Permeability of musculoskeletal tissues and scaffolding materials: experimental results and theoretical predictions

Fluid movement produces a wide range of phenomena in musculoskeletal tissues, including streaming potentials, hydrodynamic lubrication, nutrient transport, and mechanical signaling, all of which are governed by tissue permeability. Permeability is a measurement of the ease with which a fluid passes through a material and is described by Darcy's law. An appreciation of the flow-related structure-function relationships that have been found for musculoskeletal tissues as well as the materials used to engineer substitutes is important for clinicians and engineers alike. In addition, fluid transport phenomena is one of the most often neglected, but important, aspects of developing functional musculoskeletal tissue replacements. Mathematical models provide the means to relate permeability to microstructure and enable one to span multiple hierarchical length scales. In this article, we have summarized the experimentally determined permeability for a range of musculoskeletal tissues. In addition, we have included a summary of the microstructural models that are available to relate bulk permeability to microstructural flow profiles. These models have the potential to predict cellular level fluid shear stresses, nutrient and drug transport, degradation kinetics, and the fluid-solid interactions that govern mechanical response.