The effect of exogenous somatotropin (eST) on bone changes were evaluated in twenty-nine juvenile horses in race training using radiographs of the third metacarpal obtained over the course of a 128 day research project. A biodensitometer was used to measure bone density, and a micrometer was used to measure cortical bone width and medullary cavity width. Fifteen horses were given daily intramuscular injections of eST and fourteen horses were given daily intramuscular injections of sterile saline and served as the control group. By day 128, the increase in total radiographic bone aluminum equivalence (RBAE) was significantly greater in the eST horses than in the control horses. The increases in RBAE in the dorsal and the medial cortices were greater in the eST horses than in the control horses, but these differences were not significant. There was a trend for changes in the ratio of RBAE in the dorsal to palmar and in the medial to lateral cortices to be greater in the eST than in the control horses. By day 128, the increases in both the dorsal and the medial cortical bone width were significantly greater in the eST than in the control group of horses. The eST horses had a significantly greater decrease in dorsal to palmar medullary cavity width, and increase in dorsal to palmar bone diameter than the control group. A computed index of dorsal cortical bone increased significantly more in the eST than in the control group. The stresses applied to bone are greater in the dorso-medial direction in racehorses. To decrease the strain, bone must either increase in bone mineral density, cortical width, and/or bone diameter. Both the eST group and the control group did make these changes in bone over time, but the eST group more effectively remodeled and modeled bone to increase the strength of the third metacarpal than did the control group of horses. In this research project, exogenous somatotropin treatment had a positive effect on the density and geometry of the third metacarpal. These changes are believed to result in a decreased risk of bone injury to the eST treated horses.

<p>Validerat; 20101217 (root)</p>

Stress fractures are common in the limb bones of human and equine athletes alike. Repetitive skeletal loading can lead to remodeling and the accumulation of microdamage in bone, which only becomes grossly evident during catastrophic fracture of the bone due to the accumulated microdamage. Though various metrics attempting to quantify bone health exist, none have distinguished themselves as early predictors of the susceptibility of bone to fracture. In this exploratory study, we examine the ability of several evaluation methods to distinguish between third metacarpal (MC3) bones from racehorses that have experienced a limb-bone fracture and from those that have not. Third metacarpal bones were harvested from deceased Thoroughbred racehorses and categorized into four groups: MC3 bones from horses whose cause of death was not related to skeletal fracture (Control group, n = 20), MC3 bones form horses that were euthanized after fracturing proximal sesamoid bones (Sesamoid group, n = 20), MC3 bones from horses that were euthanized after fracturing a non-MC3 long bone (Long Bone group, n = 19), and MC3 bones from horses that were euthanized after fracturing an MC3 (MC3 group, n = 5). Each MC3 bone underwent testing using a variety of tools and methods at the proximal, midshaft, and distal levels of the lateral, dorsal, and medial surfaces. All tools and methods (OsteoProbe reference point indentation, BioDent reference point indentation, x-ray, micro-CT, and pQCT) exhibited some capability in differentiating between control and fracture groups. The long-term objective of this project is to create a model that will utilize data from a set of evaluations and output the susceptibility of the horse to fracture a bone, a long bone, or the MC3, specifically. Although the sample size in this study is not sufficient to create a reliably predictive logistic regression model, promising results from preliminary models provide incentive to further explore the possibility of creating one. While clinical practicality will be a vital consideration for a model in the future, establishing this basis for the capability of each evaluation at hand is a necessary first step in predicting and preventing fracture in bone.

