The need for basic research concerning implantable materials was initiated when physicians first attempted to leave nonbiologic materials imbeded in the body following surgery. Nature's defense mechanism against leaving foreign material in the body has been observed since the dawn of man as exemplified by the festering of splinters, cactus barbs, and imbeded gravel. Most of these wounds were contaminated with bacteria which points toward a difference in the way the body can or will tolerate a material when sterile as opposed to the same material when not sterile.
The era of artificial organs probably had its start when early man grasped a staff to support and shift his weight from an injured limb. Modern surgical techniques now allow us to replace diseased heart valves, arteries, hip joints, etc., with artificial internal organs, I have previously defined artificial internal organs as "any artificial device designed to functionally or cosmetically replace, duplicate or augment a diseased or otherwise incompetent body part-either tem orarily or permanently-and which at some point requires that nonbiologic material interface with viable tissue" [ 11 ,
The last four words of this definition specifies the importance of the implant material-it must "interface with viable tissue." In many areas of artificial organ development, clinical evaluation is being curtailed due to a lack of suitable material which will meet both the physical and biological requirements.
Any implantable device designed to function as a body part must necessarily come into contact with viable tissue. The reaction of the tissue to the foreign material used in fabricating the device and any degradation of the material to this hostile environment becomes extremely important in the proper selection of materials. $ *As used here, the term nonbiologic tissue does not exclude reconstituted collegen, reconstituted bone, etc., but would exclude the nonviable or viable homograft or heterograft tissue and/or organs.