Periosteal reaction

A periosteal reaction, also known as a periosteitis, is a non specific radiographic finding that occurs with periosteal irritation. Periosteal reactions may be broadly characterized as benign or aggressive, or more specifically broken down by pattern.

Classification

Benign versus aggressive

Periosteal reaction may be classified as benign or aggressive (note: not benign and malignant) based on the time course of the initiating process.

Benign periosteal reaction

Low-grade chronic irritation allows time for the formation of normal or near-normal cortex. The cortex will be thick and dense and have a wavy or uniform appearance.

Benign periosteal reactions can be seen in callus formation in a fracture or with slowly growing tumours.

Aggressive periosteal reaction

Rapid irritative processes do not allow the periosteum time to lay down and consolidate new bone to form normal cortex. The cortex may appear lamellated, amorphous, or sunburst-like.

Aggressive periosteal reactions can not only be seen with malignant tumours, but also with more benign processes like infection, eosinophilic granuloma (Langerhan’s cell histiocytosis), aneurysmal bone cyst, osteoid osteoma, and trauma.

Morphological classification of periosteal reactions

More specific classification of periosteal reactions can be made to narrow the differential diagnosis.

• single layer
• multilayered
• solid
• spiculated
  • perpendicular (hair-on-end)
  • divergent (sunburst)
  • sloping (velvet)
• disorganised / complex
• Codman triangle