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Background: Implant loosening – either infectious or aseptic- is a still a major complication in the field of
orthopaedic surgery. In both cases, a pro-inflammatory peri-prosthetic environment is generated by the
immune system - either triggered by bacteria or by implant wear particles – which leads to osteoclast
differentiation and osteolysis. Since infectious cases in particular often require multiple revision surgeries, we
wondered whether commonly used surgical suture material may also activate the immune system and thus
contribute to loss of bone substance by generation of osteoclasts.
Methods: Tissue samples from patients suffering from infectious implant loosening were collected
intraoperatively and presence of osteoclasts was evaluated by histopathology and immunohistochemistry.
Further on, human monocytes were isolated from peripheral blood and stimulated with surgical suture
material. Cell supernatant samples were collected and ELISA analysis for the pro-inflammatory cytokine IL-8
was performed. These experiments were additionally carried out on ivory slices to demonstrate functionality
of osteoclasts. Whole blood samples were incubated with surgical suture material and up-regulation of
activation-associated cell surface markers CD11b and CD66b on neutrophils was evaluated by flow
cytofluorometry analysis.
Results: We were able to demonstrate that multinucleated giant cells form in direct vicinity to surgical suture
material. These cells stained positive for cathepsin K, which is a typical protease found in osteoclasts. By in vitro
analysis, we were able to show that monocytes differentiated into osteoclasts when stimulated with surgical
suture material. Resorption pits on ivory slices provided proof that the osteoclasts were functional. Release of
IL-8 into cell supernatant was increased after stimulation with suture material and was further enhanced if
minor amounts of bacterial lipoteichoic acid (LTA) were added. Neutrophils were also activated by surgical
suture material and up-regulation of CD11b and CD66b could be seen.
Conclusion: We were able to demonstrate that surgical suture material induces a pro-inflammatory response
of immune cells which leads to osteoclast differentiation, in particular in combination with bacterial infection. In
conclusion, surgical suture material -aside from bacteria and implant wear particles- is a contributing factor in
implant loosening