Gómez-Benito MJ, García-Aznar JM, Kuiper JH, Doblaré M. A 3D computer simulation of rapid fracture formation: influence of the rigidity of the external fixator. J Biomech Eng. 2005;128(3):290–9. The process of total regeneration of the bone may depend on the angle of inclination or fracture. While bone formation usually spans the entire healing process, in some cases, the bone marrow in the fracture healed two weeks or less before the final remodeling phase. [Citation needed] The results of this work quantified the effects of the initial healing phase on the outcome of healing in order to better understand biological and mechanobiological mechanisms and their use in the design and optimization of treatment strategies. It is also demonstrated by a simulation that no callus development is necessary for fractures where bone segments are nearby. This finding is consistent with the concepts of primary and secondary bone healing. The X-rays examined were the first images obtained after the removal of the Ilizarov full-wire circular fixator. The vast majority of Ilizarov fixators are removed in an outpatient clinic, with AP taken after removal and lateral X-rays immediately after.

The AP and lateral views were reviewed in all cases, with all 46 image pairs anonymized and randomized before being evaluated by six reviewers. Three were trauma counsellors, two were consultants specializing in musculoskeletal radiology and one was a trauma and limb reconstruction fellow. An example of the sign « callus fracture » (Fig. 2) was given to the examiners with clear written instructions for identification. An example of an established hypertrophic non-union (Fig. 1) was also provided, and examiners were allowed to recognize if they thought it was present, but this did not count as the « Callus fracture » sign that was present. We used the term callus fracture sign to describe the extent of fracture cleavage beyond the boundaries of the cortex, but within the boundaries of the callus. After the bone fracture, blood cells accumulate next to the site of injury.

Shortly after the fracture, the blood vessels constrict and stop further bleeding. Within a few hours, extravascular blood cells form a clot called a hematoma [5], which serves as a model for callus formation. These cells, including macrophages, release inflammatory mediators such as cytokines (tumor necrosis factor alpha (TNFα), interleukin-1 family (IL-1), interleukin 6 (IL-6), 11 (IL-11) and 18 (IL-18)) and increase blood capillary permeability. Inflammation peaks about 24 hours and ends in seven days. Thanks to tumor necrosis factor receptor 1 (TNFR1) and tumor necrosis factor receptor 2, TNFα is involved in the differentiation of mesenchymal stem cells (derived from bone marrow) into osteoblasts and chondrocytes. Stromacell-derived factor 1 (SDF-1) and CXCR4 are involved in the recruitment of mesenchymal stem cells. IL-1 and IL-6 are the main cytokines for bone healing. IL-1 promotes the formation of calluses and blood vessels. IL-6 promotes the differentiation of osteoblasts and osteoclasts. [4] All cells in the blood clot degenerate and die. In this area, fibroblasts replicate. Within 7 to 14 days, they form a loose aggregate of cells, interspersed with small blood vessels called granulation tissue.

[Citation needed] Osteoclasts move to reabsorb dead bone ends and other necrotic tissues are removed. [6] The mechanobiological regulation described by Prendergast et al. [1997] [17] was used to determine the type of tissue differentiation under applied mechanical stress (Fig. 1-A). As a rule, high mechanical stimuli lead to the formation of fibrous tissue, intermediates promote the formation of cartilage tissue, and lower levels lead to bone formation. This mechanobiological regulation has been smoothed and modified based on the work of Sapotnick and Nackenhorst [39] to prevent abrupt changes in tissue differentiation categories (Fig. 1-B) [39]. The usual course of treatment with circular fixation is the gradual destabilization of the frame before removal. These results suggest that the callus rupture line is an indicator that stability may be insufficient, and reversing this standard protocol at a period of increased frame stability before further fracture stability tests should reduce the risk of developing a hypertrophic non-combination. The day corresponding to the beginning of bone bypass for three different callus thicknesses (d = 3, 5 and 7 mm) is shown in Fig. 6, where the MSC diffusion coefficient varies between 0.01 and 10 mm2/day.

