Cationic agent contrast-enhanced computed tomography imaging of cartilage correlates with the compressive modulus and coefficient of friction

Abstract

Objective The aim of this study is to evaluate whether contrast enhanced computed tomography (CECT) attenuation, using a cationic contrast agent (CA4+), correlates with the equilibrium compressive modulus (E) and coefficient of friction (μ) of ex vivo bovine articular cartilage. Methods Correlations between CECT attenuation and E (Group 1, n=12) and μ (Group 2, n=10) were determined using 7mm diameter bovine osteochondral plugs from the stifle joints of six freshly slaughtered, skeletally mature cows. The equilibrium compressive modulus was measured using a 4-step, unconfined, compressive stress relaxation test, and the coefficients of friction were determined from a torsional friction test. Following mechanical testing, samples were immersed in CA4+, imaged using μCT, rinsed, and analyzed for glycosaminoglycan (GAG) content using the DMMB assay. Results The CECT attenuation was positively correlated with the GAG content of bovine cartilage (R2= 0.87, p<0.0001 for Group 1 and R2= 0.74, p=0.001 for Group 2). Strong and significant positive correlations were observed between E and GAG content (R2= 0.90, p<0.0001) as well as CECT attenuation and E (R2= 0.90, p<0.0001). The CECT attenuation was negatively correlated with the three coefficients of friction: CECT vs. μstatic (R2=0.71, p=0.002), CECT vs. μstatic_equilibrium (R2=0.79, p<0.001), and CECT vs. μkinetic (R2=0.69, p=0.003). Conclusions CECT with CA4+ is a useful tool for determining the mechanical properties of ex vivo cartilage tissue as the attenuation significantly correlates with the compressive modulus and coefficient of friction.

Reinforcement of articular cartilage with a tissue-interpenetrating polymer network reduces friction and modulates interstitial fluid load support

“…Nine pairs of osteochondral cylindrical plugs (7 mm diameter, cartilage thickness ranging approximately 1–1.5 mm) were cored from the stifle joints of skeletally mature cows in a procedure similar to those reported previously 12, 37 using a diamond-tipped coring bit (Starlite Industries, Bryn Mawr, PA), irrigated with 0.9% saline at room temperature. Throughout experimentation, plugs were stored at 4°C in 400 mOsm sodium chloride solution containing protease inhibitor benzamidine hydrochloride (5 mM), GIBCO Antibiotic/Antimycotic (Invitrogen, Grand Island, NY), and calcium ion chelating agent ethylenediamine tetraacetic acid (5 mM).…”

Contrast-enhanced CT facilitates rapid, non-destructive assessment of cartilage and bone properties of the human metacarpal

“…Excised articular cartilage discs or osteochondral plugs are routinely used ex vivo to study cartilage functional properties (e.g., compressive stiffness) [7–12] and are commonly employed for ex vivo imaging studies, including delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) [13–15] and contrast-enhanced computed tomography (CECT) [9, 10, 16–18]. However, these ex vivo tissue models suffer from one or more of the following limitations.…”

“…Second, if the samples are not extracted from human cadavers, the tissue may not adequately represent the biochemical composition and mechanical properties [7] of human tissue, particularly in disease. Finally, the cartilage tissue is often degraded using enzymes to simulate an early-stage OA degenerated state, yet the pattern of tissue degradation does not often reflect the diseased tissue state [9, 10]. Therefore, more appropriate models for studying cartilage and subchondral bone changes present in joint diseases are warranted.…”

“…The underlying subchondral bone is also a suitable size for high-resolution imaging, thereby preventing the need for damaging the bone during sample extraction or disrupting the cartilage-subchondral bone interface – thus facilitating the simultaneous analysis of subchondral bone and cartilage. Furthermore, OA commonly occurs in human fingers [2, 19], including the metacarpophalangeal joint (MCPJ) [2, 19], which obviates the need for artificial cartilage degradation [9, 10]. Hence, the human metacarpal presents a cartilage surface with an ideal geometry for testing with native boundary conditions and a natural range of cartilage and bone health.…”

“…Both dGEMRIC [13] and CECT [9, 10, 20, 21] enable effective estimation of cartilage GAG content, however MRI is limited in its ability to examine bony changes. Therefore, we sought to use CECT imaging as method to examine the relationships between common cartilage and bone properties towards the development of the metacarpal as a new model for early-stage OA.…”