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

Abstract

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.

Intramembranous ossification mechanism for bone bridge formation at the growth plate cartilage injury site

“…Our study indicated that infiltration of mesenchymal cells into the growth plate injury site preceded and/or coincided with the bone bridge formation. Consistently, presence of fibrous mesenchymal cells at the early stage after growth plate injury was also observed in previous studies [13,15].…”

“…Therefore, our study confirmed the rapid time course of bone bridge formation at the growth plate injury site, and was consistent with previous investigations that used a similar drill-hole injury model in rabbits, rats, and mice. These earlier studies reported either initial or full osseous bar formation at the injury site by 1-3 weeks post-surgery [5,9,13,15,16]. in a Salter type I fracture model of proximal tibia1 physis in young rats, bony bars were found at day 10 after fracture [20].…”

RECENT RESEARCH ON THE GROWTH PLATE: Mechanisms for growth plate injury repair and potential cell-based therapies for regeneration

“…The fibrogenic phase has been observed on days 3-7 post-injury in injured growth plate of rats, involving an influx of vimentin (mesenchymal cell marker)-immunopositive mesenchymal cells ), a response which is similar to the infiltration of mesenchymal cells following the inflammatory phase at bone fracture sites (Jaramillo et al 1990, Schindeler et al 2008. At the growth plate injury site, some of these cells were found to express growth factors including BMPs (Ngo et al 2006), plateletderived growth factor (PDGF) and FGF2 ) and receptors for BMPs and PDGF (Ngo et al 2006).…”

Assessing permeability alterations of the blood–bone marrow barrier due to total body irradiation: in vivo quantification with contrast enhanced magnetic resonance imaging

“…The immature bone marrow of the New Zealand white rabbit is a model well suited for the current study since hematopoietic marrow is found within the central skeleton and its MR appearance has been well described before. 32,33 In addition, good anatomical resolution can be achieved for rabbits using a clinical MR scanner, which would not have been possible for smaller rodents. Our findings still have to be confirmed in humans.…”