Contrast-Enhanced Micro–Computed Tomography in Evaluation of Spontaneous Repair of Equine Cartilage

Abstract

Objective:Contrast-enhanced computed tomography (CECT) has been introduced for the evaluation of cartilage integrity. Furthermore, CECT enables imaging of the structure and density of subchondral bone. In this laboratory study, we investigate the potential of microCECT to simultaneously image cartilage and subchondral bone for the evaluation of tissue healing.Design:Osteochondral lesions (Ø = 6 mm) were surgically created in equine intercarpal joints (n = 7). After spontaneous healing for 12 months, the horses were sacrificed and osteochondral plugs (Ø = 14 mm), including the repair cartilage and adjacent intact tissue, were harvested. The nonfibrillar and fibrillar moduli and the permeability of cartilage were determined using indentation testing. Contrast agent diffusion into the samples was imaged for 36 hours using high-resolution CT. Results from CECT, mechanical testing, and microscopic analyses were compared and correlated.Results:The contrast agent diffusion coefficient showed a significant (P < 0.05) difference between the repair and adjacent intact tissue. MicroCECT revealed altered (P < 0.05) bone volume fraction, mineral density, and microstructure of subchondral bone at the repair site. The contrast agent diffusion coefficient correlated with the moduli of the nonfibrillar matrix (R = −0.662, P = 0.010), collagen fibril parallelism index (R = −0.588, P = 0.035), and glycosaminoglycan content (R = −0.503, P = 0.067). The repair cartilage was mechanically and structurally different from adjacent intact tissue (P < 0.05).Conclusions:MicroCECT enabled simultaneous quantitative evaluation of subchondral bone and monitoring of cartilage repair, distinguishing quantitatively the repair site from the adjacent intact tissue. As the only technique able to simultaneously image cartilage and determine subchondral bone mineral density and microstructure, CECT has potential clinical value.

In vivo diagnostics of human knee cartilage lesions using delayed CBCT arthrography

“…This would allow delayed CBCT arthrography with only two image acquisitions, that is, the arthrographic and delayed images. In previous studies, when applying CECT in vitro the native image (without contrast agent) has been subtracted from the contrast enhanced images . The subtraction has been done to determine the contrast agent diffusion into the cartilage as quantitatively as possible.…”

In vivo comparison of delayed gadolinium-enhanced MRI of cartilage and delayed quantitative CT arthrography in imaging of articular cartilage

“…Contrast-enhanced CT, an analogous X-ray technique to dGEMRIC, also employs contrast agent (e.g., anionic ioxaglate, charge À1). There are a range of in vitro studies in which the contrast-enhanced CT technique has shown its potential in assessment of GAG content 24e28 and biomechanical properties 24,29 of cartilage, as well as in detection of cartilage injuries 30,31 . Contrast-enhanced CT, referred to as delayed quantitative CT arthrography (dQCTA) in the present study, has recently been tested in vivo 32 , but it has not been thoroughly validated in clinical settings.…”

Osteochondral Repair: Evaluation with Sweep Imaging with Fourier Transform in an Equine Model

“…Landmark cuts were created before storage at 220°C. The samples in this study are from a larger project in which the equine model was used to investigate spontaneous healing in the horse (16)(17)(18).…”

“…Sample blocks covering the lesion site were processed for histologic examination by using procedures described earlier (16). The pieces were embedded in paraffin and cut into 3-mm-thick microscopic slices that were stained with cationic Safranin-O dye for quantification of glycosaminoglycan polyanions of proteoglycans (20).…”