The frequency and diagnostic significance of periostitis in chondroblastoma.

A study was performed to determine the frequency of periosteal reaction associated with chondroblastoma, to investigate the underlying pathophysiology of the periosteal reaction, and to postulate the clinical importance of this radiographic observation. Two hundred fourteen histologically proved chondroblastomas were reviewed and observed for the presence or absence of periosteal reaction and for radiographic changes that might explain the cause of the periosteal reaction. A similar review was performed on 30 other epiphyseally centered lesions of various causes. A distinctive thick, solid periosteal reaction distal to the chondroblastoma was present in 47% of all chondroblastomas and 57% of chondroblastomas present in long bones (excluding the greater trochanter). No periosteal reaction was observed in any of the 30 epiphyseally centered lesions of other causes. When available for observation, plain films showed inflammatory changes in the joint surrounding the chondroblastoma, bone scintigraphy showed tracer uptake similar to that observed in inflammatory lesions and aggressive neoplasms, and MR images showed change in the marrow surrounding the chondroblastoma consistent with edema. This suggests an inflammatory reaction to the chondroblastoma, rather than mechanical stress across a weakened epiphysis, as the cause of the periostitis. We conclude that frequently the chondroblastoma produces a distinctive thick solid or layered periosteal response distant from the lesion along the diametaphyseal shaft. Observation of this unique periosteal response may help to distinguish chondroblastoma from other epiphyseally centered lesions.