Cationic contrast‐enhanced computed tomography distinguishes between reparative, degenerative, and healthy equine articular cartilage

Abstract

Cationic contrast‐enhanced computed tomography (CECT) is a quantitative imaging technique that characterizes articular cartilage, though its efficacy in differentiating repair tissue from other disease states is undetermined. We hypothesized that cationic CECT attenuation will distinguish between reparative, degenerative, and healthy equine articular cartilage and will reflect biochemical, mechanical, and histologic properties. Chondral defects were created in vivo on equine femoropatellar joint surfaces. Within defects, calcified cartilage was retained (Repair 1) or removed (Repair 2). At sacrifice, plugs were collected from within defects, and at locations bordering (adjacent site) and remote to defects along with site‐matched controls. Articular cartilage was analyzed via CECT using CA4+ to assess glycosaminoglycan (GAG) content, compressive modulus (E eq), and International Cartilage Repair Society (ICRS) II histologic score. Comparisons of variables were made between sites using mixed model analysis and between variables with correlations. Cationic CECT attenuation was significantly lower in Repair 1 (1478 ± 333 Hounsfield units [HUs]), Repair 2 (1229 ± 191 HUs), and adjacent (2139 ± 336 HUs) sites when compared with site‐matched controls (2587 ± 298, 2505 ± 184, and 2563 ± 538 HUs, respectively; all p < .0001). Cationic CECT attenuation was significantly higher at remote sites (2928 ± 420 HUs) compared with Repair 1, Repair 2, and adjacent sites (all p < .0001). Cationic CECT attenuation correlated with ICRS II score (r = .79), GAG (r = .76), and E eq (r = .71; all p < .0001). Cationic CECT distinguishes between reparative, degenerative, and healthy articular cartilage and highly correlates with biochemical, mechanical, and histological tissue properties.

Composition, architecture and biomechanical properties of articular cartilage in differently loaded areas of the equine stifle

“…The current results emphasise the importance of the intricate architecture and interplay between cartilage structure and function. Other reports on the relation between the structure of cartilage and its biomechanics in the horse and other species, including humans, are in line with our results 8,12,39,40 . Still, studies on equine cartilage repair techniques commonly evaluate the quality of the obtained repair tissue by means of histological and biochemical analyses only failing to test the repair tissue structurally and even more important functionally, that is, biomechanically 13 .…”

“…Other reports on the relation between the structure of cartilage and its biomechanics in the horse and other species, including humans, are in line with our results. 8,12,39,40 Still, studies on equine cartilage repair techniques commonly evaluate the quality of the obtained repair tissue by means of histological and biochemical analyses only failing to test the repair tissue structurally and even more important functionally, that is, biomechanically. 13 Our findings once more stress the important relationship between loading and biomechanical functionality of articular cartilage and how this is achieved by nature through site-dependent adaptations in both composition and architecture of the tissue.…”

Dual‐contrast micro‐CT enables cartilage lesion detection and tissue condition evaluation ex vivo

“…The feasibility of clinical use of the BiNPs will be studied in future projects. One proposed alternative is to substitute ioxaglate with a cationic agent that diffuses into cartilage proportionally to the PG content 39,40 . Moreover, the diagnostic sensitivity of the cationic agent can be further enhanced with a non‐ionic compound, nullifying the variation in the diffusion caused by changes in tissue water content and permeability 41,42 .…”

“…One proposed alternative is to substitute ioxaglate with a cationic agent that diffuses into cartilage proportionally to the PG content. 39 , 40 Moreover, the diagnostic sensitivity of the cationic agent can be further enhanced with a non‐ionic compound, nullifying the variation in the diffusion caused by changes in tissue water content and permeability. 41 , 42 Our results form a good basis to proceed on this path, as these show clear differences in ioxaglate partition values between lesions and healthy tissue, even though cationic agent have exhibited stronger correlation with PGs ( R 2 = 0.83) than negatively charged agents ( R 2 = 0.20).…”