Chondroblastoma

Chondroblastoma is an uncommon benign cartilaginous neoplasm of the bone which is derived from primitive cartilage. It is seen most commonly in young age group, mainly 5-25 yrs. Men are affected more commonly than female. The neoplasm occurs in para articular region, predominantly involving the epiphyses and apophyses of the tubular long bones. Femur, humerus and tibia are more commonly affected. Radiographs show a well defined oval or spheroid osteolytic lesion, eccentric or central in location in the epiphyses or apophyses. It is surrounded by thin sclerotic margin which separates the lesion from the normal bone. Central calcified chondroid matrix is seen in around 30% cases. The surrounding metaphyses may show evidence of periostitis which is due to the inflammatory process accompanying chondroblastoma. On MRI, it shows low signal on T1 WI and variable signal on T2. A peripheral rim of low signal is seen in all sequences. Surrounding marrow edema and periostitis is due to the inflammatory reaction elicited by this lesion and loose attachment of the periosteum in childhood. These inflammatory changes may make the appearance of this benign lesion as an aggressive process and have to be kept in mind to avoid misinterpretation. The diagnosis of chondroblastoma is made with surgical biopsy, and the mainstay of treatment is curettage and bone chip grafting. The frequency of recurrence after these procedures is approximately 25%. Recurrence is more common among patients with open physeal plates. If left untreated, chondroblastoma can enlarge, undergo cortical breakthrough, and invade the adjacent joint. Surgical complications are rare unless the patient is skeletally immature, in which case physeal injury and subsequent growth arrest can occur.