Mechanical asymmetry during articulation of tibial and femoral cartilages: Local and overall compressive and shear deformation and properties

Abstract

During knee movement, femoral cartilage articulates against cartilage from the tibial plateau, and the resulting mechanical behavior has yet to be fully characterized. The objectives of this study were to determine 1) the overall and depth-varying axial and shear strains, and 2) the associated moduli, of femoral and tibial cartilage during the compression and shearing of apposing tibial and femoral samples. Osteochondral blocks from human femoral condyles (FC) characterized as normal and donor-matched lateral tibial plateau (TP) were apposed, compressed 13%, and subjected to relative lateral motion. When surfaces began to slide, axial (−Ezz) and shear (Exz) strains and compressive (E) and shear (G) modulus, overall and as a function of depth, were determined for femoral and tibial cartilage. Tibial −Ezz was ~2-fold greater than FC −Ezz near the surface (0.38 versus 0.22) and overall (0.16 versus 0.07). Near the surface, Exz of TP was 8-fold higher than that of FC (0.41 versus 0.05), while overall Exz was 4-fold higher (0.09 versus 0.02). For TP and FC, −Ezz and Exz were greatest near the surface and decreased monotonically with depth. E for FC was 1.7-fold greater than TP, both near the surface (0.40 versus 0.24MPa) and overall (0.76 versus 0.47MPa). Similarly, G was 7-fold greater for FC (0.22MPa) than TP near the surface (0.03MPa) and 3-fold higher for FC (0.38MPa) than TP (0.13MPa) overall. These results indicate that tibial cartilage deforms and strains more axially and in shear than the apposing femoral cartilage during tibio-femoral articulation, reflecting their respective moduli.

Continuous multilayered composite hydrogel as osteochondral substitute

“…The sample with the lowest ratio (nHA/PVA 0.010) showed poor rheological properties for the foreseen application. In fact, its complex modulus G* was 1000 6 25 Pa whereas both the other two samples, nHA/PVA 0.02 and nHA/PVA 0.015, showed a main G* of about 22 6 0.3 kPa, close to the human tibial cartilage G* (G*: 0.03 6 0.003 MPa 13 ). Thus, the sample containing the lower suitable amount of nHA (nHA/PVA molar ratio of 0.015) was chosen to realize the first layer of the multilayered hydrogel.…”

“…The same procedure was then applied to crosslink a third layer, which was produced with a greater PVA/STMP molar ratio (2:1). Each layer composition was chosen to obtain a multilayered material with a gradient of water content and rheological properties similar to that of human cartilage 13,14 Samples characterization For infrared absorption analysis in attenuated total reflection (ATR) mode, hydrogels were partially dried in the air and analyzed using a Bruker ALPHA FT-IR spectrometer equipped with a diamond unit, to collect 64 scans in the range 4000-400 cm 21 at a resolution of 4 cm 21 . Background correction was operated with OPUS software.…”

Computational investigation of in situ chondrocyte deformation and actin cytoskeleton remodelling under physiological loading

“…Table Captions Table 1 Nominal strain components applied to the RVE based on the experimentally measured strains fields from the study of Wong & Sah [13]. Femoral condyle and tibial plateau strain components are based on strains from Wong & Sah [7]. Strains are also expressed in terms of the maximum ( ) and minimum ( ) principal strains, and the principal direction (φ).…”

“…In the case of dynamic loading, nominal strains are applied at frequency of 1 Hz, which is within the range of normal adult cadence [52]. Again, strain values based on the study of Wong and Sah [13] are chosen as the dynamic loading cases, with the exception of simulations investigating the effect of the PCM and cartilage anisotropy, in which strain values are based on the study of Wong and Sah [7] ( Table 1). …”

“…Previous studies have experimentally determined local strains during cartilage-oncartilage articulation [7,8]. In addition, Wong et al [9] have shown that shear strain in degenerated cartilage is markedly increased near the surface due to both increased friction and a reduction in the mechanical properties of the tissue.…”