Secondary fracture healing in long bones leads to the successive formation of intricate patterns of tissues in the newly formed callus. The main aim of this work was to quantitatively describe the topology of these tissue patterns at different stages of the healing process and to generate averaged images of tissue distribution. This averaging procedure was based on stained histological sections (2, 3, 6, and 9 weeks post-operatively) of 64 sheep with a 3 mm tibial mid-shaft osteotomy, stabilized either with a rigid or a semi-rigid external fixator. Before averaging, histological images were sorted for topology according to six identified tissue patterns. The averaged images were obtained for both fixation types and the lateral and medial side separately. For each case, the result of the averaging procedure was a collection of six images characterizing quantitatively the progression of the healing process. In addition, quantified descriptions of the newly formed cartilage and the bone area fractions (BA/TA) of the bony callus are presented. For all cases, a linear increase in the BA/TA of the bony callus was observed. The slope was greatest in the case of the most rigid stabilization and lowest in the case of the least stiff. This topological description of the progression of bone healing will allow quantitative validation (or falsification) of current mechano-biological theories. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J. Orthop. Res. 28: 1440Res. 28: -1447Res. 28: , 2010 Keywords: bone healing; tissue pattern; osteotomy; animal model; averaged image Secondary fracture healing of long bones proceeds via the formation of a callus. 1-3 The task of the callus is to stabilize the fracture fragments resulting in a reduction of the strains in the fracture area, allowing the bone ends to be united. Usually the process of secondary fracture healing is subdivided into three main phases: the inflammatory phase, the reparative phase, and the remodeling phase. 4 These phases, however, are not well separated in time, and significant overlap can occur between them. During the inflammatory phase, vascular damage leads to hematoma formation. The reparative phase includes revascularization and the formation of fibrous tissue and cartilage, and new bone is formed at the periosteal side of the cortex by intramembranous ossification. [4][5][6] Soft callus bridging occurs via cartilage, which is later transformed into bone by endochondral ossification. During the remodeling phase, lamellar bone replaces woven bone, the callus is resorbed, and finally the original shape of the bone is restored. [7][8][9][10] To understand the progression of the healing process, and in particular the influence of the mechanical environment, a number of animal experiments have been performed. In these experiments, either "static" fixators with different degrees of stability [11][12][13][14] or "dynamic" fixators, which induce micro-movement to stimulate callus formation, 15,16 were used. These experiments d...
Read the fine print: Biomolecular binding events can be counted with a readout system based on compact disc (CD) pickup technology. An immunoassay of C‐reactive protein was performed by microcontact printing of antibodies onto a support, autometallography, and imaging by a CD reader mounted on an optical microscope (see picture). The dynamic range was four orders of magnitude with a detection limit of 1 pM.
A simple approach to the mechanical modulation of layer-by-layer (LbL) films is through manipulation of the film assembly. Here, we report results based on altering the salt concentration during film assembly and its effect on film rigidity. Based on changes in film rigidity, cell adhesion characteristics and transfection activity were investigated in vitro. LbL films consisting of reducible hyperbranched poly(amide amine) (RHB) have been implemented along with DNA for investigating fibroblast adhesion on [RHB/DNA]n/2 films with varying rigidities. The rigidity was varied by changing the ionic concentration of the deposition solution between 0.01 M NaCl and 1.0 M NaCl. Molecular force probe (MFP) measurements were performed to measure the apparent Young’s modulus, EAPP, of the films in situ. Cell adhesion and stress-fiber characteristics were investigated using total internal reflectance microscopy (TIRF-M). The average cell peripheral area, fiber density and average fiber length during 5 days of cell growth on films with either low (below 2.0 MPa) or high (above 2.0 MPa) film elastic modulus were investigated. Transfection studies were performed using gfpDNA and SEAP-DNA to investigate if changes in cell adhesion affect transfection activity. Furthermore, cell proliferation and cytotoxicity studies were used to investigate cellular viability over a week. The results have shown that surface modification of bioreducible LbL films of controlled thickness and roughness promotes cellular adhesion, stress-fiber growth and increased transfection activity without the need for an additional adhesive protein pre-coating of the surface or chemical cross-linking of the film.
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