Orthopaedics and Rheumatology: Osteomyelitis
Introduction
- Infection of the bone caused by pyogenic organisms
- Can be acute or chronic
Acute Osteomyelitis
Haematogenous osteomyelitis
o Disease of childhood
o 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
o Symptoms: Acute illness with extreme pain over the affected bone
o 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
o Investigations: Positive blood cultures and leucocytosis with raised ESR and CRP. Early x-rays will be normal. Later x-rays will show diffuse rarefaction of the metaphyseal area and new bone outlining the raised periosteum
o Treatment: Rest and IV antibiotics (usually flucloxacillin and fusidic acid until the organism is identified) for approximately 4 weeks. Locally, pus can be released to reduce pain and reduce the likelihood of ischaemic necrosis
o Complications: Septicaemia, acute pyogenic arthritis and growth retardation
Osteomyelitis following an open fracture or surgical operation
o Pus discharges through the wound rather than collecting below the periosteum
o There is visible pus and redness with less severe pain (no pressure build up)
o 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
Notes by Natasha Turley
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