Authors: Sarah H McBride Scott Dolejs Stefano Brianza Ulf Knothe Melissa L Knothe Tate
Publish Date: 2011/01/27
Volume: 39, Issue: 5, Pages: 1570-1581
Abstract
In an ovine femur model proliferative woven bone fills critically sized defects enveloped by periosteum within 2 weeks of treatment with the onestage bonetransport surgery We hypothesize that mechanical loading modulates this process Using highdefinition optical strain measurements we determined prevailing periosteal strains for normal and surgically treated ovine femora subjected ex vivo to compressive loads simulating in vivo stance shifting n = 3 per group normal vs treated We determined spatial distribution of calcein green a label for bone apposition in first the 2 weeks after surgery in 15° 30° and 45° sectors of histological cross sections through the middle of the defect zone n = 6 bones three to four sections per bone Finally we correlated early bone formation to either the maximal periosteal strain or the net change in maximal periosteal strain We found that treatment with the onestage bonetransport surgery profoundly changes the mechanical environment of cells within the periosteum during stance shift loading The pattern of early bone formation is repeatable within and between animals and relates significantly to the actual strain magnitude prevailing in the periosteum during stance shift loading Interestingly early bone apposition after the surgery correlates well to the maximal net change in strain above circa 2000–3000 με in tension or compression rather than strain magnitude per se providing further evidence that changes in cell shape may drive mechanoadaptation by progenitor cells These important insights regarding mechanobiological factors that enhance rapid bone generation in critically sized defects can be translated to the tissue and organ scale providing a basis for the development of best practices for clinical implementation and the definition of movement protocols to enhance the regenerative effectThis study was supported through a grant from the AO Foundation F0799K Sara McBride was supported through an NIH Training grant NIH/NIAMS T32 AR007505 In addition we would like to acknowledge Boyko GueorguievRüegg Chris Roberts and Dr Steven Sidik for their respective assistance with mechanical loading image analysis and statistics
Keywords: