Simon Harris, MA, MB, BChir, FRCSC, Orthopaedic Spine Surgeon, Trillium Health Partners, Mississauga, Ontario.

Abstract
Degeneration of the cervical discs is a common problem and can cause compression of cervical nerve roots and/or the spinal cord. This in turn may lead to permanent neurological injury, disability and socioeconomical impact for the patient. Surgical management typically includes either an Anterior Cervical Decompression and Fusion (ACDF) or a Posterior Decompression with or without fusion or laminoplasty. Over the past 20 years, Cervical Disc Arthroplasty (CDA) has been an increasingly viable alternative to the “Gold Standard” ACDF, after failure of conservative management in the appropriately selected patient. Single and multilevel CDA has a growing body of evidence to support its equivalency - and even superiority - to ACDF in long-term clinical outcomes.
Key Words: Cervical degenerative disc disease; Cervical Disc Replacement; Cervical Disc Arthroplasty; Radiculopathy; Myelopathy.

Introduction
Cervical disc degeneration is a frequent problem, predominantly impacting the aging demographic. The degenerative process, affecting both symptomatic and asymptomatic individuals, underscores the complexity of the aging cervical spine. While conservative management remains the cornerstone for axial neck pain, symptoms due to impingement on neurological structures may require surgical intervention. Among the evolving array of surgical options, Cervical Disc Arthroplasty (CDA) has gained prominence, offering a motion-sparing alternative to the traditional Anterior Cervical Discectomy and Fusion (ACDF). This article discusses the pathogenesis and sequalae of cervical disc degeneration, explores the history of CDA, delineates the criteria for surgical candidacy, and reviews the evidence supporting its efficacy.

Cervical Disc Degeneration
Degeneration of the cervical discs is an inevitable progression affecting the aging population. The degenerative process begins with dysfunction such as annular tears, progresses to instability with disc herniation and/or resorption of the nucleus pulposus, which can then lead to restabilisation with bone hypertrophy and ankylosis.¹ Degenerative changes occur in both symptomatic and asymptomatic individuals. Surgery on the cervical spine may be required when the degenerative process leads to symptomatic impingement of either the cervical spinal cord and/or the exiting nerve roots. The mid to lower cervical discs have a greater range of motion and so are predisposed to earlier degeneration. C5/6 and C6/7 are the most common levels involved.