Normal and abnormal imaging findings in lumbar total disk replacement: Devices and complications

Fusion, with or without laminectomy, is the standard treatment for symptomatic lumbar degenerative disk disease when conservative management has failed. Yet even radiographically verified solid fusion may be accompanied by considerable long-term problems, including recurrent low back pain, spinal stenosis, hypertrophic facet disease, pseudarthrosis, and spondylolysis and spondylolisthesis at adjacent levels. Several studies have shown a relationship between solid fusion and the development of adjacent-level disk disease, which is thought to result from increased stress on, or hypermobility of, adjacent seg-ments. Total disk replacement (TDR) was developed as a way to re-store normal mobility of the diseased segments and improve clinical outcomes by decreasing the risk of adjacent-level degenerative disease and related complications. However, like fusion, TDR is associated with various complications; some of these (eg, migration, subsidence) may occur regardless of the device used, whereas others (eg, extru-sion of the polyethylene inlay, vertical fractures) are device specific. Facet arthrosis, device wear, particle disease, adjacent-level degenera-tion, and heterotopic ossification also have been observed after TDR, but the frequency and importance of these findings remain uncertain. Given the increasing use of lumbar TDR to treat degenerative disk disease, it is important that radiologists be familiar with the most com-monly used devices and the potential complications of their use.