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Pathology - Osteomyelitis
I. Definition:
This section outlines the pathways of infection, crucial for understanding the diverse presentations of the disease.
I. Definition:
- Infection of a bone. This is the core concept – remember this first and foremost.
- Can occur at any age, but patterns exist:
- Acute hematogenous osteomyelitis: Primarily affects children (infection spreads through the bloodstream). This is a key age-related distinction.
- Adults can develop osteomyelitis through other routes (see Acquisition).
This section outlines the pathways of infection, crucial for understanding the diverse presentations of the disease.
- Hematogenous spread: Bloodstream infection reaching the bone (common in acute childhood cases). Understand this is the primary route in children.
- Penetrating trauma: Open fractures or wounds allowing direct bacterial entry into the bone. This highlights a mechanism of injury.
- Iatrogenic: Infection caused by medical procedures (e.g., joint replacement surgery, root canal). Remember that medical intervention itself can introduce infection.
- Direct spread: Infection from a neighboring site (e.g., diabetic foot ulcer). This shows that osteomyelitis can be a secondary complication.
- Staphylococcus aureus (S. aureus): The most common causative agent. This is the most important microbe to remember.
- Salmonella species: Predominant in patients with sickle cell disease. This is a specific risk factor to note. The underlying condition increases susceptibility.
- Inflammation: Infection triggers acute inflammation within the bone, leading to pus formation (suppurative inflammation). Inflammation is the body's response, but in this case it leads to bone damage.
- Sequestrum formation: Necrotic (dead) bone fragments are formed. Understand “sequestrum” as a key term representing dead bone.
- Chronic osteomyelitis: If the infection isn't eradicated, chronic inflammation leads to the formation of new bone around infected areas. This highlights the potential for a protracted, serious condition.
- Fever: A systemic indication of infection.
- Bone pain: Localized to the affected bone.
- Inability to weight-bear: Specifically relevant in children, impacting their mobility.
- Aggressive treatment is essential: This requires intravenous antibiotics to kill bacteria and surgical debridement (removal of necrotic bone) to clear the infection. The treatment strategy needs to be aggressive.
- Joint replacement complications: Osteomyelitis following joint replacement can result in prosthesis failure. This highlights a significant complication.
- Hematogenous spread is the most common route in children.
- Staphylococcus aureus is the most frequent causative agent.
- Sequestrum refers to dead bone fragments.
- Treatment requires intravenous antibiotics and surgical debridement.
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