Posttraumatic growth-plate abnormalities: MR imaging of bony-bridge formation in rabbits.

The formation of a bony bridge across the growth plate was studied with magnetic resonance (MR) imaging, tomography, and histologic examination in 12 rabbits. Histologic studies performed 0-8 weeks after the creation of a defect in the physis demonstrated transphyseal bone formation with no evidence of cartilage repair. Gadolinium enhancement indicated the development of vascularity through the plate, which preceded the formation of a bony bridge. Enhancement was faint at 4 days after surgery, was inhomogeneous at 1 week, was maximal at 2 weeks, and decreased at 3 weeks and beyond as the lesion was replaced by bone. A dark rim representing bone deposition at the periphery of the lesion was seen at 2 weeks. At 4 weeks and beyond, the bridge was seen as a dark band of dense bone or as a wider area that was isointense with adjacent fatty marrow. Abnormality in the cartilage and development of transphyseal vascularity, which precede the formation of a bony bridge after trauma, can be detected with MR imaging.