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In orthopedic trauma surgery, traditional socket-based prostheses are associated with functionally limiting problems affecting 1.7 million amputees in the United States. To improve post-surgical performance and minimize socket-related complications, bone-anchored (osseointegrated) prostheses have been developed. Functionally superior, their widespread implementation has been limited due to infection. In an unacceptable number of patients well-organized biofilm ecosystems of bacteria colonize the osseointegrated implant (OI) and migrate into device-tissue interface, leading to superficial and deep infections, and implant failure. Since the OI implant protrudes through the skin, the site is easily contaminated by microbes. The problem is worsened by increased resistance to antibiotics contributing significantly to surgical outcome failure. Antimicrobial photodynamic therapy (aPDT)—which uses photosensitizers excited with visible light to disrupt biofilms and kill bacteria with produced reactive oxygen species—has been proposed to address this problem. To assess biofilm formation and aPDT effectiveness, we describe a rabbit OI model and steps to investigate the ability of aPDT using 5-Aminolevulinic acid (5-ALA)-based light therapy to control methicillin-resistant S. aureus (MRSA) bacterial infection. As part of an institutionally approved survival surgery, this model involves lower limb amputation at the tibia, OI installation and MRSA inoculation. Within a week of biofilm formation, the optimal aPDT regime of light and 5-ALA dose was applied to the implant-skin interface to eradicate migrating biofilms. We have built a circumferential light source spectrally shaped for optimal photoactivation and cooled without risk of bacteria dispersal. Optical coherence tomography (skin flap healing and side-effects), micro-computed tomography (OI-bone integrity) and bioluminescence (bacterial bioburden before and after aPDT) imaging were used to monitor outcome for up to three weeks post-treatment.
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