Morphology and Localisation of Patient Hip Replacement-Derived Debris and Hip Prostheses Materials in Macrophages
Whilst total hip replacement and hip resurfacing arthroplasties have been largely successful to relieve pain and restore mobility for patients, aseptic loosening is still the most common cause for revision surgery. It is thought there is a contribution from both the sensitivity to the debris produced by implant wear as well as the macrophage-mediated response, producing pro-inflammatory cytokines and increasing the risk of an adverse reaction, including osteolysis. Macrophages respond to the presence of wear debris and degrade the materials via phagocytosis, resulting in the production of toxic ions capable of migrating to other areas of the body. Both characterisation and localisation of wear debris from different implants were investigated as the level of reaction between patients varies and it is hypothesised that the size, shape and material contribute to the level of reaction. Macrophage response to implant material types found in patient samples was also explored, comparing material uptake and early phagocytosis. Using electron, confocal and light microscopy, results were gathered in the form of images for interpretation. Results confirmed macrophages responded to the presence of particles and inflammation varied with or without the presence of particles, characterised by numerous lymphocytes. Particle characterisation agreed with previous research, with both micron-sized and nano particles present. Elemental analysis revealed cobalt, chromium and titanium particles in patient tissues and patient-derived loose particles. Commercial particle uptake was confirmed for these materials in vitro, localising to phagosomes or in the cytoplasm, sometimes in gross quantities. Titanium formed needle-shaped particles which increased apoptosis and altered macrophage appearance. Surface characteristics varied for patient particles, further concluding the formation of aggregates. The findings suggest retention of large, irregular aggregates and cobalt ions from large quantities of readily phagocytosed nano particles promote inflammation. Future work would include assessing oxidative damage and cytokine production in repeated conditions.
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