Movement of interstitial fluid in cortical bone is considered one of the important mechanisms affecting bone remodeling and fracture healing. To better understand such interstitial fluid movement, the hydrostatic permeability of cortical bone of the canine tibia was measured in this study.

It was found that age has significant influence on permeability. The cortical bone permeability of puppy tibiae is six times higher than that of adult tibiae. Adult tibial cortex is impermeable unless the superficial layer of the periosteal cortex is removed. The permeability differs between regions and locations of the tibia. The pathways for such extravascular interstitial fluid movement were also identified to be primarily the haversian and Volkmann's canals and secondarily the canalicular and lacunar spaces. The high permeability of their cortical bone may explain the increase in periosteal new bone formation seen in puppies when a venous tourniquet is applied.