IntroductionThe influence of polyacetal wear particles on aseptic loosening of non-cemented isoelastic femoral stems with polyacetal coating remains unclear. The aim of our study was to use nuclear methods to prove the presence of polyacetal wear particles, to determine their morphology and to check their distribution in the tissues around loosend hip prosthetic components.MethodsTissue samples obtained during retrieval of 4 aseptic loosened primary hip prostheses with isoelastic stems made of polyacetal were subjected to nuclear analyses. Proton microbrobe method (mikro-PIXE) was used to prove the presence of polyacetal wear particles and to check for their morphology by detection of barium, which is molecularly in BaSO4 embedded in polyacetal. Thermal neutron activation was used to determine distribution pattern of polyacetal wear in the peri-prosthetic tissues.ResultsAgainst expectations, polyacetal wear particles were found rather rare, larger than 100 µm and present in pseudo-membrane samples around the loosened stem, but virtually absent in tissues away from their origin. Concentration of BaSO4 in polyacetal wear particles in pseudo-membrane samples was similar to the one in polyacetal coating (conc. Ba = 14217 µg/g and 14800 µg/g, respectively).ConclusionAccording to the results, the primary cause of the loosening of the isoelastic stems with polyacetal coating is most probably mechanical restlessness, which is responsible for local production of the large polyacetal wear particles responsible to accelerate the process of loosening. PIXE method and thermal neutron activation are sensitive quantitative nuclear methods suitable for direct or indirect detection of wear particles in the tissue around loosened prostheses and to determine morphology of wear particles and their distribution in the tissues.
Analiza tkiva okrog omajanih umetnih kolčnih debel iz poliacetala z uporabo nuklearnih metod