A radiostereometric analysis of the Bryan® cervical disc prosthesis

Study Design. Prospective, radiostereometric study of the Bryan (R) Cervical Disc prosthesis (Medtronic Sofamor Danek, Memphis, TN) for the treatment of a single-level disc disease of the cervical spine. Objective. To study the stability of the titanium end-plates of the disc prosthesis at the interface between the bone and prosthesis. Summary of Background Data. Cervical disc prosthesis is a motion-sparing technology in which the longevity is dependent on initial fixation as well as secondary fixation with bone ingrowth into the surface of the device. Little is known regarding the stability of this fixation with the currently studied prosthesis. Methods. Eleven patients with symptomatic cervical radiculopathy underwent implantation of a radiostereometry modified Bryan (R) prosthesis after a standard anterior cervical discectomy. The adjacent vertebrae were perioperatively marked with tantalum markers. The patients were then frequently studied with radiostereometric radiographs and evaluated for pain, and neurologic and physical function for 2 years. Results. Both titanium endplates of the device were immediately stable in 5 patients. Small but measurable changes (micromotions) were recorded in 4 patients until the 3-month examination and in 2 patients at the 3-6-month time period. All prostheses continued to be stable after 6 months until the final assessment at 2 years after surgery. The recorded micromotions did not influence the clinical results. Conclusions. The Bryan (R) prosthesis is immediately stable in many patients and is securely fixed to the bone within 3-6 months in all patients. The result of this study suggests that there is sufficient bone ingrowth on the coated surface of the Bryan (R) prosthesis endplates to stabilize securely the prosthesis.