AAOS Comprehensive Orthopaedic Review 4: Print + Ebook (AAOS - American Academy of Orthopaedic Surgeons)

156

Section 2 | Spine

• Several trials sponsored by the FDA have been completed with continued follow-up exceeding 20 years in the earliest patients enrolled in the trials. • The surgical approach and the method of neural decompression are essentially iden tical to that of ACDF. The artificial disk is placed into the decompressed disk space rather than bone or allograft. • Patients with focal kyphosis at the involved level, OPLL/posterior osteo phytes, diffuse idiopathic skeletal hyperos tosis, decreased disk height, or significant facet arthrosis may benefit from a fusion over a disk arthroplasty. • Advantages • Cervical disk replacement maintains motion and avoids fusion-related compli cations of nonunions and plate-and-screw complications, such as backout, esopha geal erosion, and adjacent-level ossifica tion disease. • One major long-term benefit may be the decrease in the rate of secondary surgi cal procedures when comparing one-level arthroplasty to one-level ACDF because of surgery for pseudarthrosis and decreased surgery for adjacent-level disease also seen in a study with 7 years follow-up. • Some of the differences in adjacent-level surgery rates have been attributed to some patients with artificial disks declin ing further surgery when informed that insurance and the FDA mandated that the adjacent level had to be an ACDF. Patients randomized to ACDF were not likely to refuse because their experience with ACDF was positive. • Differences in adjacent-level surgery rates are small. Meta-analyses found either no difference or differences less than 5%. • Heterotopic ossification is a finding unique to cervical disk arthroplasty and has been reported to occur at approximately 16% to 60% of treated levels although rates have been shown to decrease with use of post operative NSAIDs for heterotopic ossifica tion prophylaxis. The clinical significance of heterotopic ossification formation is still unknown.

• Preliminary results using various different prostheses have been favorable, reflecting the fact that neural decompression is the cornerstone of early clinical improvement. c. Posterolateral decompression • Posterior laminoforaminotomy can be used to decompress the nerve root without sub stantially destabilizing the spine in patients with anterolateral disk herniation or foram inal stenosis. • The compressing lesion ideally should be located so that unroofing the fora men adequately decompresses the root. Clinically, patients with decreased symptoms with neck flexion are most likely to benefit from a posterior foraminotomy. • The offending disk herniation or ante rior osteophyte can be (but does not need to be) removed as long as the com pressed span of the nerve root is released posteriorly. • Advantages • Minimal morbidity • Avoids fusion • Reported success rate of up to 91.5% • Disadvantages • Possibility for incomplete decompression in the setting of anterior compression lesions • Inability to restore disk and foraminal height at the diseased level • Because fusion is not performed, the poten tial for deterioration of results with time exists if the degenerative process continues. d. Anterior versus posterior approach • Few absolute indications exist for choosing one approach over the other for decom pressing the nerve root.

2 | Spine

• If the patient had prior surgery using one approach, it may be advantageous to per form surgery from the opposite approach to avoid working through scar tissue. For example, a posterior foraminotomy could be performed in patients with persistent radiculopathy after cervical disk arthro plasty or ACDF; however, a revision ante rior procedure can also be performed with excellent results and avoids any morbidity associated with a posterior approach. Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2023

AAOS Comprehensive Orthopaedic Review 4

© 2025 American Academy of Orthopaedic Surgeons