Rick C. Sasso and Ben J. Garrido

Description

Anterior cervical diskectomy and fusion has historically been the gold standard treatment for patients experiencing cervical radiculopathy or myelopathy refractory to nonoperative measures. The safety and effectiveness of this procedure have been established and demonstrated in the literature; however, limitations have evolved, and subsequently alternatives such as disk replacement are being investigated. Such innovative technology has addressed kinematic and biomechanical factors in cervical spine motion. Intervertebral disk replacement is designed to preserve motion, both at the affected and adjacent levels, and avoid limitations of fusion. Hilibrand et al have described adjacent level degeneration in patients having undergone cervical fusion at a rate of 2.9% of patients per annum. Such new-onset degenerative changes and possible recurring neurologic symptoms may be deferred or eliminated with cervical disk replacement. In addition, potential complications related to fusion such as pseudarthrosis, anterior plate problems, and morbidity associated with bone graft harvest may be avoided. Cervical disk arthroplasty is designed to provide physiologic motion and eliminate abnormal loading stresses at adjacent levels that lead to accelerated degeneration.

Expectations

Disk arthroplasty results may be highly subject to procedural technique. Preoperative planning with magnetic resonance imaging (MRI) or computed tomography (CT) myelogram is essential to determine neural compressive lesions. Appropriate disk sizing and assessment of excessive osteophytes is performed with preoperative CT scans. Disk height should be relatively normal without profound collapse, facet joints must not be extremely degenerated, and reasonably normal motion must be present. Intraoperative patient positioning is supine, with the spine stabilized in neutral position without hyperextension. It is important to perform adequate decompression of both the spinal canal and the bilateral neuroforamen. With motion-sparing techniques, it is extremely important to adequately decompress the asymptomatic side as well as the target site. Appropriate end-plate preparation is critical to allow for bony ingrowth into the prosthetic shell while maintaining the strong subchondral end plate. Undersizing the base-plate area may result in end-plate damage and implant subsidence. Prosthetic disk placement is confirmed under fluoroscopy. Postoperative immobilization is not required.

Indications

Intervertebral disk replacement is indicated for cervical radiculopathy due to a herniated disk or osteophyte complex at a single level between C3 and C7. These patients must have failed aggressive nonoperative treatment modalities and be skeletally mature with relatively normal segmental motion.

Contraindications

Cervical disk replacement surgery should not be performed in patients with sagittal plane abnormalities, spondylolisthesis, retrolisthesis, spondylolysis, or any evidence of segmental instability. Poor surgical candidates and those with active systemic or operative site infection should be excluded. Those patients who have a history of previous cervical surgery, metabolic bone disease, progressive neuromuscular disease, or significant osteoporosis, or are on corticosteroid therapy, should not be considered for this procedure. In addition, radiographically confirmed ankylosis, ossification of the posterior longitudinal ligament (OPLL), fixed kyphosis, and incompetent end-plate or severe facet joint arthritic changes should also be excluded. Cervical myelopathy secondary to factors other than a soft disk herniation at the level to be treated via an anterior diskectomy decompression should be avoided.

Special Considerations