[The Risk of Total Joint Replacement Infectious Complications in Relation to the UHMWPE Particle Adhesion Area]

PURPOSE OF THE STUDY Periprosthetic joint infection is a major complication which in most of the cases requires a long-term administration of antibiotics and often necessitates undergoing multiple challenging surgeries. Bacterial adhesion to foreign material is one of the key risk factors associated with periprosthetic joint infection. The foreign material with large adhesion area might be also the UHMWPE (Ultrahigh molecular weight polyethylene) particles released during the wear process from the surface of articulating components. The purpose of this study is to evaluate potential adhesion areas of wear particles in relation to diverse distribution of the size and shapes of wear particles in periprosthetic tissue and to assess an increase in the risk of infectious complications associated with an increase in the adhesion area of wear particles. MATERIAL AND METHODS The size and morphology of model and real UHMWPE particles were determined with the use of light microscopy and scanning electron microscopy. By determining the morphological descriptors, the surfaces of individual particles for different distributions of polyethylene particles were calculated. When measuring the model wear particles, 6 model situations were simulated, in which comparisons with the control measurement by the BET (Brunauer-Emmet-Teller) method were made. RESULTS The variability of individual morphological descriptors demonstrates the effect on the total surface of particles. The calculated coefficient defines how many times the particle surface increases when corrected to the given descriptor (elongation, flattening, roughness, porosity). The total area of real wear particles at 1 year is 4,622 cm2, at 20 years it is 92,440 cm2. Based on our calculations, the area of particles where a biofilm is actually formed (approximately 50 bacteria may adhere to a particle of 3µm in diameter) is 809.5 cm2 at 1 year and 16,190 cm2 at 20 years. DISCUSSION According to the measurements, the size of the potential adhesion area of metal parts and polyethylene particles becomes equal already after several weeks of endoprosthesis usage and after a few years it is many times larger. The question is whether the risk of bacterial adhesion, i.e. also the risk of infectious complications of TEP actually increases. The clinical practice suggests that the number of infections e.g. 10, 15 or 20 years after the primary implantation is not statistically higher, despite the confirmed growth of potential adhesion area in the form of UHMWPE particles. This fact could be explained by a partially equal regulatory pathway of infection and polyethylene disease. The immune system stimulated by wear particles might better resist the hematogenic infection. CONCLUSIONS The study outcomes clearly indicate that the area of polyethylene wear particles considerably increases over time. In spite of the fact that only approximately 10% of wear particles show parameters (also with respect to the size of particles and bacteria) for potential bacterial adhesion, this area is many times larger than the area of metal parts of the endoprosthesis. Key words: UHMWPE particle, adhesion, biofilm, wear, TJR infection.