ABSTRACT
La placa de crecimiento es una estructura que está conformada por células, denominadas condrocitos, que se ordenan en columnas y confieren el alargamiento del hueso debido a su proliferación e hipertrofia. En cada columna se pueden observar condrocitos en estado proliferativo (que se dividen constantemente), e hipertrófico (que crecen para obtener una forma casi esférica). Estas células expresan diferentes proteínas y moléculas a lo largo de su vida media y tienen un comportamiento especial que puede depender de su entorno local mecánico y bioquímico. En este artículo se desarrolla un modelo matemático que describe la relación entre la geometría, el crecimiento por proliferación e hipertrofia y la invasión vascular con los factores bioquímicos y mecánicos presentes durante el desarrollo endocondral
The growth plate is a structure composed of cells called chondrocytes arranged in columns and causing the bone lengthening due to its proliferation and hypertrophy. In each column it may observed the presence of chondrocytes in proliferation stage (constantly divided) and hypertrophy stage (growing to obtain a almost spherical shape). These cells express different proteins and molecules during half-life and have a special behavior that may to depend on its mechanical or biochemical local environment. In present paper it is developed a mathematical model describing the relationship among the geometry, proliferation and hypertrophy growth and the vascular invasion by biochemical and mechanical factors present during the endochondral development
ABSTRACT
We investigated the effect of tibial lengthening by means of callotasis on enchondral growth of the tibia, Ninety-nine 5-week-old immature rabbits were separated into five groups according to the percentage of lengthening : GroupI(10% lengthening), Group II (20% lengthening), Group III (30% lengthening), Group IV (40% lengthening), Group V (sham operation without lengthening). Osteotomy of the tibia and fibula was made at the proximal metaphysiodiaphyseal junction. Distraction was started at the rate of 0.25mm twice a day from the third postoperative day to simulate the currently accepted callotasis. In Group I, II, and V, there two were no statistically significant differences in the growth rates between the left operated and the right normal tibiae. In contrast, the ratios of left over right tibial length decreased significantly in Group III (4.8%), and Group IV (8.6%) at the completion of lengthening(p < 0.0001), and remained decreased until near skeletal maturity. Histomorphometric study revealed that, in Group III and IV, there were statistically significant decreases in the ratios of the thickness of left over night tibiae at both proximal and distal growth plate(p < 0.0001). Immunohistochemical study also revealed that, in Group III and Group IV, the ratios of left over right bromodeoxyuridine(BrdUrd) labeling percentage decreased significantly (p < 0.0001). In summary, when the tiba was lengthened 30% or more, retardation of enchondral growth was evident, which persisted from the time of completion of lengthening to near skeletal maturity. It is postulated that unphysiologically increased pressure on the growth plate due to excessive bone lengthening may be closely related with the inhibition of enchondral growth.