Past, present, and future of cervical arthroplasty.

Cervical arthroplasty was developed in an attempt to maintain cervical motion and potentially to avoid or minimize adjacent-segment degeneration. If cervical arthroplasty is successful, the long-term results of surgery for cervical disc disease should improve. However, problems associated with cervical arthroplasty have been reported: these include kyphosis, heterotopic ossification-induced motion limitation, no motion preservation even at the index level, and a higher revision rate in a limited number of cases compared with anterior cervical discectomy and fusion (ACDF). In addition, for degenerative cervical disc disorders, the risk of developing adjacent segment degeneration more than 2 years after surgery is reportedly similar for ACDF and cervical arthroplasty. Cervical disc arthroplasty is an emerging motion-sparing technology and is currently undergoing evaluation in many countries as an alternative to arthrodesis for the treatment of cervical radiculopathy and myelopathy. The decision whether to use arthrodesis or arthroplasty is a difficult one. The achievement of good prosthetic performance demands exacting implantation techniques to ensure correct placement. This fact underlines the increasing importance of special instrumentation and surgical skills that involve an understanding of prosthetic lubrication, wear, and biologic effects and familiarity with currently available information regarding kinematics, basic science, testing, and early clinical results. Fortunately, a number of devices are at the late preclinical study stage or at the early clinical trial stage, and results in many cases are promising. In the near future, it is likely that new designs will be produced to replace spinal discs totally or partially in a pathologic entity-specific manner.