II. Indications
- First line study in Osteomyelitis evaluation due to low cost and high availability
- Narrows Osteomyelitis differential diagnosis by ruling out other causes
- Metastases to bone
- Osteoporotic Fractures
III. Findings: Early
- Soft tissue swelling
- Periosteal reaction (Subperiosteal elevation)
IV. Findings: Later
- Osteolysis with cortical loss and bony destruction
- Typical appearance is the "rat bite" (lytic lesions) of destroyed bony cortex
- Lytic changes not visualized until 50-75% of bone matrix is destroyed
- Sequestra (islands of necrotic bone)
- Bone abscess (Brodie's abscess)
V. Efficacy
- Test Sensitivity: 62% (43-75% in Diabetic Foot Osteomyelitis)
- Test Specificity: 64% (65-83% in Diabetic Foot Osteomyelitis)
VI. Limitations
- Bone changes lag infection by 10-20 days
- XRay changes not seen until 40-70% bone resorbed
- Repeat XRay at 2 week intervals