Le remodelage osseux est un processus qui permet le renouvellement du tissu osseux tout au long de la vie des individus (Toppets et al. 2004). Il est bien connu que le remodelage est influencé à la fois par l’environnement mécanique (charges, activités) et par les besoins métaboliques (Pearson et Lieberman 2004; Rosas et Martinez-Maza 2010). Cependant, les effets des charges mécaniques sur le remodelage osseux restent encore peu compris (Lad and al. 2016; Pfeiffer and al 2006). Cette étude a pour but d’évaluer les réponses microscopiques des os aux charges mécaniques. L’échantillon étudié correspond à des paires de seconds métacarpes, issues de deux populations d’origine géographique distinctes (n=103, 55 Euro-Canadiens et 48 Inuits). À partir de section en coupe provenant de la mi-diaphyse, les lames minces ont été analysées selon quatre quadrants anatomiques : antérieur, médial, postérieur et latéral. Afin de contrôler les facteurs non mécaniques qui influencent le remodelage (tels l’âge) l’asymétrie entre les paires des métacarpes est calculée pour toutes les variables étudiées. Les charges sont estimées par les valeurs d’asymétrie de trois variables biomécaniques macroscopiques : Imax, Imin et J. Les asymétries de la densité de population des ostéons (OPD), de l’aire moyenne des ostéons et des canaux de Havers furent calculées pour estimer la réponse osseuse microscopique. De plus, il fut testé l’effet de la densité de population des ostéons sur leur aire moyenne. Les résultats démontrent que la densité d’ostéons diminue pour certains groupes (chez les hommes de St Thomas, r = - 0,412 et les femmes Inuits r = -0,547), et que les aires moyennes des ostéons et des canaux de Havers augmentent dans le quadrant antérieur du métacarpe le plus chargé (chez St-Thomas r = 0,297). De plus, il existe une relation négative entre l’augmentation de la densité d’ostéons et leur aire moyenne, dans le quadrant postérieur des femmes de St Thomas (r = -0,496). En conclusion, les charges mécaniques ont un impact sur la microstructure de l’os, rendant possible l’étude des charges à travers l’analyse histomorphologique du tissu osseux. / Bone remodeling is the process by which the skeleton can be renewed throughout the life of individuals (Toppets and al. 2004). It is well known that bone remodeling is a function of both mechanical (loads, activities) and non-mechanical factors such as metabolic needs of the bone (Pierson and Lieberman 2004; Rosas and Martinez-Maza 2010). However, the effects of mechanical environment on bone remodeling still remain poorly understood (Lad and al. 2016; Pfeiffer and al. 2006). This study aims to evaluate the microscopic bone responses to mechanical loading. The sample analyzed represents pairs of second metacarpal from two genetically separated populations (n=103, 55 Euro-Canadiens and 48 Inuits). From mid-shaft sections, thin sections were analyzed using four anatomical quadrants: anterior, medial, posterior and lateral. In order to control the influence of non-mechanical factors on bone remodeling, the asymmetry between pairs of metacarpals is calculated for each variable studied. Mechanical loading is estimated from the asymmetry values of three macroscopic biomechanical variables: Imax, Imin and J. Besides, asymmetries of osteon population density (OPD), mean areas of osteons and Havers canals were measured to estimate the microscopic bone response. Furthermore, it was tested the effect of osteon population density on osteon area. Results show that osteon population density decreases in some groups (in St-Thomas men r = - 0,412 and Inuit women r = -0,547), and the mean area of osteon and Havers canals increase in the more loaded side (in St-Thomas r = 0,297). In addition, there is a negative relationship between increased density of osteons and their mean areas in the posterior quadrant in St-Thomas women (r = -0,496). In conclusion, mechanical loading seems to have an impact on bone microstructure, making possible the inference of mechanical loadings through the study of bone histomorphology.

Cette étude teste l’hypothèse que le remodelage osseux dans le deuxième métacarpe peut être utilisé pour estimer l’âge à la mort. Les métacarpes utilisés dans cette analyse proviennent d’un cimetière d’Ontario, incluant des individus d’origine européenne (n=63; 34 hommes; 29 femmes). Leur âge varie de 19 à 61 ans (moyenne: 41,1±11,6). L’âge était connu ou a été estimé indépendamment à partir de la morphologie générale du squelette. À partir de lames minces coupées à la mi-diaphyse, la densité de population des ostéons (OPD; ostéons/mm2 intacts et fragmentaires) a été calculée pour huit colonnes du périoste à l’endoste, deux par quadrant anatomique. Les régressions par calibration classique ont produit une série d’équation pour les estimations de l’âge pour chaque sexe, sexes combinés, et en fonction de la latéralité. La méthode utilisée diminue l’efficacité des estimations mais elle a l’avantage de réduire les biais. Quand les sexes sont combinés, l’OPD est corrélé modérément mais significativement avec l’âge (droit r2= 0,35; gauche r2=0,28). Cependant, quand les hommes et les femmes sont analysés séparément, la corrélation entre l’OPD et l’âge dans l’échantillon féminin est meilleure (droit r2=0,48; gauche r2=0,39) alors que celle des hommes est réduite (droit r2=0,29; gauche r2=0,22). Ce résultat a déjà été observé dans d’autres études, mais n’est pas expliqué. Les résultats démontrent aussi une meilleure corrélation entre l’OPD et l’âge du côté droit que du côté gauche. Tous les résultats présentés ici supportent l’hypothèse que l’OPD du métacarpe est corrélé avec l’âge effectif (c’est-à-dire connu ou estimé), les régressions de l’OPD sur l’âge (droit-gauche combinés ou séparés, sexes combinés ou séparés) étant toutes significatives. / This preliminary study tests the hypothesis that evidence of bone remodeling in the second metacarpal can be used to estimate age at death. The metacarpals used in this analysis originated from an historic European sample from Ontario, Canada (n=63, 34 males and 29 females). They range in age from 19 to 61 years (mean=41.1±11.6). Age was known or independently estimated from gross morphology. For each right and left second metacarpal, Osteon Population Density (OPD; intact and fragmentary osteons/mm2) was recorded on four quadrants (anterior, posterior, medial, lateral), sampling two periosteal to endosteal columns separated by one column width. Classical calibration analysis produced a series of equations for estimates of age for each sex, sexes combined, and according to laterality. The method reduces the efficiency of estimates but has the advantage of reducing bias. When the sexes were combined, OPD correlated moderately but significantly with age (right r2=0.35, left r2= 0.28). However, when males and females were analyzed separately, the correlation between OPD and age in the female sample was improved (right r2=0.48, left r2=0.39) while the correlation in males was reduced (right r2=0.29, left r2=0.22). It remains unclear why the correlation is better in females than males, but similar results have been obtained in other studies. These results also indicate that there is a better correlation between OPD and age in the right second metacarpal than in the left. The results presented here support the hypothesis that the OPD of the metacarpal is correlated with chronological age (known or estimated) as all regressions of the OPD on age (right-left combined and separate, sexes combined and separated) are significant.

