Porous-coated knee arthroplasty. A case report concerning bone ingrowth

The area of bone-metal interaction in uncemented implants is regarded by many investigators as the key to the success or failure of the implant. The nature of the interaction is poorly understood because the zone is technically difficult to visualize and analyze. In order to test the power of modern imaging, analyzing, and metallurgical methods in this context, a well-functioning porous-coated knee prosthesis (tibial component) removed from the knee of a 65-year-old man was sectioned and examined by light microscopy, roentgenogram, scanning electron microscopy, and radiologic energy dispersive analysis. Independently, these methods demonstrated that the prosthesis was held in situ by collagenous tissue between and below the metal pellets of the prosthesis. Calcified bone did not appear to interact with the prosthesis and is probably not a major factor for prosthesis fixation. The various analytic methods described are suitable and sufficient for further exploration on a larger scale of the zone of bone-metal contact in cementless implants.