Osteomyelitis

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

Definition

Osteomyelitis is an infection of the bone, usually caused by bacteria, leading to inflammation, bone destruction, and potential complications such as chronic infection or sepsis.

Aetiology

  • Haematogenous spread: common in children, bacteria enter the bloodstream and seed into bone.
  • Direct inoculation: trauma, surgery, open fractures.
  • Contiguous spread: infection from nearby soft tissue or joints (e.g., diabetic foot ulcers).
  • Common pathogens:
    • Staphylococcus aureus (most common).
    • Streptococcus species.
    • Pseudomonas aeruginosa (especially in IV drug users and post-surgical infections).
    • Salmonella species (associated with sickle cell disease).

Pathophysiology

  • Bacteria invade bone tissue, triggering an inflammatory response.
  • Leads to increased pressure within the bone, causing vascular compromise.
  • Can progress to necrosis, abscess formation, and chronic osteomyelitis.

Risk Factors

  • Diabetes mellitus (especially with peripheral neuropathy and ulcers).
  • Recent orthopaedic surgery or trauma.
  • IV drug use.
  • Immunosuppression (HIV, chemotherapy, steroids).
  • Sickle cell disease (higher risk of Salmonella osteomyelitis).
  • Peripheral vascular disease.

Signs and Symptoms

  • Localized bone pain and tenderness.
  • Swelling, warmth, and erythema over the affected area.
  • Fever, chills, and systemic symptoms (especially in acute cases).
  • Reduced range of motion if adjacent joints are affected.
  • Sinus tract formation with chronic drainage in chronic osteomyelitis.

Investigations

  • Full blood count (FBC): leukocytosis in acute infection.
  • Inflammatory markers: CRP and ESR typically elevated.
  • Blood cultures: to identify bacteraemia.
  • X-ray: may show periosteal reaction or bone destruction (late changes).
  • MRI: most sensitive for early detection of bone infection.
  • Bone biopsy and culture: gold standard for definitive diagnosis.

Management

1. Empirical Antibiotic Therapy:

  • IV flucloxacillin for 4-6 weeks (first-line for MSSA).
  • Clindamycin or vancomycin if MRSA suspected.
  • Ciprofloxacin for Pseudomonas coverage in high-risk patients.

2. Surgical Management:

  • Debridement of necrotic bone in chronic or refractory cases.
  • Drainage of abscess if present.

3. Supportive Measures:

  • Optimisation of glycaemic control in diabetics.
  • Analgesia for pain control.
  • Wound care and offloading in foot ulcers.

4. Referral:

  • Orthopaedics: for surgical intervention if required.
  • Infectious diseases: for prolonged or refractory infections.
  • Diabetology: for management of diabetic foot osteomyelitis.
Infectious DiseasemypanotesOsteomyelitis