A fundamentação de métodos diagnósticos precoces na ortopedia de eqüinos é de extrema importância clínica, cirúrgica e econômica. O presente estudo teve como objetivo estudar a correlação da densidade mineral óssea do terceiro metacarpiano de eqüinos, obtida pelo método de absorciometria radiográfica, com a resistência dos mesmos quando submetidos a ensaios biomecânicos de compressão e flexão. Utilizaram-se trinta pares de osso terceiro metacarpiano de eqüinos adultos, os quais foram dissecados, radiografados, analisados pelo método de absorciometria radiográfica, submetidos ao estudo tomográfico e a ensaios biomecânicos. Através dos dados obtidos não se observou correlação significativa entre os valores de densidade óptica radiográfica e as propriedades biomecânicas do osso terceiro metacarpiano. Concluiu-se que não se pode inferir que os valores de densidade óssea obtidos pela absorciometria radiográfica do osso terceiro metacarpiano de um eqüino tenha correlação com a capacidade deste osso de absorver cargas de compressão e flexão. / The complete knowledge about non-invasive methods for early disgnostics in equine orthopedy is economicaly important. This experiment has studied the correlation between bone mineral density determined by radiographic absorptiometry and bone resistance of equine third metacarpal bone submitted to both compression and flexion testings. Thirty pairs of third metacarpal bone of adult horses were collected, dissected, radiographed, analysed by the radiographic absorptiometry technique, and submitted to tomographic study and biomechanical testings. The results have shown there is no significant correlation between radiographic bone density values and biomechanical properties of the third metacarpal bone. Therefore, it has been concluded bone mineral density of the third metacarpal bone determined by radiographic absorptiometry do not predict bone capacity to resist compression and flexion loads.

Cette étude teste l’hypothèse que le remodelage osseux dans le deuxième métacarpe peut être utilisé pour estimer l’âge à la mort. Les métacarpes utilisés dans cette analyse proviennent d’un cimetière d’Ontario, incluant des individus d’origine européenne (n=63; 34 hommes; 29 femmes). Leur âge varie de 19 à 61 ans (moyenne: 41,1±11,6). L’âge était connu ou a été estimé indépendamment à partir de la morphologie générale du squelette. À partir de lames minces coupées à la mi-diaphyse, la densité de population des ostéons (OPD; ostéons/mm2 intacts et fragmentaires) a été calculée pour huit colonnes du périoste à l’endoste, deux par quadrant anatomique. Les régressions par calibration classique ont produit une série d’équation pour les estimations de l’âge pour chaque sexe, sexes combinés, et en fonction de la latéralité. La méthode utilisée diminue l’efficacité des estimations mais elle a l’avantage de réduire les biais. Quand les sexes sont combinés, l’OPD est corrélé modérément mais significativement avec l’âge (droit r2= 0,35; gauche r2=0,28). Cependant, quand les hommes et les femmes sont analysés séparément, la corrélation entre l’OPD et l’âge dans l’échantillon féminin est meilleure (droit r2=0,48; gauche r2=0,39) alors que celle des hommes est réduite (droit r2=0,29; gauche r2=0,22). Ce résultat a déjà été observé dans d’autres études, mais n’est pas expliqué. Les résultats démontrent aussi une meilleure corrélation entre l’OPD et l’âge du côté droit que du côté gauche. Tous les résultats présentés ici supportent l’hypothèse que l’OPD du métacarpe est corrélé avec l’âge effectif (c’est-à-dire connu ou estimé), les régressions de l’OPD sur l’âge (droit-gauche combinés ou séparés, sexes combinés ou séparés) étant toutes significatives. / This preliminary study tests the hypothesis that evidence of bone remodeling in the second metacarpal can be used to estimate age at death. The metacarpals used in this analysis originated from an historic European sample from Ontario, Canada (n=63, 34 males and 29 females). They range in age from 19 to 61 years (mean=41.1±11.6). Age was known or independently estimated from gross morphology. For each right and left second metacarpal, Osteon Population Density (OPD; intact and fragmentary osteons/mm2) was recorded on four quadrants (anterior, posterior, medial, lateral), sampling two periosteal to endosteal columns separated by one column width. Classical calibration analysis produced a series of equations for estimates of age for each sex, sexes combined, and according to laterality. The method reduces the efficiency of estimates but has the advantage of reducing bias. When the sexes were combined, OPD correlated moderately but significantly with age (right r2=0.35, left r2= 0.28). However, when males and females were analyzed separately, the correlation between OPD and age in the female sample was improved (right r2=0.48, left r2=0.39) while the correlation in males was reduced (right r2=0.29, left r2=0.22). It remains unclear why the correlation is better in females than males, but similar results have been obtained in other studies. These results also indicate that there is a better correlation between OPD and age in the right second metacarpal than in the left. The results presented here support the hypothesis that the OPD of the metacarpal is correlated with chronological age (known or estimated) as all regressions of the OPD on age (right-left combined and separate, sexes combined and separated) are significant.

