The Short and Long Term Effects of in Vivo Cyclic Axial Compression Applied During Puberty on Bone Growth, Morphometry and Biomechanics
Year: 2019
Type: dissertation
Abstract: RESUME
Pendant la croissance rapide pubertaire, les os sont sensibles aux stimuli mecaniques environnants. Les sollicitations mecaniques telles que les activites physiques frequentes peuvent contribuer positivement au developpement du squelette. Ces activites peuvent entrainer de faibles impacts (comme la marche, la natation, etc.) ou des impacts eleves (comme la course, le saut, etc.) selon la nature de l'activite physique. En plus de la charge mecanique, les facteurs nutritionnels contribuent egalement de maniere significative au developpement osseux pendant les periodes de croissance. Les effets des charges d'impact sur la croissance et le developpement osseux au cours de l'adolescence ont ete investigues par plusieurs chercheurs dans des etudes animales et cliniques, mais les resultats sont variables. Les recherches anterieures n'ont pas clairement aborde les effets isoles du chargement d'impact par rapport aux facteurs nutritionnels lors de l'evaluation de la croissance et du developpement osseux. De plus, on ne sait toujours pas si les effets induits par les charges mecaniques pendant l'adolescence persistent a l'âge adulte et influencent les proprietes structurelles osseuses a long terme.
L'objectif de cette these etait d'evaluer in vivo les effets des charges cycliques en compression faibles, moyennes et elevees appliquees pendant la puberte sur la croissance osseuse (a maturite squelettique) ainsi que sur la qualite osseuse et la resistance mecanique (a l'âge adulte) en utilisant un modele animal (tibia de rat). Cet objectif a ete atteint en completant quatre etudes complementaires. Tout d'abord, une dose d’exposition aux rayons X a haute resolution mais securitaire a ete determinee pour l'imagerie in vivo repetee par micro-CT des tibias de rat en croissance qui n'affecterait pas la croissance ou la microstructure osseuses. Deuxiemement, relation contraintes-deplacements a ete etablie pour les tibias pendant la periode de croissance pubertaire du rat. Un outil de modelisation informatique a egalement ete mis au point et valide pour evaluer les contraintes de l’os sous compression. Troisiemement, les effets de trois niveaux de charges cycliques en compression a la puberte sur la croissance osseuse, la morphometrie et la biomecanique ont ete evalues a maturite du squelette. Enfin, les effets de ces trois niveaux de charges cycliques en compression appliquees a la puberte sur la microstructure osseuse ont ete evalues a la maturite du squelette et apres pres d'un an d'entrainement a l'âge adulte.
Dans la premiere etude, trois doses de rayonnement micro-CT de 0,83, 1,65 et 2,47 Gy ont ete testees.----------ABSTRACT
During the adolescent period, rapidly growing bones react sensitively to induced mechanical stimuli. Mechanical loadings such as daily physical activities can positively contribute to skeletal development. They can range from low impact activities (such as walking, swimming, etc.) to high impact activities (such as running, jumping, etc.) depending on the nature of the physical activity. Along with mechanical loading, nutritional factors also significantly contribute to bone development during growth periods. The effects of impact loadings on bone growth and development during the adolescent period have been investigated by several researchers in animal and clinical studies, but results are inconsistent. Previous research has not clearly addressed the isolated effects of impact loading from nutritional factors while evaluating bone growth and development. Moreover, it is still unclear whether the effects induced by mechanical loading during adolescence remains in adulthood and influence bone structural properties in the long term.
The objective of this thesis was to evaluate the effects of in vivo low, medium, and high cyclic axial compression applied during puberty on bone growth (at skeletal maturity) as well as on bone quality and mechanical strength (at adulthood) using an animal (rat tibia) model. This objective was achieved by conducting four interconnected studies. First, a safe yet high-resolution effective radiation dose was determined for repeated in vivo micro-CT scanning of the growing rat tibiae, which would not affect bone growth or microstructure. Secondly, rat tibial displacements vs strains relationships were established for the adolescent growing period via a strain calibration study. A computational modeling tool was also developed and validated for assessing bone strains under compressive loading. Thirdly, the effects of three different cyclic axial compression during puberty on bone growth, morphometry and biomechanics were assessed at skeletal maturity. Finally, the effects of three different cyclic axial compression during puberty on bone microstructure were assessed both at skeletal maturity and after almost a year of detraining period at adulthood.
In the first study, three micro-CT radiation doses of 0.83, 1.65 and 2.47 Gy were tested. The right tibiae of male Sprague-Dawley rats were scanned using an in vivo micro-CT scanning protocol from their 4th to 12th week of age with these radiation doses. The left tibiae were used as control. The left tibiae were only scanned on the last day, before sacrifice. Bone marrow cells were investigated, bone growth rates and histomorphometric analyses were performed, and bone structural parameters were determined for both left and right tibiae.
Author: Tanvir Mustafy
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2999747975