Polyurethane polymer is a closed-cell lacunar system not permeable to water-soluble dyes, to carbon dioxide under twenty pounds of pressure, or to the rapid ingrowth of living tissue.
New-boune formation does not often occur immediately adjacent to the polyurethane in rabbits within twelve weeks of implantation. In the sections where such bone formation was observed it did not comprise so much as 1 per cent of a low-power microscopic field.
The typical response to polyurethane is a fibrous-tissue reaction, often inflammatory in nature. New-bone formation is generally external to this zone.
Polyurethane softens within the body and usually requires metallic reinforcement if it is to remain effective.
Polyurethane should not be used where bone infection already exists.
The heat of chemical reaction of polyurethane fast-mixed at 120 degrees Fahrenheit rises to such a degree that it coagulates protein.