Epiphyseal involvement in osteosarcoma.

Plain radiography and magnetic resonance (MR) imaging were used to assess the extent of transphyseal involvement in 15 consecutive patients with long bone osteosarcoma and nonfused epiphyses. The findings were correlated with those from surgical and microscopic pathologic examinations. There were no cases of false-positive findings with either MR imaging or plain radiography. Conventional radiography accurately helped predict transphyseal spread in only nine of 15 cases (60%). Spread to the epiphysis was present in 12 of the 15 cases (80%) and was accurately predicted with MR imaging in all 12 cases. This finding contradicts the common misconception that the physis acts as a "barrier" to tumor spread.