Traumatic loading of the Bryan cervical disc prosthesis: An in vitro study

OBJECTIVE: The Bryan disc prosthesis (Medtronic Sofamor Danek, Memphis, TN) relies on a precise fit between the device and the vertebral endplates to provide immediate stability after cervical arthroplasty. The safety of the cervical arthroplasty in the setting of trauma is unknown. We compare the segmental strength of the normal cervical spine and the cervical spine after single-level arthroplasty. METHODS: Fifteen cadaveric cervical spines with arthroplasty placed at the C5-C6 level were compared with 16 intact cadaveric controls. A pure moment was applied to induce flexion, extension, or axial rotation until the segment failed. RESULTS: The prosthesis provided 63, 45, and 69% of the strength of a normal spine during flexion, extension, and rotation, respectively. There were no cases of prosthesis expulsion. CONCLUSION: After insertion of the Bryan disc, the remaining ligamentous tissues provide adequate acute stability to the spine.