Characteristics of Hylamer polyethylene particles isolated from peri-prosthetic tissues of failed cemented total hip arthroplasties.

Polyethylene wear particles are one of the most important factors affecting the results of total hip arthroplasty. Hylamer, a highly crystalized ultra-high-molecular-weight polyethylene, has been used in total hip arthroplasty for wear reduction, but has exhibited high wear rate and excessive osteolysis. The aim of the present study was to examine Hylamer wear particles in peri-prosthetic tissues with osteolysis obtained from two cases of failed cemented total hip arthroplasty at 8 and 6 years after operation. Polyethylene particles were isolated, and examined using a scanning electron microscope and image analyzer. Total numbers of Hylamer polyethylene particles in the two cases were 5.6 x 10(9) and 8.0 x 10(9) g(-1). Particle sizes (in equivalent circle diameter) for the two cases were 1.07 +/- 0.06 microm and 1.16 +/- 0.05 microm, and particle shapes (roundness) were 3.05 +/- 0.22 and 3.76 +/- 0.28. The Hylamer polyethylene particles were larger in size and more elongated and their number was larger, compared with the corresponding reported values for particles generated from conventional polyethylene. This increase in particle number and elongation may lead to early osteolysis in total hip arthroplasty with Hylamer.