Osteomyelitis

 

• Background

  Infection of a bone.

  Pathophysiology

  • Infection can come from direct/contiguous spread (cellulitis, abscess, trauma, surgery prosthesis), or haematogenous spread, which is commoner in kids, patients with urinary catheters, or TB.
  • Once infected, leukocytes enter bone, releasing enzymes which cause bone lysis and leave necrotic areas known as sequestra. New bone often forms around this.
  • Chronic osteomyelitis if >6 months of infection.

  Pathogens

  • Staph. aureus is the commonest cause in most patient groups.
  • Less common pathogens include Strep. pyogenes (kids), H. influenzae (kids), Gram negative bacilli (elderly), and Pseudomonas aeruginosa (IV drug users).
  • In sickle cell disease, Salmonella is the commonest cause.

• Signs and symptoms

  General features:

  • Local inflammation.
  • Pain
  • Slight effusion of neighbouring joints.
  • Systemic symptoms.
  • Can be asymptomatic in diabetes due to neuropathy.

  Vertebral osteomyelitis:

  • Localized spine inflammation. 'Cold' in TB.
  • Chronic back pain, which may be worse at rest and at night.
  • There is often associated discitis.

• Risk factors

  Portal for pathogen entry:

  • Trauma: open fracture or orthopedic surgery.
  • Surgical prostheses.
  • IVDU

  Diseases:

  • TB
  • Diabetes
  • PVD
  • Immunosuppression.
  • Alcoholism
  • Sickle cell disease.

• Investigations

  Bloods and microbiology:

  • ↑WBC/ESR/CRP.
  • Bone culture is gold standard.
  • Also culture blood, pus, and local joint effusion.
  • Look for cause e.g. urine.

  Imaging:

  • X-ray: dark area in bone, soft tissue swelling. Signs may be minimal in acute infection.
  • MRI provides clearer picture if diagnosis is uncertain.

• Management

  • Antibiotics for 6 weeks, IV then PO. Flucloxacillin ± fusidic acid or rifampicin in first 2 weeks.
  • Debridement to drain pus and remove sequestra if severe.
  • Chronic osteomyelitis may require 12 weeks of antibiotics and extensive surgery.

• Complications

  • Septic arthritis.
  • Fracture
  • Deformity