A fundamentação de métodos diagnósticos precoces na ortopedia de eqüinos é de extrema importância clínica, cirúrgica e econômica. O presente estudo teve como objetivo estudar a correlação da densidade mineral óssea do terceiro metacarpiano de eqüinos, obtida pelo método de absorciometria radiográfica, com a resistência dos mesmos quando submetidos a ensaios biomecânicos de compressão e flexão. Utilizaram-se trinta pares de osso terceiro metacarpiano de eqüinos adultos, os quais foram dissecados, radiografados, analisados pelo método de absorciometria radiográfica, submetidos ao estudo tomográfico e a ensaios biomecânicos. Através dos dados obtidos não se observou correlação significativa entre os valores de densidade óptica radiográfica e as propriedades biomecânicas do osso terceiro metacarpiano. Concluiu-se que não se pode inferir que os valores de densidade óssea obtidos pela absorciometria radiográfica do osso terceiro metacarpiano de um eqüino tenha correlação com a capacidade deste osso de absorver cargas de compressão e flexão. / The complete knowledge about non-invasive methods for early disgnostics in equine orthopedy is economicaly important. This experiment has studied the correlation between bone mineral density determined by radiographic absorptiometry and bone resistance of equine third metacarpal bone submitted to both compression and flexion testings. Thirty pairs of third metacarpal bone of adult horses were collected, dissected, radiographed, analysed by the radiographic absorptiometry technique, and submitted to tomographic study and biomechanical testings. The results have shown there is no significant correlation between radiographic bone density values and biomechanical properties of the third metacarpal bone. Therefore, it has been concluded bone mineral density of the third metacarpal bone determined by radiographic absorptiometry do not predict bone capacity to resist compression and flexion loads.

Ce travail de thèse concerne l'articulation trapézométacarpienne. La première partie du travail a concerné l'étude de la morphogénèse de l'arche palmaire par modélisation géométrique 3D. Cinq embryons ont été utilisés. Les résultats de cette étude montre le caractère asymétrique et l'opposition précoce du pouce chez l'embryon humain. La deuxième partie a consisté à partir d'un protocole IRM spécifique sur 5 sujets sains à déterminer la cinématique 3D de l'articulation trapézo-métacarpienne en utilisant les axes hélicoïdaux. La troisième partie, suivant le même protocole sur sujets pathologiques à partir d'image scanner a permis d'évaluer l'effet des différents types de traitement en cas de rhizarthrose. Les résultats trouvent leur application dans l'évaluation quantitative des pathologies de l'articulation trapézo-métacarpienne ainsi que dans le développement des prothèses. / This work concerned the first carpo-metacarpal joint. The first part of this work was the study of the morphogenesis of the palmar arch using three-dimensional geometrie modeling. Five embryos were used for this study. The results of this study support the hypothesis that opposition and asymmetry of the thumb appears early in embryological development. In the second part, with specifie MRI protocol on 5 normal subjects, the objective was to quantify the 3D motion of the trapezo-metacarpal joint using helical axes theory. In the last part, using the same protocol on pathological subjects (CT scan images), the objective was to evaluate the effect of different type of treatment of the first carpo­ metacarpal arthritis.The results of the work are of interest for the quantitative evaluation of pathological trapezo-metacarpal joint and in the development of prosthesis.

No description available.