Cervical Disk Arthroplasty Versus ACDF for Preoperative Reducible Kyphosis

Cervical total disk arthroplasty has proven to be an effective and safe alternative for anterior cervical diskectomy and fusion (ACDF) for the treatment of cervical disk degenerative disease. However, whether and when cervical disk arthroplasty is indicated for preoperative cervical spine kyphosis is unclear. In the authors' clinical experiences, preoperative kyphosis can generally be divided into reducible and irreducible forms according to the results of dynamic flexion-extension lateral radiographs. Reducible kyphosis is mostly related to local disk prolapse, clinical symptoms, and musculature weakness, but irreducible kyphosis is always associated with significant cervical degeneration or congenital bone malformation. In this study, 32 patients with preoperative reducible kyphosis were randomized in a 1:1 ratio to either single-level total cervical arthroplasty with the Discover cervical disk prosthesis (DePuy Spine, Raynham, Massachusetts) (arthroplasty group) or single-level ACDF with a polyetheretherketone cage and plate (ACDF group). No significant differences existed in clinical and radiological results at 2-year follow-up between the arthroplasty and ACDF groups. The global and functional spinal unit angles of the arthroplasty group were significantly lower than those of the ACDF group 6 months postoperatively, which was consistent with the result of the comparison in Neck Disability Index score. However, the sagittal alignment of the overall cervical spine and the treated segment and the Neck Disability Index score significantly improved after 6 months in the arthroplasty group but not in the ACDF group. Therefore, preoperative reducible kyphosis is not a contraindication for cervical total disk arthroplasty. However, neck strength-building exercises should be emphasized for the postoperative rehabilitation after cervical total disk arthroplasty.