Neurological complications of lumbar artificial disc replacement and comparison of clinical results with those related to lumbar arthrodesis in the literature: results of a multicenter, prospective, randomized investigational device exemption study of Charité intervertebral disc

abnormalities and degeneration in the intervertebral disc. The associated pathological entities include herniation of the nucleus pulposus, DDD, and segmental instability. In recent years, the diagnostic accuracy and description of these abnormalities have been aided by the development of water-soluble myelography, MR imaging, provocative discography, diagnostic blocks, and high-resolution CT scanning techniques with administration of both intravenous and intrathecal contrast. During the past 20 years, multiple therapeutic advances have been made to aid in the surgical management of lumbar DDD. These advances include rigid segmental pedicle screw fixation, titanium and polymer interbody cage fusion, and fusion involving preprocessed allograft interbody spacers. In addition to instrumentation and fusion devices, osteobiological materials have been developed to reduce or elim-