Spiculated Periosteal Reaction: Pathophysiology

The spiculated pattern of periosteal reaction is an aggressive form of periosteal in which spicules of bone extend perpendicularly (hair-on-end) or radially (sunburst) away from the cortex. The hair-on-end type is suggestive of Ewing sarcoma, but can be seen in osteosarcoma, osteomyelitis, leukemia, lymphoma. The sunburst type is characteristically seen in osteogeosarcoma, but can also be seen with Ewing sarcoma, and hemangioma. Bone metastases, most commonly from prostate carcinoma, can also produce a spiculated pattern of periosteal reaction.

The appearance has to do with the way the periosteum is attached to the cortex. Millions of fibrous bands, called Sharpey's fibers, connect the periosteum to the cortex. New bone forms along these fibers after the periosteum is elevated. The spaces between these bony pillars can be invaded by blood vessels, and more bone can grow along these vessels.

The mechanism of this bone formation is not intuitive. It was thought that osteoblasts in the tumor are responsible for the bone formation. However, the reaction occurs in the soft tissue mass of osteosarcoma, a place where differentiated osteoblasts are not seen. In addition, spiculated periosteal reaction can also be seen in tumors that don't have osteoblasts.

An animal model of sunburst periosteal reaction has suggested a mechanism. Hamster ovary cells were transfected with bone morphogenic protein-4 and injected into the bone of nude mice. The resulting tumors were then found to have a periosteal reaction with a sunburst appearance. This has led to the suggestion that the bone inducing factors secreted by tumors lead to induction of osteoblastic activity and subsequent periosteal bone formation.

The images above are from a young man with osteosarcoma.

References

• Bloom RA, Libson E, Husband JE, Stoker DJ. The periosteal sunburst reaction to bone metastases. A literature review and report of 20 additional cases. Skeletal Radiol. 1987;16(8):629-34. Review.
• Rana RS, Wu JS, Eisenberg RL. Periosteal reaction. AJR Am J Roentgenol. 2009 Oct;193(4):W259-72.
• Wyche LD, de Santos LA. Spiculated periosteal reaction in metastatic disease resembling osteosarcoma. Orthopedics. 1978 May-Jun;1(3):215-21.
• Yoshikawa H, Shimizu K, Nakase T, Takaoka K. Periosteal sunburst spiculation in osteosarcoma. A possible role for bone morphogenetic protein. Clin Orthop Relat Res. 1994 Nov;(308):213-9.