Introduction
Osteomyelitis refers to infection of the bone and/or bone marrow. It can occur in both adults and children but is more common in the latter. It is commonly caused by Staph A, Pseudomonas, E. coli or Streptococci. It is pyogenic (pus producing) and this contributes to bone death. In children the metaphysis of long bones is often the site of infection.
Osteomyelitis can be acute or chronic.
Acute Osteomyelitis
Haematogenous osteomyelitis
- Disease of childhood
- Pathogenesis: Organisms (e.g. Staphylococcus Aureus) reach bone via the bloodstream from a septic focus elsewhere (e.g. a boil in the skin). They invade the bone and the body initiates a response but its effectiveness is lessened due to the bones inability to allow swelling so pus collects below the periosteum. The Metaphysis is the major site of infection and the epiphysis acts as a barrier to its spread. If the metaphysis is in the joint capsule (e.g. in the elbow) then acute pyogenic arthritis can occur. Bones most commonly affected are the tibia, femur and humerus
- Symptoms: Acute illness with extreme pain & tenderness over the affected bone. Symptoms may vary greatly and can also include:
- Fever
- Erthema & swelling
- Unwillingness to move limb
- Signs: Look for a source of infection (e.g. a boil) and pyrexia with tenderness over the affected bone. There should be a good range of movement unless the infection has spread to the joint
- Investigations: Positive blood cultures and leucocytosis with raised ESR and CRP. Blood cultures positive in 60% Early x-rays will be normal. Later x-rays (>2 weeks) will show loss of density, diffuse rarefaction of the metaphyseal area and new bone outlining the raised periosteum
- Treatment: Rest and IV antibiotics (e.g. flucloxacillin and fusidic acid, or vancomycin and cefotaxime, until the organism is identified) for approximately 4-6 weeks. Surgical drainage of any abscesses and removal of sequestra (pieces of dead bone) also must be considered and can reduce pain and reduce the likelihood of ischaemic necrosis
- Complications: Septicaemia, acute pyogenic arthritis, growth retardation, progression to chronic osteomyeltitis. Patients may be left with ‘dead space’ in the bones leaving them prone to fractures, septic arthritis and deformity.
Osteomyelitis following an open fracture or surgical operation
- Pus discharges through the wound rather than collecting below the periosteum
- There is visible pus and redness with less severe pain (no pressure build up)
- Treatment is to ensure adequate pus drainage and antibiotics but it often becomes chronic
Chronic Osteomyelitis
- Persistence of acute osteomyelitis after treatment
- Pathogenesis: Usually caused by Staphylococcus Aureus but can be Streptococci/Pneumococci. Commonly affects the ends of long bones but can affect the whole length
- Symptoms: Intermittent tenderness over the bone and pyrexia. There may be a sinus track leading to the skin surface
- Investigations: Radiography shows dense bone with patchy sclerosis giving a honeycomb appearance. CT scans can be performed to look for abscess cavities
- Treatment: Surgical drainage of the pus and antibiotics
- Complications: Pathological fractures and amyloid disease