The Bryan Cervical Disc: wear properties and early clinical results.

BACKGROUND CONTEXT The rationale for motion preservation by disc replacement after anterior cervical discectomy is to diminish long-term morbidity secondary to adjacent segment degeneration. However, these disc prostheses will be subject to wear and its possible adverse consequences. PURPOSE Assess the in vitro and in vivo wear properties of the Bryan Cervical Disc and the early clinical results. STUDY DESIGN In vitro mechanical testing, caprine animal model and prospective European human trial. OUTCOME MEASURE In vitro mechanical testing used American Society for Testing and Materials standards to measure wear rates and debris. Caprine results were analyzed by histopathologic analysis by a blinded veterinary pathologist. Clinical outcomes were measured by Odoms's criteria, independent radiologic analysis and Short Form-36. METHODS In vitro wear testing in cervical spine simulator for up to 40 M cycles. Wear rates were determined and particles analyzed microscopically. The in vivo inflammatory response was studied in goats that had discectomy at C4-C5. They were sacrificed between 3 and 12 months and histopathologically were compared with controls who had fusions with titanium plates. A prospective clinical trial of 136 patients with minimum 1-year follow-up was analyzed using validated questionnaires and radiographs. RESULTS In vitro wear averaged approximately 1.76% by weight at 10 M cycles and 18% at 40 M cycles. Wear debris were present in the periprosthetic tissues in 4 of 11 animals without inflammatory response. The early clinical results were satisfactory in over 90% of patients. CONCLUSION The in vivo and in vitro wear properties are satisfactory for the expected duration of life of the prosthesis. The early clinical results are satisfactory and equal to fusion.