Osteomyelitis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Osteomyelitis is an infection of the bone, typically caused by bacteria, that can lead to the destruction of bone tissue. It can be acute or chronic and may affect any bone in the body.

Aetiology

Osteomyelitis is usually caused by:

• Bacteria: Staphylococcus aureus is the most common pathogen.
• Fungi: Less commonly, fungal infections can lead to osteomyelitis.

The infection can reach the bone through:

• Hematogenous spread (through the bloodstream)
• Direct inoculation from trauma or surgery
• Contiguous spread from nearby infections

Pathophysiology

The pathophysiology of osteomyelitis involves:

• The pathogen reaches the bone and proliferates, causing an inflammatory response.
• This leads to increased pressure within the bone, reducing blood flow and causing bone necrosis.
• Sequestrum (dead bone) may form, and the body attempts to wall off the infection, leading to involucrum (new bone formation).

Risk Factors

• Diabetes
• Peripheral vascular disease
• Recent trauma or surgery
• Intravenous drug use
• Immune suppression (e.g., HIV, chemotherapy)
• Presence of prosthetic devices

Signs and Symptoms

The signs and symptoms of osteomyelitis include:

• Localized bone pain and tenderness
• Swelling and redness over the affected area
• Fever and chills
• Restricted movement of the affected limb
• Drainage of pus from the area

Investigations

Specific investigations to diagnose osteomyelitis include:

• Blood tests: Elevated white blood cell count, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR).
• Blood cultures: To identify the causative organism if bacteremia is present.
• Imaging: X-ray, MRI, or CT scan to assess bone involvement and extent of infection.
• Bone biopsy: Histological examination and culture to identify the pathogen and guide antibiotic therapy.

Management

Primary Care Management

• Initial assessment: Recognition of symptoms and prompt referral to secondary care for further evaluation and management.
• Empirical antibiotics: Initiated if there is a strong suspicion of osteomyelitis, in consultation with secondary care.

Specialist Management

• Intravenous antibiotics: Targeted based on culture results, typically for a prolonged course (4-6 weeks).
• Surgical intervention: Debridement to remove necrotic bone and drain abscesses, and in some cases, removal of any prosthetic material.
• Monitoring and follow-up: Regular blood tests to monitor inflammatory markers and imaging to assess the resolution of infection.
• Management of underlying conditions: Optimising control of diabetes, vascular disease, or other predisposing factors.

References

1. NHS (2024) Osteomyelitis. Available at: https://www.nhs.uk/conditions/osteomyelitis/ (Accessed: 24 June 2024).
2. Centers for Disease Control and Prevention (2024) Osteomyelitis. Available at: https://www.cdc.gov/osteomyelitis/ (Accessed: 24 June 2024).
3. World Health Organization (2024) Osteomyelitis. Available at: https://www.who.int/health-topics/osteomyelitis (Accessed: 24 June 2024).
4. British Medical Journal (2024) Osteomyelitis: clinical features, diagnosis, and management. Available at: https://www.bmj.com/content/350/bmj.h2044 (Accessed: 24 June 2024).

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