In the Prestige ST trial, at twenty-four months after surgery, 47.9% (95% confidence interval, 33.3% to 62.8%) of the patients in the arthroplasty group (twenty-three of forty-eight patients) and 37.8% (95% confidence interval, 22.5% to 55.2%) of those in the arthrodesis group (fourteen of thirty-seven patients) had improvement in gait function, no patient in either group had deterioration in gait function, and 52.1% (95% confidence interval, 37.2% to 66.7%) of the patients in the arthroplasty group (twenty-five of forty-eight patients) and 62.2% (95% confidence interval, 44.8% to 77.5%) of the patients in the arthrodesis group (twenty-three of thirty-seven patients) had maintenance of gait function. In the Bryan study, at twenty-four months after surgery, 46.2% (95% confidence interval, 30.1% to 62.8%) of the patients in the arthroplasty group (eighteen of thirty-nine patients) and 26.7% (95% confidence interval, 12.3% to 45.9%) of those in the arthrodesis group (eight of thirty patients) had improvement in gait function. No patient in either group had deterioration of gait function, and 53.8% (95% confidence interval, 37.2% to 69.9%) of the patients in the arthroplasty group (twenty-one of thirty-nine patients) and 73.3% (95% confidence interval, 54.1% to 87.7%) of those in the arthrodesis group (twenty-two of thirty patients) had maintenance of gait function. At twenty-four months, there were no significant differences in neurological function or in improvement in gait function between the arthroplasty and arthrodesis groups in either study.
The current approved indication in the United States for cervical disc arthroplasty is the treatment of radiculopathy and/or myelopathy due to neural compression caused by a disc herniation or spondylotic changes (that is, retrodiscal compression). Although early data from several different Investigational Device Exemption studies have suggested that arthroplasty appears to be a promising alternative to arthrodesis for the treatment of cervical spondylotic disease1,4,9,12,13,15,31, aside from case reports and small case series, we are not aware of any studies that have been performed to evaluate the role of cervical disc arthroplasty in the treatment of myelopathy caused by retrodiscal compression. There is concern that preserving motion in patients with myelopathy may theoretically maintain microtrauma to the compromised cord, resulting in adverse long-term results. Also, the preservation of motion may prevent osteophyte remodeling, which can occur in association with a fusion in turn leading to a decrease in residual compression once a fusion occurs. Furthermore, cervical disc arthroplasty, by maintaining motion, may be associated with late osteophyte formation1,3,32. Finally, there is concern that, in patients with kyphotic alignment or in those in whom the arthroplasty device is placed in a kyphotic alignment, progressive kyphosis may develop, leading to recurrence or worsening of myelopathic symptoms25.
Fortunately, despite these theoretical concerns, the current study showed clinical improvement in patients with disc-based spinal cord compression due to disc herniation and/or spondylotic disease. We found that all functional outcome measures studied were similar between the arthroplasty and arthrodesis groups. More importantly, however, we noted similar improvement in neurological status and gait function in the arthroplasty and arthrodesis groups, and not a single patient in the arthroplasty group had deterioration in neurological function during the study period. This finding suggests that, at least at two years postoperatively, with a thorough decompression, arthroplasty appears to be similar to arthrodesis for the treatment of cervical myelopathy due to retrodiscal compression at a single level secondary to a disc herniation and/or spondylotic changes localized to the disc space. It must be emphasized, however, that the present study did not address the use of cervical disc arthroplasty for the treatment of myelopathy due to neural compression behind the vertebral body (that is, retrovertebral compression), such as from ossification of the posterior longitudinal ligament, as the abnormality in the present study was limited to the disc space. Additionally, patients with small spinal canals and multilevel disease were not assessed in the present study. Last, as the present study was a secondary, exploratory, unplanned pooled analysis, the results should be regarded as hypothesis-generating and not as conclusive and should not be interpreted to mean that cervical disc arthroplasty is superior to arthrodesis.
The majority of the literature on cervical arthroplasty has been focused on the outcomes of the procedure in a mixed cohort of patients with both radiculopathy and myelopathy7,20-22,24,33. Although several studies have been published on the use of cervical arthroplasty for the treatment of myelopathy25-27, those studies have been limited by a small number of patients and short follow-up. For example, Sekhon reported on a series of eleven patients who presented with cervical myelopathy resulting from anterior spinal cord compression secondary to spondylotic stenosis or acute disc herniation who were managed with Bryan disc replacement26. Although only five patients were followed for eighteen months or more, all patients had radiographic documentation of a decompressed spinal cord and, on the average, improvements of one Nurick grade and of 45% on the Neck Disability Index were observed postoperatively. The other studies demonstrated similar results25,27. Our results further validate those preliminary findings that arthroplasty appears to work reasonably well in the short term for the treatment of myelopathy due to retrodiscal compression.
