title: Strain gradients correlate with sites of periosteal bone formation.
abstract: We examined the hypothesis that peak magnitude strain gradients are spatially correlated with sites of bone formation. Ten adult male turkeys underwent functional isolation of the right radius and a subsequent 4-week exogenous loading regimen. Full field solutions of the engendered strains were obtained for each animal using animal-specific, orthotropic finite element models. Circumferential, radial, and longitudinal gradients of normal strain were calculated from these solutions. Site-specific bone formation within 24 equal angle pie sectors was determined by automated image analysis of microradiographs taken from the mid-diaphysis of the experimental radii. The loading regimen increased mean cortical area (+/-SE) by 32.3 +/- 10.5% (p = 0.01). Across animals, some periosteal bone formation was observed in every sector. The amount of periosteal new bone area contained within each sector was not uniform. Circumferential strain gradients (r2 = 0.36) were most strongly correlated with the observed periosteal bone formation. SED (a scalar measure of stress/strain magnitude with minimal relation to fluid flow) was poorly correlated with periosteal bone formation (r2 = 0.01). The combination of circumferential, radial, and longitudinal strain gradients accounted for over 60% of the periosteal new bone area (r2 = 0.63). These data indicate that strain gradients, which are readily determined given a knowledge of the bone's strain environment and geometry, may be used to predict specific locations of new bone formation stimulated by mechanical loading.
authors.affiliation: Department of Orthopaedics, State University of New York at Stony Brook, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Gross
authors.forename: J L
authors.initials: JL
authors.lastname: Edwards
authors.forename: K J
authors.initials: KJ
authors.lastname: McLeod
authors.forename: C T
authors.initials: CT
authors.lastname: Rubin
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D016723:Bone Remodeling / Q000502:physiology; D008297:Male; D008954:Models, Biological; D010012:Osteogenesis / Q000502:physiology*; D010521:Periosteum / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D013314:Stress, Mechanical; D014422:Turkeys