MRSA Bone Infection (Osteomyelitis)

Overview

Osteomyelitis is an infection in the bone. Osteomyelitis is concerning because these infections are difficult to treat, usually require weeks of IV antibiotics, and often require surgical debridement of the infected bone. Debridement is the process whereby necrotic (dead) and/or infected bone is removed.

• Osteomyelitis may occur in the following circumstances:
  • A superficial infection over a bone – infects the underlying bone. 
  • Bacteria circulating in the bloodstream – infect a bone by lodging themselves in blood vessels that enter the bone. The infection may track to the skin surface if the bone is in close proximity to the skin.
• These patients frequently have a depressed immune system. 

Examination

• Classic presentation is a tender, deep, draining wound located over a bone. But note: osteomyelitis can occur without pain, and without a superficial wound. 
• Other symptoms may include fever, weakness, body aches and fatigue.

Diagnosis

The diagnosis of osteomyelitis is notoriously difficult. It is determined clinically via the history and physical, with the aid of diagnostic testing.

• X-rays start the diagnostic workup. The infected bone may show erosion (worn area) at the site of infection. 
• Blood work is often ordered.  
  • A blood count (CBC) provides evidence for infection, when the white blood cells are elevated. 
  • Sedimentation rate (ESR) and C-reactive protein (CRP) are two separate tests for inflammation, and are often elevated with an infection. 
  • Note: the above blood tests provide evidence for infection, but do not diagnose infection.
• MRI or CT scans provide the best evidence for osteomyelitis, and are often necessary. 
• Tagged white blood cell studies are used infrequently, but can be helpful in difficult cases. White blood cells (infection fighting cells) are removed from the patient via a routine blood draw. The cells are tagged with a radioisotope, and then injected back into the patient. The cells seek out infection, and can identify the infection site.  
• A bone biopsy may be performed. A bone biopsy has the potential to both verify osteomyelitis, and identify the causative bacteria. A fragment of bone is removed surgically from the suspected site of infection. The fragment is sent to the lab to be examined for signs of infection, and totest for infection. Successful testing enables you to know the exact bacteria causing the infection, and which antibiotics will best treat the infection.