One limitation of the present study is the relatively short duration of follow-up. A minimum of five to ten years of follow-up has been recommended for such procedures6,7. There are general concerns related to the use of disc arthroplasty with regard to material wear31,34-36 and the ability of these disc prostheses to maintain motion37-39. Another concern is whether disc arthroplasty may lead to the recurrence of syndesmophytes. There is a concern that motion preserved by cervical disc arthroplasty may lead to recurrence of these osteophytes after the initial decompression1,3,32. Finally, there is concern that in patients with kyphotic alignment or in those in whom the arthroplasty device is placed in a kyphotic alignment, progressive kyphosis may occur following cervical disc arthroplasty, leading to recurrence or worsening of myelopathic symptoms as occurred in one patient in the study by Sekhon26. These questions cannot be answered without long-term follow-up and a specifically designed study to address such issues. Last, we were not able to critically evaluate radiographic features that may have affected the outcome in myelopathic patients such as canal size or whether the cord compression was caused by a disc herniation or spondylosis.
In conclusion, spinal motion maintained by cervical disc arthroplasty does not appear to have an adverse effect in the setting of myelopathy due to retrodiscal compression at up to two years after arthroplasty. It must be emphasized, however, that the present study does not address the use of cervical disc arthroplasty in the setting of retrovertebral compression, and, therefore, we believe that patients with myelopathy due to cord compression behind the vertebral body should not undergo cervical disc arthroplasty. In addition, although short-term results of cervical disc arthroplasty appear encouraging, studies with at least five to ten years of follow-up are required before cervical disc replacement can be viewed as a standard treatment of disc-based cervical myelopathy.
A table summarizing Nurick grade changes is available with the electronic versions of this article, on our web site at jbjs.org (go to the article citation and click on “Supplementary Material”) and on our quarterly CD/DVD (call our subscription department, at 781-449-9780, to order the CD or DVD).
Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from Medtronic. In addition, one or more of the authors or a member of his or her immediate family received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (Medtronic). Also, commercial entities (Medtronic) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 to a research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which one or more of the authors, or a member of his or her immediate family, is affiliated or associated.
A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM/DVD (call our subscription department, at 781-449-9780, to order the CD-ROM or DVD).
Investigation performed at Washington University in St. Louis, St. Louis, Missouri; Indiana Spine Group, Indianapolis, Indiana; and University of Wisconsin, Madison, Wisconsin
1. Albert TJ, Eichenbaum MD. Goals of cervical disc replacement. Spine J. 2004;4(6 Suppl):292S-293S.
2. Anderson PA, Rouleau JP. Intervertebral disc arthroplasty. Spine. 2004;29:2779-86.
3. Anderson PA, Sasso RC, Riew KD. Update on cervical artificial disk replacement. Instr Course Lect. 2007;56:237-45.
4. Bertagnoli R, Duggal N, Pickett GE, Wigfield CC, Gill SS, Karg A, Voigt S. Cervical total disc replacement, part two: clinical results. Orthop Clin North Am. 2005;36:355-62.
5. Bertagnoli R, Yue JJ, Pfeiffer F, Fenk-Mayer A, Lawrence JP, Kershaw T, Nanieva R. Early results after ProDisc-C cervical disc replacement. J Neurosurg Spine. 2005;2:403-10.
6. Bryan VE Jr. Cervical motion segment replacement. Eur Spine J. 2002;11:S92-7.
7. Goffin J, Van Calenbergh F, van Loon J, Casey A, Kehr P, Liebig K, Lind B, Logroscino C, Sgrambiglia R, Pointillart V. Intermediate follow-up after treatment of degenerative disc disease with the Bryan Cervical Disc Prosthesis: single-level and bi-level. Spine. 2003;28:2673-8.
8. Lafuente J, Casey AT, Petzold A, Brew S. The Bryan cervical disc prosthesis as an alternative to arthrodesis in the treatment of cervical spondylosis: 46 consecutive cases. J Bone Joint Surg Br. 2005;87:508-12.
9. Link HD, McAfee PC, Pimenta L. Choosing a cervical disc replacement. Spine J. 2004;4 (6 Suppl):294S-302S.
10. McAfee PC. The indications for lumbar and cervical disc replacement. Spine J. 2004;4 (6 Suppl):177S-181S.
11. Mummaneni PV, Haid RW. The future in the care of the cervical spine: interbody fusion and arthroplasty. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004. J Neurosurg Spine. 2004;1:155-9.
12. Phillips FM, Garfin SR. Cervical disc replacement. Spine. 2005;30(17 Suppl):S27-33.
13. Pickett GE, Sekhon LH, Sears WR, Duggal N. Complications with cervical arthroplasty. J Neurosurg Spine. 2006;4:98-105.
