Narrow Results

Wrist arthrodesis is exceptionally performed in children. The main indication is severe wrist flexion contracture resulting from Volkmann's ischaemia or spasticity. In such cases, a proximal row carpectomy is usually necessary to allow the wrist to be positioned in neutral position. In young children, it is essential to preserve the distal radius growth plate, to prevent physeal closure. In these very particular indications, with high stresses along the stretched palmar soft-tissues, Kirschner wire fixation provides poor stability, and plate fixation is contra-indicated. Radio-metacarpal external fixation is an excellent alternative, preserving the distal radius growth plate and offering sufficient stability. This technique was used in a seven-year-old girl suffering from Volkmann's ischaemic contracture, treated by first carpal bone resection and subsequent arthrodesis with radio-metacarpal external fixation. Bone healing was achieved in three months, with a five years follow-up preservation of the distal radius growth plate.

The purpose of this study is to investigate the effects of normal, moderate and high doses of fluoride on rat epipyseal growth plate and surrounding bone, and to compare it with controls. In order to achieve this, 80 rats were divided into five groups (n: 16/group) and treated with 0, 1.2, 3, 50 and 100 ppm fluoridated water since birth (Groups I to V, respectively). Four rats from each group were sacrificed at 6th, 9th, 12th and 16th weeks for radiological and histopathological examinations.

There was no significant variation on programmed cell death of cartilagenous components of the growth plate and chondroid matrix histopathologically between control group and fluoride-treated groups. But, minimal irregularities on the cartilage septum of primary spongiosa were detected in one rat from Group IV and one from Group V. The main histopathologic findings of the rats which were treated with high doses of fluoride were irregular lamella, variation in calcium content, minimally enlarged Haversian canals, focal osteoblastic proliferation, rare zones of woven bone on the diaphyseal cortical bone and secondary spongiosa, increase in ossicle size and minimal focal osteoblastic proliferation on the secondary ossification center. The only consistent radiological finding was relative widening and late partial fusing of the epiphyseal growth plates of high-dose treated groups at 16th week.

As a result, high doses of fluoride did not directly affect chondrocyte morphology of growth plate on young rats. More sophisticated techniques would be beneficial for further investigations on this subject.

The growth plate is a structure formed of cells called chondrocytes; these are arranged in columns and provide the elongation of bone due to their proliferation and hypertrophy. In each column, we can see chondrocytes in their proliferating state, which are constantly dividing, and in hypertrophic state, which grow in a nearly spherical shape. These cells express different proteins and molecules throughout their half-life and exhibit a special behavior depending on their local mechanical and biochemical environments. This article develops a mathematical model that describes the relationship of geometry, growth by proliferation and hypertrophy, and vascular invasion with biochemical and mechanical factors present during endochondral ossification.

The growth plate is a cartilaginous structure located in the metaphysis of long bones, characterized histologically by its stratification and columnar arrangement. It is responsible for assuring longitudinal growth. Evaluation of growth plate histological characteristics has been traditionally performed using qualitative observation; however, some quantitative approaches have been reported using complex techniques. Here, we propose a simple quantitative images based analysis in order to evaluate objectively columnar arrangement within growth plate. For this, we defined six descriptors that were condensated in a geometric tensor. This tensor could be used as a single parameter to evaluate the growth plate organization. Validation of the tensor was performed with growth plate microphotographs of three healthy species (rat, pig and rabbit) and an abnormal one (Csf1^tl/Csf1^tl rat) found in specialized literature. According to our results, the descriptors and the tensor give a complete picture of the organization of the growth plate, reflecting the expected stratification and columnar arrangement of the cells within the tissue. This methodology could be a reliable tool for evaluation of growth plate structure for research and diagnostic purposes, taking into account that it can be easily implemented.

Long bone growth relies on the continuous bone formation from cartilaginous tissue (endochondral ossification). This process starts in the central region (diaphysis) of the forming bone and short before birth, ossification starts in bone extremes (epiphysis). A cartilaginous region known as the growth plate is maintained until adolescence between epiphysis and diaphysis to further contribute to longitudinal growth. Even though there are several biochemical factors controlling this process, there is evidence revealing an important regulatory role of mechanical stimuli. Up to now approaches to understand mechanical effects on ossification have been limited to epiphysis. In this work, based on Carter's mathematical model for epiphyseal ossification, we explored human growth plate response to mechanical loads. We analyzed growth plate stress distribution using finite element method for a generic bone considering different stages of bone development in order to shed light on mechanical contribution to growth plate function. Results obtained revealed that mechanical environment within the growth plate change as epiphyseal ossification progresses. Furthermore, results were compared with physiological behavior, as reported in literature, to analyze the role of mechanical stimulus over development. Our results suggest that mechanical stimuli may play different regulation roles on growth plate behavior through normal long bone development. However, as this approach only took into account mechanical aspects, failed to accurately predict biological behavior in some stages. In order to derive biologically relevant information from computational models it is necessary to consider biological contribution and possible mechanical–biochemical interactions affecting human growth plate physiology. Along these lines, we propose the dilatatorial parameter k used by Carter et al. should assume different values corresponding to the developmental stage in question. Thus, reflecting biochemical contribution changes over time.

Chondrocytes in the growth plate undergo a relatively linear differentiation process. The progression of a chondrocyte from the proliferative stage to the hypertrophic stage is governed by complex interactions with the extracellular matrix within which it resides. A network of peptides, ion channels, and second messengers affects the transcription of certain genes that are ultimately translated into peptides which control cellular activity. Much effort has been invested into replicating this environment under in vitro conditions. It has been found that the three-dimensional (3D) cell culture is a more accurate representation of the in vivo environment in comparison to the traditional monolayer culture. It has also been found that a variety of stimuli may be used to induce the proliferation and differentiation of chondrocytes; one such stimulus is the mechanical stimulation of chondrocytes embedded in a 3D Gelfoam sponge. Chondrocytes are obtained from the chicken sternum. After the cells are cultured and cyclically loaded, mRNA levels of various mechanosensitive genes are quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR). Mechanical stimulation has been shown to upregulate the expression of type X collagen mRNA in early hypertrophic chondrocytes. The entire process, beginning with the obtainment of chondrocytes and ending with the quantification and interpretation of gene expression, is detailed in the following chapter.

Physeal injury is not uncommon in pediatric orthopedics, with Salter–Harris type II (SH II) fracture being the most common type that may lead to growth arrest and eventually limb shortening. Therefore, research on SH II fracture will hold great potential to benefit children with such an injury. This chapter outlines the creation of a partial growth plate defect model in rabbits that mimicks a SH II fracture for applications in various growth plate or articular cartilage research topics. The establishment of an SH II rabbit model described in this chapter provides some relevant and applicable evaluation methods. This model will be helpful for research on the biology of premature physeal closure during injuries or the exploration of new biomaterials for physeal reconstruction.