Osteomyelitis

Investigations:

• Blood cultures recommended. If positive, repeat blood cultures to ensure clearance of bacteremia.

• Bone cultures recommended. Radiologically-guided or open biopsy for culture and histopathology in vertebral osteomyelitis (higher yield than blood cultures) is recommended except if blood cultures positive for S. aureus, S. lugdunensis, Enterobacterales, or Brucella species.

• CBC and differential, serum creatinine.

• ESR or CRP - low specificity for diagnosis but if initially elevated, may be useful to monitor response.

• Imaging: Plain x-ray +/- MRI, or bone scan +/- WBC scan.

  • MRI superior to x-ray and bone scan for early diagnosis of bone/joint infections

  • Spine MRI superior to CT scan for vertebral osteomyelitis and identification of epidural abscess. If MRI not available, alternative imaging includes spine gallium/Tc99 bone scan, CT or PET scan.

  • Bone scan may be falsely positive if recent trauma/aspiration of joint/superficial infection, WBC or gallium scan may improve specificity.

  • MRI abnormalities may persist long after successful treatment.  Repeat MRI not needed unless lack of clinical response, suspected treatment failure, or presence of undrained abscess.