RESUMO
Mechanical stimuli play a significant role in the process of long bone development as evidenced by clinical observations and in vivo studies. Up to now approaches to understand stimuli characteristics have been limited to the first stages of epiphyseal development. Furthermore, growth plate mechanical behavior has not been widely studied. In order to better understand mechanical influences on bone growth, we used Carter and Wong biomechanical approximation to analyze growth plate mechanical behavior, and explore stress patterns for different morphological stages of the growth plate. To the best of our knowledge this work is the first attempt to study stress distribution on growth plate during different possible stages of bone development, from gestation to adolescence. Stress distribution analysis on the epiphysis and growth plate was performed using axisymmetric (3D) finite element analysis in a simplified generic epiphyseal geometry using a linear elastic model as the first approximation. We took into account different growth plate locations, morphologies and widths, as well as different epiphyseal developmental stages. We found stress distribution during bone development established osteogenic index patterns that seem to influence locally epiphyseal structures growth and coincide with growth plate histological arrangement.
Assuntos
Desenvolvimento Ósseo/fisiologia , Simulação por Computador , Lâmina de Crescimento/crescimento & desenvolvimento , Lâmina de Crescimento/fisiologia , Adolescente , Criança , Pré-Escolar , Epífises/embriologia , Epífises/crescimento & desenvolvimento , Epífises/fisiologia , Feminino , Análise de Elementos Finitos , Lâmina de Crescimento/embriologia , Humanos , Lactente , Recém-Nascido , Modelos Lineares , Masculino , Modelos Biológicos , Osteogênese/fisiologia , Gravidez , Estresse MecânicoRESUMO
PURPOSE: This study was conducted to verify the predictive value of epiphyseal ossification center measurements in estimating gestational age. METHODS: Women with singleton pregnancies of 30-40 weeks gestation (n = 377) were enrolled in this prospective study. The distal femoral, proximal tibial, and proximal humeral ossification centers were identified and measured. A nomogram of fetal bone development was created using the sum of the three diameters. RESULTS: Gestational age correlated well with the diameters of the distal femoral and the proximal tibial epiphyseal ossification centers but even better with the sum of the three ossification centers. Positive predictive values of the fetus having gestational age of at least 37 weeks when the sum of the three centers was 7, 11, and 13 mm were 82%, 94%, and 100%, respectively. A nomogram was created using the sum of the ossification centers for 30-40 weeks' gestational age. CONCLUSIONS: Ultrasonographic visualization of the epiphyses ossification centers may be a useful marker of fetal gestational age.
Assuntos
Epífises/diagnóstico por imagem , Fêmur/embriologia , Idade Gestacional , Úmero/embriologia , Tíbia/embriologia , Adolescente , Adulto , Epífises/embriologia , Epífises/fisiologia , Feminino , Desenvolvimento Fetal , Humanos , Osteogênese , Gravidez , Terceiro Trimestre da Gravidez , Estudos Prospectivos , Ultrassonografia Pré-NatalRESUMO
BACKGROUND: Histologic delineation of the events involved in the development of long bones and the developmental age at which these events occur is needed to elucidate the genetic and molecular mechanisms associated with these events. This report describes the sequence of histologic events involved in the formation of long bones and their epiphyses in the New Zealand White rabbit. METHODS: Prenatal studies were performed on twelve, fourteen, fifteen, sixteen, eighteen, twenty-one, twenty-four, and twenty-seven-day-old rabbit embryos, and postnatal studies were performed on newborn rabbits and on three-to-four-day-old; one, two, four, and six-week-old; and two, three, four, six, and eight-month-old rabbits. Histologic specimens from embryos were embedded in plastic and stained with toluidine blue or safranin O-fast green, and specimens from postnatal rabbits were embedded in paraffin and stained with hematoxylin and eosin or safranin O-fast green. RESULTS: Studies of twelve-day-old embryos demonstrated upper and lower limb buds filled with undifferentiated mesenchymal cells, and studies of fourteen-day-old embryos showed mesenchymal condensation and beginning cartilage formation outlining major long bones. Long-bone and epiphyseal development progressed through sixteen structural stages, and the developmental age at which these stages occurred was determined. These stages included limb-bud formation with uniform distribution of mesenchymal cells and formation of an apical ectodermal ridge (stage 1); mesenchymal condensation (stage 2); cartilage differentiation (stage 3); formation of a primary center of ossification (stage 4a); epiphyseal cartilage vascularization with formation of cartilage canals (stage 7); vascular invasion of the developing secondary ossification center (stage 9); bone formation and marrow cavitation in the secondary ossification center with formation of hematopoietic marrow (stage 10); fullest relative extent of secondary-ossification-center development in epiphyseal cartilage (stage 14); thinning of the physis (stage 15); and resorption of the physis with establishment of continuity between epiphyseal and metaphyseal circulations (stage 16).
Assuntos
Desenvolvimento Ósseo/fisiologia , Osso e Ossos/embriologia , Epífises/embriologia , Epífises/crescimento & desenvolvimento , Animais , Animais Recém-Nascidos , Cartilagem/crescimento & desenvolvimento , Embrião de Mamíferos , Feto , Idade Gestacional , Osteogênese/fisiologia , CoelhosRESUMO
Foram analisadas 1000 ultrassonografias de rotina realizadas em gestantes normais, no período de janeiro a novembro de 1990. O núcleo de ossificaçäo epifisária fetal proximal do úmero apareceu de forma significante após a 38§ semana (p < 0,001), constituindo-se em recurso auxiliar valioso na avaliaçäo da idade gestacional no 3ª trimestre).
Assuntos
Humanos , Feminino , Gravidez , Desenvolvimento Ósseo/fisiologia , Epífises , Epífises/embriologia , Úmero/embriologia , Úmero , Idade GestacionalRESUMO
A época de aparecimento do núcleo fetal de ossificaçäo epifisiária distal do fêmur e sua variaçäo sexual foi avaliada através da análise de uma amostra de 659 casos. As gestantes encontravam-se entre a 28ª e a 40ª semanas, näo apresentando intercorrências clínicas ou obstétricas e foram seguidas entre janeiro e novembro de 1990. Todas as gestaçöes eram únicas e sem malformaçöes fetais. O núcleo distal do fêmur surgiu de forma significante entre a 31ª e a 33ª semanas. Para o sexo feminino, sua ocorrência foi entre a 31ª e a 33ª semanas; no masculino, apareceu entre a 32ª e a 33ª semanas (P < 0,001). Embora os resultados sugiram uma tendência do núcleo distal do fêmur dos fetos femininos preceder o dos fetos masculinos, näo houve significância estatística na diferença sexual observada.
Assuntos
Humanos , Masculino , Feminino , Gravidez , Desenvolvimento Ósseo , Epífises/embriologia , Fêmur/embriologia , Desenvolvimento Fetal , Sexo , Idade Gestacional , Fatores Sexuais , Fatores de Tempo , Ultrassonografia Pré-NatalRESUMO
The time of sonographic appearance of the proximal tibial epiphyseal ossification center and its sexual variation was assessed in 659 normal pregnancies. Proximal tibial center appears between 34-37 weeks gestation. In female fetuses, it appears between 34-35 weeks and in males, between 35-36 weeks (P < 0.001). There was a tendency of female proximal tibial center appearance to precede male appearance, by approximately one week. This difference, however, didn't show statistical significance.