Periosteal reaction for the Radiology Residents

Periosteal reaction for the residents, this is what you should keep in mind while reporting a skeletal case.

With slow-growing processes, the periosteum has time to respond to the process. Therefore,  it can produce new bone just as fast as the lesion is growing-solid, uninterrupted periosteal reaction.
 


With rapidly growing processes, the periosteum cannot produce new bone as fast as the lesion is growing. Therefore, rather than a solid pattern of new bone formation, we see an interrupted pattern. This may result in a pattern of one or more concentric shells of new bone over the lesion-lamellated or "onion-skin" periosteal reaction.




If the lesion grows rapidly but steadily, the periosteum will not have enough time to lay down even a thin shell of bone, and the pattern may appear quite different. In such cases, the tiny fibers that connect the periosteum to the bone (Sharpey's fibers) become stretched out perpendicular to the bone. When these fibers ossify-"sunburst" or "hair-on-end" periosteal reaction.

Rapidly growing processes - Codman's triangle. When a process is growing too fast for the periosteum to respond with even thin shells of new bone, sometimes only the edges of the raised periosteum will ossify.