• Wade K Jensen, Paul A Anderson, Louis Nel, and Jeffrey P Rouleau.
• Department of Orthopedic Surgery and Rehabilitation, University of Wisconsin, Madison, WI 53792, USA.
• Spine. 2005 Nov 15; 30 (22): 2497-502.

Study DesignExplant analysis for bone ingrowth of retrieved cervical disc prosthesis in chimpanzees and humans.ObjectivesTo assess the bone ingrowth into retrieved Bryan Cervical Discs.Summary Of Background DataBone ingrowth in cervical disc prosthesis has not been documented in the literature.MethodsChimpanzee: Two chimpanzees underwent placement of the Bryan disc at C3-C4 and 3 months later had explantation and interbody fusion. Human: Two patients had removal of their Bryan disc and interbody fusion for failure to resolve symptoms at 8 and 10 months. The explants were analyzed for bone ingrowth.ResultsChimpanzee: Histologic analysis showed bony ingrowth through the interstices of the porous coating and apposition ranging from 10% to 50% of toluidine blue-stained sections. New ingrowth, rather than bony impaction, was confirmed with fluorochrome-labeled sections Human: Bone ingrowth was a mean of 30.1% (12% SD). No difference was observed between peripheral, intermediate, or central locations.ConclusionsAdequate bony apposition was found in all primate device-to-vertebral body interfaces. Human retrievals also demonstrated significant ingrowth in all four surfaces. This compares with hip and knee arthroplasty percent ingrowth rates of 10% to 30%. All implants had stable fixation judged by radiographs and at the time of implant removal.

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