Viscoelasticity measurement of ex vivo bovine cartilage using Lamb wave method

Cartilage viscoelasticity changes with cartilage degeneration. Therefore, measurement of cartilage viscoelasticity could offer an alternative to traditional imaging methods for early diagnosis of osteoarthritis. In previous studies, we confirmed the feasibility of using the Lamb wave method (LWM) to assess the elasticity within a simulated cartilage-bone structures. The objective of the present study was to test the suitability of the LWM for measuring viscoelastic properties of ex vivo bovine tibial plateau cartilage. Theoretical and numerical analyses were performed to understand the viscoelastic Lamb wave propagation in cartilage and a suitable measurement range and loading frequency for the LWM were determined. The viscoelasticity of bovine cartilage was experimentally estimated to be 32.8 ± 0.50, 30.9 ± 0.50, and 31.9 ± 1.85 Pa • s for cartilage samples with thicknesses of 2.84 ± 0.02, 2.32 ± 0.03, and 2.01 ± 0.08 mm, respectively, which showed good repeatability during LWM measurements. However, cartilage elasticity was not sensitive to the viscoelastic Lamb wave speed. Indentation tests were also performed and cartilage elasticities were 0.88 ± 0.09, 1.03 ± 0.12, and 0.93 ± 0.09 MPa, respectively. This study validates the use of the LWM for measuring the viscoelasticity of ex vivo cartilage and provides a critical step toward the ultimate goal of measuring the viscoelasticity of cartilage in vivo.