title: Assessment of contrast-enhanced computed tomography for imaging of cartilage during fracture healing.
abstract: Assessment of the early stages of fracture healing via X-rays and computed tomography is limited by the low radio-opacity of cartilage. We validated a method of contrast-enhanced computed tomography (CECT) for non-destructive identification of cartilage within a healing fracture callus. Closed, stabilized fractures in femora of C57BL/6 mice were harvested on post-operative day 9.5 and imaged ex vivo with micro-computed tomography (µCT) before and after incubation in a cationic contrast agent that preferentially accumulates in cartilage due to the high concentration of sulfated glycosaminoglycans in the tissue. Co-registration of the pre- and post-incubation images, followed by image subtraction, enabled two- and three-dimensional delineation of mineralized tissue, soft callus, and cartilage. The areas of cartilage and callus identified with CECT were compared to those identified with the gold-standard method of histomorphometry. No difference was found between the areas of cartilage measured by the two methods (p = 0.999). Callus area measured by CECT was smaller than, but strongly predictive of (R(2) = 0.80, p < 0.001), the corresponding histomorphometric measurements. CECT also enabled qualitative identification of mineralized cartilage. These findings indicate that the CECT method provides accurate, quantitative, and non-destructive visualization of the shape and composition of the fracture callus, even during the early stages of repair when little mineralized tissue is present. The non-destructive nature of this method would allow subsequent analyses, such as mechanical testing, to be performed on the callus, thus enabling higher-throughput, comprehensive investigations of bone healing.
authors.affiliation: Department of Biomedical Engineering, Boston University, Boston, MA, USA. lnmh@bu.edu
authors.forename: Lauren N M
authors.initials: LN
authors.lastname: Hayward
authors.forename: Chantal M J
authors.initials: CM
authors.lastname: de Bakker
authors.forename: Louis C
authors.initials: LC
authors.lastname: Gerstenfeld
authors.forename: Mark W
authors.initials: MW
authors.lastname: Grinstaff
authors.forename: Elise F
authors.initials: EF
authors.lastname: Morgan
mesh_terms: D000818:Animals; D002146:Bony Callus / Q000000981:diagnostic imaging*; D002356:Cartilage / Q000000981:diagnostic imaging; D003287:Contrast Media; D017102:Fracture Healing; D050723:Fractures, Bone / Q000000981:diagnostic imaging*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010619:Phenazines; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055114:X-Ray Microtomography
chemical_list: D003287:Contrast Media; D010619:Phenazines; C009195:safranine T