Abstract
Recently, highly cross-linked polyethylene has been highlighted in THAs which is thought to reduce wear. However, little is known about an accurate nature of cross-linked polyethylene particles and long term wear in vivo. One of the authors implanted all polyethylene cups irradiated by 100 Mrad in 1970s. Recently, we performed two revisions with this cup. In the present study, we extracted polyethylene particles and made direct wear measurements on retrieved cups.
Case one was revised for a stem fracture and acetabular loosening at 25 years postoperatively and case two for acetabular loosening at 27 years postoperatively. There was no osteolysis on X rays. We extracted polyethylene particles using a tiussue digestion and image analysis developed by Cambell and measured wear of retrieved cups using casting and 3D scanner developed by us.
Equivalent circle diameter (ECD) was 0.73 um, roundness was 0.69, aspect ratio (AR) was 1.4 and number of particles was 6.0 hundreds million/g wet tissue in case one. ECD was 0.57 um, roundness was 0.62, AR was 1.54 and number of particles was 5.8 hundreds million/g in case two. SEM showed that granule or globular shapes were abundant and fibril shapes were rare. Direct wear measurement showed concentric wear patterns were observed with very low linear wear (less than 0.03 mm).
Cross-linked polyethylene particles were less, a little smaller and much rounder in compared with our previous result of conventional polyethylene in peri-implant tissue. No unidirectional and significant amount of wear was observed in retrieved cups even after over 25 years.
The abstracts were prepared by Nico Verdoschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, Universitair Medisch Centrum, Orthopaedie / CSS1, Huispost 800, Postbus 9101, 6500 HB Nijmegen, Th. Craanenlaan 7, 6525 GH Nijmegen, The Netherlands.
