Osteomyelitis

What it is

Osteomyelitis is infection of bone. The x-ray shows osteolytic lesions and cysts, destruction of the periosteum and sequestrum formation. In a long bone the osteolytic destruction may be extensive and run through the shaft, with periosteal thickening and elevation over the proximal part of the bone.

Causes and risk

Named causes are sickle cell disease, infection secondary to skin lesions such as the ulcers of diabetes, and open fracture. Background conditions that make a person susceptible are:

• Diabetes
• IV drug users
• Immunocompromised patients, in whom pseudomonas and fungal species are common
• Open fractures

Staphylococcus aureus is the organism most often responsible, and it is the gram positive cocci that most often cause pediatric osteomyelitis and septic arthritis alike. The two organisms most often named are Staphylococcus aureus and group A streptococcus. In sickle cell disease Salmonella is the other likely organism, and in diabetes the infection is generally polymicrobial.

How it presents

Fever with pain and swelling of one limb, and inability to bear weight on it, is the usual picture; CRP and the white cell count are raised. Disease in a person with diabetes may instead show a draining sinus tract at the ankle together with fever and leg pain. Because septic arthritis and sickle cell pain crisis give the same picture of knee pain and swelling with fever in a person with sickle cell disease, all three sit together on the differential.