Topographic features of nano-pores within the osteochondral interface and their effects on transport properties –a 3D imaging and modeling study

Behdad Pouran, Amir Raoof, D. A.Matthijs de Winter, Vahid Arbabi, Ronald L.A.W. Bleys, Frederik J. Beekman, Amir A. Zadpoor, Jos Malda, Harrie Weinans

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Abstract

Recent insights suggest that the osteochondral interface plays a central role in maintaining healthy articulating joints. Uncovering the underlying transport mechanisms is key to the understanding of the cross-talk between articular cartilage and subchondral bone. Here, we describe the mechanisms that facilitate transport at the osteochondral interface. Using scanning electron microscopy (SEM), we found a continuous transition of mineralization architecture from the non-calcified cartilage towards the calcified cartilage. This refurbishes the classical picture of the so-called tidemark; a well-defined discontinuity at the osteochondral interface. Using focused-ion-beam SEM (FIB-SEM) on one osteochondral plug derived from a human cadaveric knee, we elucidated that the pore structure gradually varies from the calcified cartilage towards the subchondral bone plate. We identified nano-pores with radius of 10.71 ± 6.45 nm in calcified cartilage to 39.1 ± 26.17 nm in the subchondral bone plate. The extracted pore sizes were used to construct 3D pore-scale numerical models to explore the effect of pore sizes and connectivity among different pores. Results indicated that connectivity of nano-pores in calcified cartilage is highly compromised compared to the subchondral bone plate. Flow simulations showed a permeability decrease by about 2000-fold and solute transport simulations using a tracer (iodixanol, 1.5 kDa with a free diffusivity of 2.5 × 10−10 m2/s) showed diffusivity decrease by a factor of 1.5. Taken together, architecture of the nano-pores and the complex mineralization pattern in the osteochondral interface considerably impacts the cross-talk between cartilage and bone.

Original languageEnglish
Article number110504
Number of pages8
JournalJournal of Biomechanics
Volume123
DOIs
Publication statusPublished - 2021

Keywords

  • Nanopore architecture
  • Osteochondral junction
  • Permeability
  • Pore -scale modelling
  • Solute transport

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