MR Imaging and Histologic Microvascular Photography of the Cartilage in Developing Bone

Objective To clarify which structures in the cartilage can be visualized on MRI.Materials and Methods MR images of the knee in 30 children (aged 2～14 years) were reviewed and correlated with histologic en bloc sections as well as microvascular photographs of the epiphyseal cartilage, the articular cartilage, the growth plate, the intra articular fat pad and the synovial membrane.Results MRI demonstrated the zone of chondroblasts in the articular cartilage and in the epiphyseal cartilage, the zone of hypertrophic chondrocytes and the main blood vessels within the epiphyseal cartilage. The zone of provisional calcification in the growth plate presented itself as a line of low signal intensity, while the zone of capillary blood vessels in the zone of primary spongiosa as a narrow strip with high signal intensity. In children aged 6～8 years, the communicating blood vessel, which connected the epiphysis with the diaphysis in the growth plate, appeared as a longitudinal tube with intermediate signal intensity, being in contrast to the surrounding fibrous tissue. Synovial thickening and the interstitial tissue, including blood vessels, in intra articular fat pad could be demonstrated on MRI as well.Conclusion Some minor structures in the cartilage of the developing bone can be identified on MRI, which is very helpful in the study of cartilage diseases in infants and children.