Microbes and Bone Health – Friends or Foes?

Pathogenic microbes have historically been associated with poor health outcomes in orthopaedic surgery, however, recent findings have suggested that commensal gut microbes may be beneficial in promoting bone health. Novel biomaterial strategies to combat pathogenic microbes in periprosthetic joint infection will first be presented. To locally treat orthopaedic infections, antibiotics are often directly incorporated into poly(methyl methacrylate) (PMMA) bone cement. This strategy, however, results in insufficient elution of drug for treatment of chronic infections and few antibiotics are compatible. To address these limitations, a composite PMMA-based material containing polymerized cyclodextrin (CD) microparticles was developed. PMMA-CD composites were compatible with a broader range of antibiotics, able to treat chronic broad-spectrum infections, and had the capacity to be refilled with drugs after implantation to provide additional windows of therapy. Next, associations between the composition of the gut microbiome and bone health in clinical and in vivo studies will be discussed. A prospective pilot study investigating the composition of the gut microbiome of spinal fusion surgery patients demonstrated that the microbiome differed among spinal fusion patients based on their bone mineral density. Finally, the relationship between microbiome composition, bone acquisition, and bone tissue strength was studied using an in vivo model. Male and female C57Bl/6 mice had their gut microbiota altered using oral antibiotics for different periods of time until six months of age. Findings suggested that the gut microbiome can influence bone tissue strength after skeletal maturity and that it may be possible to improve bone matrix later in life through the microbiome.