Isolation and characterization of wear debris generated in patients wearing polyethylene Hylamer insert gamma irradiated in air.

Hylamer polyethylene was used in the early 1990’s to make hip joint components. Clinical experience has shown that these components, if sterilized by gamma rays in the presence of oxygen, are easily affected by wear, which leads to osteolysis. The authors analyzed polyethylene wear particles in seven patients who had received Hylamer polyethylene implants sterilized by gamma rays in air and had suffered prosthetic loosening. The results were compared to those of six controls who had received conventional polyethylene implants sterilized by the same method. The frequency distribution of globular and fibrillar particles was similar in both groups (38.5 % in Hylamer, 45.2 % in controls). The globular particles in the Hylamer samples had a mean area of 0.12 micron2, which was significantly less than that of controls (0.30 micron2). The thickness of fibrillar particles in the Hylamer samples was significantly lower than that of controls. Therefore, the two materials, despite undergoing the same type of sterilization, produced different types of wear, connected to their different properties. In conclusion, the difference in amount and morphology of Hylamer polyethylene wear particles in comparison with PCA might have caused a more intensive biological response, early and massive osteolysis, and therefore, early loosening.