Analysis of polyethylene particles isolated from periprosthetic tissue of loosened hip arthroplasty and comparison with radiographic appearance.

Aseptic loosening is the major problem associated with joint arthroplasty, but little is known about the precise mechanism of osteolysis. To elucidate this mechanism we analyzed polyethylene particles retrieved from granulation tissue around the stem of loosened hip arthroplasties. Granulation tissue was obtained from 35 patients at revision surgery for a loosened hip and digested with papain, followed by ultracentrifugation. The isolated particles were identified with ultra-high molecular weight polyethylene particles by Fourier transform infrared spectroscopy. The morphology and number of particles were analyzed by scanning electron microscopy. Most of the particles were granular, with 87.9% being less than 1 microm in equivalent circle diameter (mean 0.83 +/- 0.45 microm). The mean number of particles per gram of tissue was 1.48 x 10(9) (range 7.59 x 10(7) to 1.15 x 10(10)). We compared these data to the radiological appearance and found that focal-type osteolysis contained more particles than the linear type. The amount of submicron-sized particles is related to the development of osteolysis.