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Cervical Disc Prosthesis in Humans: First Failure

Study Design. Prospective preliminary trial of a cervical disc prosthesis. Objective. To study the feasibility, efficacy in maintaining intervertebral mobility, and complications of a low-profile disc prosthesis implanted after single-level cervical discectomy. Summary of Background Data. Since studies reported by Baba et al, there is fear that degeneration of the intervertebral disc levels adjacent to cervical arthrodesis may be exacerbated by this arthrodesis. For this reason, several cervical prostheses have been designed as an alternative to arthrodesis. None of these prostheses, some of which are bulky, has been shown to be efficacious. Methods. Five women and five men (average age, 36 years) underwent implantation of the present disc prosthesis after single-level discectomy. The discectomy was performed for cervical disc herniation that resulted in cervicobrachial pain for more than 3 months. None of the patients exhibited intervertebral instability on bending films. Preoperative magnetic resonance studies showed a noncontained disc herniation in all 10 patients and osteophytes in 2 of the patients. Results. The cervicobrachial pain resolved in all 10 patients. Intense neck pain developed in 1 patient who underwent revision surgery to remove the prosthesis and perform an arthrodesis. Another patient developed neck pain but refused the proposed revision operation. Bending films showed mobility of the intervertebral space containing the prosthesis in both of these patients. In the 8 patients who remained pain free after the operation, lateral bending films at follow-up found no mobility of the implanted disc level. Five of these eight patients had circumferential fusion, 2 had posterior fusion, and 1 had anterior fusion. Conclusion. This prosthesis failed to achieve the desired effect because the intended mobility failed to persist in 8 of the 10 patients and pain developed in the other 2 patients, in whom the mobility persisted.