The results are presented for three different values of the modulus of elasticity of the granulation tissue (e.g. = 0.1, 1 and 2 MPa). It should be noted that for the thickness of the callus of 1 mm, the bone bridge in the simulations does not occur in 120 days, regardless of the height of the MSC diffusion coefficient and the granulation tissue that the modulus of elasticity took into account in this series of simulations. Thus, no results are displayed for the thickness of the callus of 1 mm. In general, the start of bypass surgery for models with a thicker callus is faster. Faster MSC migration and stiffer granulation tissue also speed healing, resulting in faster formation of boney bridges. We used a well-established model of the bone healing process presented by Lacroix & Prendergast (2002) [30] to design a parametric study to computationally quantify the effects of the initial healing phase on the outcome of healing. We examined the performance of our simulation approach and FE model to determine whether the results are consistent with previous computer studies and experimental observations. In the basic model, our numerical simulations predict that cartilaginous cal is reached in 2-3 weeks from the beginning of the healing process, that the bone bridge occurs in 1 month, and that the complete bone callus is developed in less than 2 months. This development schedule is entirely consistent with clinical observations, as well as with the results of previous numerical studies [5, 21, 30]. In addition to the chronology, the tissue formation model in our simulation is comparable to other studies [21, 30, 45].

Bone formation begins first in the outer region of the original callus, far from the fracture site, where mechanical stimuli are at their lowest local levels [45, 46]. Gradually, this initial bone formation provides mechanical support to the fracture site, thereby reducing mechanical stimuli and inducing bone formation in other regions of the callus, such as near the bone marrow and fracture space [30, 46]. Inflammation – this stage extends from the moment of fracture to the formation of a bone callus. At the breaking point between the fragments, a hematoma is formed. The role of hematoma is uncertain; It can form a framework for the growth of fibrous tissue and provide some stability due to the formation of fibrin. Fracture results in a typical inflammatory reaction with the release of lysosomal enzymes from the extremities of the fracture and soft tissues. The bone at the fracture becomes necrotic with a hypoxic and acidic environment. Osteoclasts are mobilized and the absorption of the hernia ends. X-ray technology, the fracture ends become less opaque and their edges become indistinct. In the coming weeks, the soft callus will become harder. After about 2-6 weeks, this hard callus is strong enough for the body part to be used.

The point at which a fracture of the tibiaf is united is an important step in treatment, but is of particular importance in patients treated with an Ilizarov frame, as it determines when the fixative can be removed. In our unit, as in others, this happens when there is a set of clinical features: bypass of calluses on X-rays; the patient wears painlessly; and there is no clinically detectable movement at the fracture site. As soon as it is assumed that a fracture has united, the frame is energized and then separated. If there is no movement between the manually energized rings, it is likely that there was no movement at the breaking point and the frame was then removed. These criteria are similar to those described by Sarmiento [9]. Hard callus – during this stage, the soft callus is gradually transformed by enchondral ossification into woven bone when cartilage is present, or by mineralization of a new osteoid. Mineralization is first radiologically visible 1 to 3 weeks after injury, initially as ill-defined fuzzy mineralizations that combine to form a bone callus. Eventually, a trabecular pattern develops as the callus becomes more organized.

This can take weeks to months and is usually accompanied by the restoration of the endostal and periosteal blood supply. The shape and definition of the edge of the new bone should also be evaluated. A useful rule of thumb is that if you can`t follow the outline of the new bone with a sharp pencil, it is considered ill-defined and should be considered new and active. If the edge is well defined, it indicates a chronic process. A smooth edge indicates a chronic lesion, which is completely reconstructed and probably inactive. A well-defined irregular margin indicates a chronic, but probably active lesion that is likely to be mild to moderately aggressive. Productive lesions often include active and inactive areas of bone formation, and in such cases the lesion should be classified according to the most aggressive new bone. The rate of change of a lesion is a very useful indicator of the degree of aggressiveness or malignancy. Serial X-rays taken at intervals of 7 to 14 days can be used to assess suspicious lesions, especially if the initial results are ambiguous. Aggressive lesions usually show a rapid rate of change with clear evidence of progression of osteolysis and bone formation over a relatively short period of time.