Periosteum Permeability Exhibits Mechanically Responsive and Direction Dependent Behavior

INTRODUCTION The periosteum serves as a stabilizing boundary membrane to the bone it envelops and is known to contain pluripotent and osteochodroprogenitor cells. Periosteal cells have been shown to have the capacity to infill critical sized defects with proliferative woven bone within weeks of injury [1,2]. Critical sized defect healing has been shown to be maximal when cells egress from periosteum left in situ around critical sized defects [1], followed by cells egressing from periosteal transplants, or periosteum derived cells seeded on a collagen membrane, when encased by a flow directing periosteal replacement implant [3]. Recently, the material properties of the periosteum have been characterized providing information valuable to understanding the environment of the pluripotent and osteochondroprogenitor cells within the tissue [4]. Yet to date, the permeability characteristics of periosteum remain relatively unexplored, which provided the impetus for our study. Namely, we aim to measure permeability of fresh ovine femoral periosteum. We hypothesize that periosteal permeability depends on the volumetric flow rate applied across the tissue. Furthermore, we hypothesize that the permeability is anisotropic with respect to the direction of flow.