Cervical Disc Arthroplasty Compared with Arthrodesis for the Treatment of Myelopathy

K Daniel Riew, Jacob M Buchowski, Rick Sasso, Thomas Zdeblick, Newton H Metcalf, Paul A Anderson
2008 Journal of Bone and Joint Surgery. American volume  
FROM THE ORIGINAL ARTICLE BACKGROUND: Although there have been case reports describing the use of cervical disc arthroplasty for the treatment of myelopathy, there is a concern that motion preservation may maintain microtrauma to the spinal cord, negatively affecting the clinical results. As we are not aware of any studies on the use of arthroplasty in this scenario, we performed a cross-sectional analysis of two large, prospective, randomized multicenter trials to evaluate the efficacy of
more » ... cal disc arthroplasty for the treatment of myelopathy. METHODS: The patients in the current study were a cohort of patients who were enrolled in the United States Food and Drug Administration Investigational Device Exemption studies of the Prestige ST and Bryan disc replacements (Medtronic, Memphis, Tennessee). The inclusion criteria were myelopathy and spondylosis or disc herniation at a single level from C3 to C7. Clinical outcome measures were collected preoperatively and at six weeks, three months, six months, twelve months, and twenty-four months postoperatively. INDICATIONS 1, 6, [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] : Radiculopathy attributable to cervical disc degeneration at one, two, or three levels or myelopathy due to cervical disc degeneration and minimal spondylotic changes at one, two, or three levels with retrodiscal spinal cord compression Radiographic evidence of cervical disc herniation or spondylosis at one, two, or three levels Symptoms corresponding to anatomical findings between C3 and C7 Failure of nonoperative treatment (after a minimum of six weeks, but most commonly after three months) continued CRITICAL CONCEPTS Structural instability of the cervical spine, acute fracture, rheumatoid arthritis with instability, or previous cervical laminectomy, which could lead to instability after the procedure Severe spondylosis with complete loss of disc height or motion of <2°, ankylosing spondylitis, or diffuse idiopathic skeletal hyperostosis, which could limit the amount of motion following the procedure Congenital stenosis, ossification of the posterior longitudinal ligament, or myelopathy due to any other etiology that causes retrovertebral compression Axial neck pain as the solitary symptom (because axial neck pain, which is often due to facet arthropathy and/or disc degeneration, does not predictably resolve following cervical disc arthroplasty) A history of recent cervical spine infection Osteoporosis and related metabolic bone diseases, which may preclude osseous growth into the arthroplasty device, leading to its loosening Morbid obesity that precludes an anterior cervical approach Inability to visualize the treated segment radiographically during surgery PITFALLS: Neutral positioning of the neck during the procedure is critical. If the neck is hyperextended, an excessive amount of the posterior end plate may be removed to produce parallel surfaces during end plate preparation, resulting in a prosthesis that rests in a kyphotic position. If the neck is placed in a kyphotic position, too much of the anterior end plate is removed and the prosthesis may rest in a lordotic position. Successful disc space preparation requires only light decortication of both end plates, removal of all posterior vertebral osteophytes, and thorough foraminal decompression. Accurate identification of the midline is required. Furthermore, midline placement of distraction pins that are used during the decompression is critical in order to avoid asymmetric distraction across the disc space, with resultant asymmetric decompression and end plate preparation, the potential development of uneven loads across the segment, and, in severe cases, a scoliotic deformity. End plate preparation must be performed carefully and judiciously in order to minimize excessive end plate resection because the majority of the end plate should be preserved to support the stresses associated with motion across the disc space and to prevent end plate subsidence. Furthermore, the various arthroplasty systems have different requirements for end plate removal, with which the surgeon should be familiar. A wider and more thorough uncinate process and osteophyte resection is necessary when a cervical disc replacement is performed in patients with myelopathy (and even in patients with spondylotic radiculopathy) than is the case when a fusion is performed in such patients. If the decompression is inadequate, continued motion across the segment may lead to recurrence of symptomatic spondylosis; in contrast, after cervical fusion procedures, osteophytes often regress once a solid fusion has been obtained. Sizing should be critically assessed to allow as large an end plate footprint as possible. Overdistraction should be avoided. AUTHOR UPDATE: Cervical disc arthroplasty continues to be a successful procedure for the treatment of myelopathy when spinal cord compression is localized to the disc space (i.e., when compression is retrodiscal in nature) and mild spondylotic changes (or no such changes) are present. For these reasons, in general, the procedure is most successful for patients younger than those with cervical spondylotic myelopathy (who frequently present with substantial degenerative changes such as facet arthropathy, which is a contraindication to cervical disc arthroplasty).
doi:10.2106/jbjs.g.01608 pmid:18978404 fatcat:vvjpb5ng5ff7zki3tsuco3jzpy