Osteomyelitis refers to inflammation in a bone and bone marrow, usually caused by bacterial infection.
Haematogenous osteomyelitis refers to when a pathogen is carried through the blood and seeded in the bone. This is the most common mode of infection. Alternatively, osteomyelitis can occur due to direct contamination of the bone, for example, at a fracture site or during an orthopaedic operation.
Staphylococcus aureus causes most cases of osteomyelitis.
Osteomyelitis can be acute or chronic. Patients may develop recurring or chronic infections after treatment for acute osteomyelitis.
Risk Factors
The key risk factors for developing osteomyelitis are:
- Open fractures
- Orthopaedic operations, particularly with prosthetic joints
- Diabetes, particularly with diabetic foot ulcers
- Peripheral arterial disease
- IV drug use
- Immunosuppression
Infection in a prosthetic joint is a big problem. This occurs in around 1% of joint replacements, and extensive measures are taken to prevent it, such as perioperative prophylactic antibiotics. It is more likely to occur in revision surgery rather than during the initial joint replacement.
Presentation
The typical presentation of osteomyelitis is with:
- Fever
- Pain and tenderness
- Erythema
- Swelling
The presentation of osteomyelitis can be quite non-specific, with generalised symptoms of infection such as fever, lethargy, nausea and muscle aches.
Investigations
X-rays often do not show any changes, particularly in early disease. They cannot be used to exclude osteomyelitis. The potential signs of osteomyelitis on an x-ray are:
- Periosteal reaction (changes to the surface of the bone)
- Localised osteopenia (thinning of the bone)
- Destruction of areas of the bone
MRI scans are the best imaging investigation for establishing a diagnosis.
Blood tests will show raised inflammatory markers (e.g., WBC, CRP and ESR).
Blood cultures may be positive for the causative organism.
Bone cultures can be performed to establish the causative organism and the antibiotic sensitivities.
Management
Management involves a combination of:
- Surgical debridement of the infected bone and tissues
- Antibiotic therapy
Prolonged courses of antibiotics are required to treat osteomyelitis. The BNF page on osteomyelitis recommends for acute osteomyelitis:
- 6 weeks of flucloxacillin, possibly with rifampicin or fusidic acid added for the first 2 weeks
Alternatives to flucloxacillin are:
- Clindamycin in penicillin allergy
- Vancomycin or teicoplanin when treating MRSA
Chronic osteomyelitis usually requires 3 months or more of antibiotics.
Osteomyelitis associated with prosthetic joints (e.g., a hip replacement) may require complete revision surgery to replace the prosthesis.
Last updated August 2021
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