Key Concepts of Musculoskeletal Infection.

Over the past few decades, musculoskeletal infections have increased in both incidence and severity. The clinical manifestations of musculoskeletal infections range from isolated osteomyelitis to multisite infections with systemic complications. Although this increased incidence of musculoskeletal infections correlates with the increased incidence of methicillin-resistant Staphylococcus aureus infections, other nonresistant infectious organisms have been associated with severe musculoskeletal infections; this finding supports the likelihood that an antibiotic resistance profile is not a major factor in bacterial virulence. Instead, a multitude of virulence factors allow infectious organisms to manipulate and evade the immune response of the host. Organisms such as S aureus and Streptococcus pyogenes are able to hijack the acute phase response of the host, which allows for protected proliferation and dissemination. The serum factors produced by the acute phase response, including interleukin-6, C-reactive protein, erythrocytes/fibrinogen, and platelets, can be used to assess musculoskeletal infection severity and monitor treatment. Bacterial genome sequencing has identified virulence factors in a wide variety of clinical manifestations of musculoskeletal infections and may help identify targets for clinical therapy. Currently, however, the management of musculoskeletal infections relies on accurate organism identification and a thorough recognition of the sites of infection and the tissues that are involved. MRI aids in the localization of musculoskeletal infection and identification of sites that require surgical débridement.