title: Growth plate cartilage shows different strain patterns in response to static versus dynamic mechanical modulation.
abstract: Longitudinal growth of long bones and vertebrae occurs in growth plate cartilage. This process is partly regulated by mechanical forces, which are one of the underlying reasons for progression of growth deformities such as idiopathic adolescent scoliosis and early-onset scoliosis. This concept of mechanical modulation of bone growth is also exploited in the development of fusionless treatments of these deformities. However, the optimal loading condition for the mechanical modulation of growth plate remains to be identified. The objective of this study was to evaluate the effects of in vitro static versus dynamic modulation and of dynamic loading parameters, such as frequency and amplitude, on the mechanical responses and histomorphology of growth plate explants. Growth plate explants from distal ulnae of 4-week-old swines were extracted and randomly distributed among six experimental groups: baseline ([Formula: see text]), control ([Formula: see text]), static ([Formula: see text]) and dynamic ([Formula: see text]). For static and dynamic groups, mechanical modulation was performed in vitro using an Indexed CartiGen bioreactor. A stress relaxation test combined with confocal microscopy and digital image correlation was used to characterize the mechanical responses of each explant in terms of peak stress, equilibrium stress, equilibrium modulus of elasticity and strain pattern. Histomorphometrical measurements were performed on toluidine blue tissue sections using a semi-automatic custom-developed MATLAB toolbox. Results suggest that compared to dynamic modulation, static modulation changes the strain pattern of the tissue and thus is more detrimental for tissue biomechanics, while the histomorphological parameters are not affected by mechanical modulation. Also, under dynamic modulation, changing the frequency or amplitude does not affect the biomechanical response of the tissue. Results of this study will be useful in finding optimal and non-damaging parameters for the mechanical modulation of growth plate in fusionless treatments.
authors.affiliation: Department of Mechanical Engineering, Ecole Polytechnique de Montreal, P.O. Box 6079, Station Centre-Ville, Montreal, QC, H3C 3A7, Canada.|Sainte-Justine University Hospital Center, Montreal, QC, Canada.
authors.forename: Rosa
authors.initials: R
authors.lastname: Kaviani
authors.affiliation: Sainte-Justine University Hospital Center, Montreal, QC, Canada.
authors.forename: Irene
authors.initials: I
authors.lastname: Londono
authors.affiliation: Sainte-Justine University Hospital Center, Montreal, QC, Canada.|Department of Surgery, University of Montreal, Montreal, QC, Canada.
authors.forename: Stefan
authors.initials: S
authors.lastname: Parent
authors.affiliation: Sainte-Justine University Hospital Center, Montreal, QC, Canada.|Faculty of Dental Medicine, University of Montreal, Montreal, QC, Canada.
authors.forename: Florina
authors.initials: F
authors.lastname: Moldovan
authors.affiliation: Department of Mechanical Engineering, Ecole Polytechnique de Montreal, P.O. Box 6079, Station Centre-Ville, Montreal, QC, H3C 3A7, Canada. isabelle.Villemure@polymtl.ca.|Sainte-Justine University Hospital Center, Montreal, QC, Canada. isabelle.Villemure@polymtl.ca.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Villemure
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002356:Cartilage / Q000502:physiology*; D049109:Cell Proliferation; D004548:Elasticity; D006132:Growth Plate / Q000473:pathology / Q000502:physiology*; D006984:Hypertrophy; D013194:Staining and Labeling; D013314:Stress, Mechanical; D013552:Swine
keywords: Digital image correlation; Dynamic modulation; Growth plate; Histomorphometry; Mechanical characterization; Mechanical modulation; Static modulation