Abstract: Objective   To investigate the three-dimensional CT features and differential points of chondroblastoma (CB) and primary aneurysmal bone cyst (ABC).    Methods   The three-dimensional CT findings and clinical data of 22 patients of simple CB, 5 patients of CB secondary aneurysmal bone cyst and 24 patients of primary ABC confirmed by surgical pathology and immunohistochemistry were retrospectively analyzed.    Results    The three groups showed single osteolytic bone destruction with clear boundary on three-dimensional CT. The maximum diameters of lesions in CB group and CB secondary aneurysmal bone cyst group were smaller than that in ABC group (P<0.05). The incidences（54.5%,86.4%,50%,77.3%,54.5%）of irregular bone, eccentricity, calcification, adjacent articular surface, and penetration of cortical bone in CB group were higher than those in ABC group（20.8%,29.2%,8.3%,4.2%,25.0%）(P<0.05), and the incidences(40.9%,18.2%) of expansion growth and pathological fracture were lower than those of ABC group(75.0%,45.8%) (P<0.05). However, there was no significant difference in the incidence of sign of lobulation, marginal sclerosis, bone crest and cortical involvement between CB group and ABC group (P>0.05).    Conclusions    The anatomical location of the lesions and the CT three-dimensional signs are of great value in the differential diagnosis of CB and ABC.

Key words: Chondroblastoma; ,  ,  Aneurysmal bone cyst; ,  ,  Differential diagnosis; ,  Computed tomography