What is Osteomyelitis?
Osteomyelitis (OM) is an infection of bone. Symptoms may include pain in a specific bone with overlying redness, fever, and weakness. The long bones of the arms and legs are most commonly involved in children, while the feet, spine, and hips are most commonly involved in adults.
In general, microorganisms may infect bone through one or more of three basic methods:
- Via the bloodstream (haematogeneously) – most common
- From nearby areas of infection (as in cellulitis)
- Penetrating trauma, including iatrogenic causes such as joint replacements or internal fixation of fractures
The area usually affected when the infection is contracted through the bloodstream is the metaphysis of the bone. Once the bone is infected, leukocytes enter the infected area, and, in their attempt to engulf the infectious organisms, release enzymes that lyse the bone. Pus spreads into the bone’s blood vessels, impairing their flow, and areas of devitalized infected bone, known as sequestra, form the basis of a chronic infection.
Often, the body will try to create new bone around the area of necrosis. The resulting new bone is often called an involucrum. On histologic examination, these areas of necrotic bone are the basis for distinguishing between acute osteomyelitis and chronic osteomyelitis. Osteomyelitis is an infective process that encompasses all of the bone (osseous) components, including the bone marrow. When it is chronic, it can lead to bone sclerosis and deformity. The cause is usually a bacterial infection, but rarely can be a fungal infection.
Treatment of bacterial osteomyelitis often involves both antimicrobials and surgery. In those with poor blood flow, amputation may be required. Treatment outcomes of bacterial osteomyelitis are generally good when the condition has only been present a short time.
What can happen if Osteomyelitis is not treated?
If left untreated, this disorder can result in sepsis. The Third International Consensus Definition for Sepsis and Septic Shock (Sepsis-3) defines septic shock as a subset of sepsis in which particularly profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone.
Septic shock is a result of a systemic response to infection or multiple infectious causes. The pathophysiology of septic shock is not entirely understood, but it is known that a key role in the development of severe sepsis is played by an immune and coagulation response to an infection. Both pro-inflammatory and anti-inflammatory responses play a role in septic shock. Septic shock involves a widespread inflammatory response that produces a hypermetabolic effect. This is manifested by increased cellular respiration, protein catabolism, and metabolic acidosis with a compensatory respiratory alkalosis.
Most cases of septic shock are caused by Gram-positive bacteria, followed by endotoxin-producing Gram-negative bacteria, although fungal infections are an increasingly prevalent cause of septic shock. Toxins produced by pathogens cause an immune response; in Gram-negative bacteria, these are endotoxins, which are bacterial membrane lipopolysaccharides (LPS)
Patients with septic shock can be clinically identified by requiring a vasopressor to maintain a mean arterial pressure of 65 mm Hg or greater and having serum lactate level greater than 2 mmol/L (>18 mg/dL) in the absence of hypovolemia. This combination is associated with hospital mortality rates greater than 40%.
Septic shock may be regarded as a stage of SIRS (Systemic Inflammatory Response Syndrome), in which sepsis, severe sepsis and multiple organ dysfunction syndrome (MODS) represent different stages of a pathophysiological process.
If an organism cannot cope with an infection, it may lead to a systemic response - sepsis, which may further progress to severe sepsis, septic shock, organ failure, and eventually, result in death.