Osteomyelitis

Question 1

Define Osteomyelitis

Answer 1

Osteomyelitis is an inflammatory condition of bone caused by an infecting organism, most commonly Staphylococcus aureus.

Question 2

Explain the aetiology of Osteomyelitis

Answer 2

• Acute OM: develops within days or weeks
• Chronic OM: develops slowly (over months or years) and is associated with avascular bone necrosis and sequestrum formation (necrotic bone fragment that has become detached from the original bone)

Hematogenous osteomyelitis: usually monomicrobial

• Due haematogenous dissemination of pathogen
• Common in children and Immunosupressed
• Can be caused by IVDU

Exogenous osteomyelitis: usually polymicrobial

• Post-traumatic: infection following deep injury which causes direct inoculation (penetrating injury, open fractures, severe soft tissue injury)
• Contiguous: spread of infection from adjacent tissue
  
  • Secondary to infected foot ulcer in diabetic patients
  • Cellulitis
  • Iatrogenic (e.g. postoperative infection of a prosthetic joint implant)

Question 3

Explain the risk factors for OM

Answer 3

• Traumatic penetrating injury
• Recent surgery (orthopaedic or not)
• Staph aureus is MOST COMMON causative organism
• IVDU (Pseudomonas & Staph aureus is common
• Sickle Cell Anaemia (Salmonella is most common organism)
• Diabetic ulcer (staph epidermis is common)
• Immunosuppression (HIV, Chemotherapy)
• HIV infection

Question 4

Epidemiology

Answer 4

Type of infection varies with age.

• Common in young children & affects the long bones.
• In adults, much more common in the vertebrae e.g., Pott’s disease (TB).

Question 5

Presenting symptoms

Answer 5

• Painful
  
  • Non-specific pain
  • Local back pain (if vertebral osteomyelitis)
• Fever
• Malaise

Question 6

Signs on Physical Examination

Answer 6

• Limp/Antalgic gait/reluctance to bear weight
• Tenderness, redness and swelling
• Paravertebral tenderness (if vertebral OM)
• Reduced ROM
• Diabetic foot ulcer
  
  • these patients may not report pain - use the Probe to Bone test
  • If you can palpate the bone with a probe, this is indicative of osteomyelitis

Question 7

Investigations for OM

Answer 7

• ESR/CRP: Raised indicating infection/inflammation
• FBC: Raised WCC
• Blood culture: Identifies offending organism
• Plain x-ray:
  
  • Early stages (< 2 weeks of symptoms onset): typically no pathological findings
  • Later stages: bone destruction, sequestrum formation, periosteal reactions

Question 8

Management

Answer 8

• Need to eradicate sequestrum to allow bone to completely heal
• management is with long-term (6 weeks) course of antibiotics –> IV Flucloxacillin is given
• If due to infected joint prosthesis, 2-stage revision is indicated