14. Pimenta L, McAfee PC, Cappuccino A, Bellera FP, Link HD. Clinical experience with the new artificial cervical PCM (Cervitech) disc. Spine J. 2004;4(6 Suppl):315S-321S.
15. Pracyk JB, Traynelis VC. Treatment of the painful motion segment: cervical arthroplasty. Spine. 2005;30(16 Suppl):S23-32.
16. Singh K, Vaccaro AR, Albert TJ. Assessing the potential impact of total disc arthroplasty on surgeon practice pattern in North America. Spine J. 2004;4(6 Suppl):195S-201S.
17. Traynelis VC. Spinal arthroplasty. Neurosurg Focus. 2002;13:E10.
18. Wigfield CC, Gill SS, Nelson RJ, Metcalf NH, Robertson JT. The new Frenchay artificial cervical joint: results from a two-year pilot study. Spine. 2002;27:2446-52.
19. Yoon DH, Yi S, Shin HC, Kim KN, Kim SH. Clinical and radiological results following cervical arthroplasty. Acta Neurochir (Wien). 2006;148:943-50.
20. Coric D, Finger F, Boltes P. Prospective randomized controlled study of the Bryan Cervical Disc: early clinical results from a single investigational site. J Neurosurg Spine. 2006;4:31-5.
21. Hacker RJ. Cervical disc arthroplasty: a controlled randomized prospective study with intermediate follow-up results. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2005. J Neurosurg Spine. 2005;3:424-8. Erratum in: J Neurosurg Spine. 2006;4:189.
22. Porchet F, Metcalf NH. Clinical outcomes with the Prestige II cervical disc: preliminary results from a prospective randomized clinical trial. Neurosurg Focus. 2004;17:E6.
23. Robertson JT, Papadopoulos SM, Traynelis VC. Assessment of adjacent-segment disease in patients treated with cervical fusion or arthroplasty: a prospective 2-year study. J Neurosurg Spine. 2005;3:417-23.
24. Sasso R, Rouleau J. Cervical kinematics in ACDF and disc replaced subjects. Spine J. 2005;5:87S.
25. Sekhon LH. Cervical arthroplasty in the management of spondylotic myelopathy. Spine Disord Tech. 2003;16:307-13.
26. Sekhon LH. Cervical arthroplasty in the management of spondylotic myelopathy: 18-month results. Neurosurg Focus. 2004;17:E8.
27. Sekhon LH. Two-level artificial disc placement for spondylotic cervical myelopathy. J Clin Neurosci. 2004;11:412-5.
28. The natural history and the results of surgical treatment of the spinal cord disorders associated with cervical spondylosis. Brain. 1972;95:101-8.
29. Vernon H, Mior S. The Neck Disability Index: a study of reliability and validity. J Manipulative Physiol Ther. 1991;14:409-15. Erratum in: J Manipulative Physiol Ther. 1992;15(1).
30. Ware JE Jr, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care. 1992;30:473-83.
31. Anderson PA, Sasso RC, Rouleau JP, Carlson CS, Goffin J. The Bryan Cervical Disc: wear properties and early clinical results. Spine J. 2004;4:303S-309S.
32. Goffin J, Van Loon J, Van Calenbergh F. Cervical arthroplasty with the Bryan disc: 4-year results. Read at the 21st Annual Meeting of the North American Spine Society; 2006 Sept. 26-30; Seattle, WA.
33. Robertson JT, Metcalf NH. Long-term outcome after implantation of the Prestige I disc in an end-stage indication: 4-year results from a pilot study. Neurosurg Focus. 2004;17:E10.
34. Anderson PA, Rouleau JP, Toth JM, Riew KD. A comparison of simulator-tested and -retrieved cervical disc prostheses. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004. J Neurosurg Spine. 2004;1:202-10.
35. Anderson PA, Sasso R, Riew KD, Metcalf NH. Reoperation rates of cervical arthroplasty versus arthrodesis. Spine J. 2005;5:76S-7S.
36. Chang BS, Brown PR, Sieber A, Valdevit A, Tateno K, Kostuik JP. Evaluation of the biological response of wear debris. Spine J. 2004;4(6 Suppl):239S-244S.
37. Bryan VE Jr. Cervical motion segment replacement. Eur Spine J. 2002;11:S92-7.
38. Leung C, Casey AT, Goffin J, Kehr P, Liebig K, Lind B, Logroscino C, Pointillart V. Clinical significance of heterotopic ossification in cervical disc replacement: a prospective multicenter clinical trial. Neurosurg. 2005;57:759-63.
Copyright 2008 by The Journal of Bone and Joint Surgery, Incorporated
39. Parkinson JF, Sekhon LH. Cervical arthroplasty complicated by delayed spontaneous fusion. Case report. J Neurosurg Spine. 2005;2:377-80.