbar segment is that it merely masks the true disease process by eliminating the intervertebral motion and its normal physiological function.