Abstract
In this study, we combined quantitative ultrashort echo time (UTE) magnetic resonance (MR) imaging and an investigation by a probing device with tri-axial force sensor to seek correlations with mechanical properties of human patellar cartilage for in situ evaluation of biomechanical properties. Cartilage blocks (15 × 20 × 5 mm3) were dissected from the patella of six donors; 5 mm square regions of interest from the cartilage blocks were imaged using UTE-MR imaging sequences (T2* and magnetization transfer ratio (MTR)), and mechanical properties were measured using a micro indentation device. Then, the vertical reaction force on the cartilage surface was measured while push-probing forward 3 mm with the probing device at a 30° tilt to the horizontal plane. The results showed a positive correlation between stiffness/elastic modulus and each predictor variable (UTE-T2* (r = 0.240 and 0.255, respectively, UTE-MTR (r = 0.378 and 0.379, respectively), and probing device force (r = 0.426 and 0.423, respectively). Furthermore, multiple linear regression analysis showed the combination of the three predictors had stronger correlation (adjusted r2 = 0.314 (stiffness), 0.323 (elastic), respectively). Our results demonstrate the potential for these non- and less- invasive methods for in situ evaluation of the mechanical properties of cartilage tissue.
Highlights
In situ mechanical property investigation of articular cartilage tissue is one of the most important evaluations for both clinical and basic researches in the orthopaedic surgery
The current study aimed to investigate the correlations between the quantitative magnetic resonance (MR) images (UTE-MT and ultrashort echo time (UTE)-T2* mapping) and the force values measured by the probing device, and the mechanical property by the micro indentation test to establish an in situ evaluation of the biomechanical properties of cartilage tissue
UTE-MTR and UTE T2* values strongly correlated with histological grades (Mankin scores) of cartilage degeneration (UTE-MTR; r = −0.678, UTE-T2*; R = −0.501) [12]
Summary
In situ mechanical property investigation of articular cartilage tissue is one of the most important evaluations for both clinical and basic researches in the orthopaedic surgery. A preliminary study has shown that a vertical reaction force from the probe axis (induced by the probing device) to the surface of cartilage mimic samples (a polyvinyl alcohol hydrogel) while push-probing correlated with mechanical properties by a micro indentation test [21]. There is no report on whether the measured values by the probing device correlate with the mechanical property of human articular cartilage. The current study aimed to investigate the correlations between the quantitative MR images (UTE-MT and UTE-T2* mapping) and the force values measured by the probing device, and the mechanical property by the micro indentation test to establish an in situ evaluation of the biomechanical properties of cartilage tissue.
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