| Fractures of the clavicle are common and mainly caused by trauma. It often happened in young men. We can make the diagnosis accurately by combination of the story, physical examination, X-ray and CT. In recent years, with the development of a variety of internal and external fixation technology and new concepts of treatment, the research of clavicle fractures have been improving. Between2and5%of all fractures affect the clavicle in adult and it about10%to15%in children, which makes it one of the most frequently broken bones of the human body. The incidence of clavicle fractures for adults is29-64/100.000/year. Young men who are lower than30-year-old and older people those are more than70years old are the two high-risk group of clavicle fracture.Most frequently, the middle third of the clavicle is affected. Lateral fractures account for about15%, whereas medial clavicle fractures are relatively rare. The clavicle is S-shaped with a medial convexity and a lateral concavity. The acromial end of the clavicle is flat, its middle is round and the sternal end shows a triangular profile. The middle third is the thinnest part of the clavicle and is located directly under the skin with no soft tissue or muscle attachment. Thus, it is vulnerable to direct and indirect trauma. This explains the high frequency of fractures in the middle third.There are many methods for the treatment of clavicle fractures, and it include non-operative and surgery. Although, there are many literatures relative to the treatment of clavicle fractures had been reported, it is still no conclusive data to show which is the best methods. The incidence of nonunion was less than1%from non-operative methods whereas three times higher in the surgery methods from the data that had been reported in1960by Neer and other professors, so that fractures of the clavicle were considered to be a domain of non-operative treatment for a long time. Kim have found that the nonunion rate of non-operative treatment was significantly higher than the previous data, and the satisfaction was not high for the patients in recent years. With the development of various internal fixation materials, more and more clavicle fractures are treated by surgery, especially open reduction and internal fixation.Internal fixations include intramedullary fixation systems and plate system, such as the Knowles needle, Herbert nails, Steinmann pin, flexible intra-medullary nail. Plate osteosynthesis is still the standard method for the surgical treatment of clavicle shaft fractures. The steel shaped plate, compression plate, anatomical plates and reconstruction plates and locking plates are usually used. Plate fixation not only has the tension band effect, but also it can be anti-rotation, good stability. Especially, it can be safe, that are different from the intramedullary fixation pin which may migrate to inside and injury the tissue nearly. However, there are also some complications for the ORIF, such as periosteal stripping, destruction of the blood supply and stress shielding, plate fracture and nonunion. Because of their good toughness, reconstruction plate have been usually applied in the treatment of clavicle fracture according to the shape of the bones. Although superior plating has been cited as biomechanically preferable, anterior plating produces less hardware prominence, allows for longer AP screw purchase, and avoids screw trajectories toward the inferior neurovascular structures. Pending definitive biomechanical and clinical comparisons, plating position is currently determined by surgeon preference. Locking compression plate are applied in some of the osteoporotic clavicle fractures and severe comminuted fracture for their strengths and stability. In order to reduce the injury risk of the inferior neurovascular structures when the surgeon place the screw intra-operative, can we use the locking plate for single cortical fixed?Additionally, the external fixation may be an options methods for open fracture or chronic osteomyelitis and nonunion cases, but the traditional external fixation are often a large structure, sharp edge impact dressing, and even cause harm to patients or health care workers. A clinical study found that the locking compression plate for its angle screw placement and its stability can be used as external fixator in the treatment of tibia open fracture. So we hypothesize that the locking compression plate can be applied as external fixator for the treatment of clavicle open fracture or nonunion.In recent years, with the computer image processing, the growing development of digital technology, three-dimensional simulation technology and finite element analysis method were also more and more used in various fields, which also greatly promoted the development of the biomedical field. One of the computational methods that has received wide acceptance in orthopedics research is the finite element analysis (FEA). In this technique, three dimensional models of bone implant construct are converted into finite elements with simulated physiological loads applied to analyse and predict the outcome of surgery. The common fixation devices, rehabilitation equipment and medical equipment design are based on bone stress and strain, and the application of finite element analysis and3-D simulation techniques analysis of the human skeleton provide a powerful tool for making the scientific design of medical devices accurately and rapidly.This paper address these clinical problems, combined with three-dimensional finite element analysis method, to study the controversy that the reconstruction plate for treatment of middle clavicle fracture placement from a mechanical point of departure, locking plate fixation in different cortical layers, locking plate used as external fixation for the treatment of open clavicle fracture or nonunion, and discuss its clinical biomechanical significance.Objective1. Establish a three-dimensional finite element model of the clavicle.2.To explore the biomechanical properties of mid-shaft clavicle, oblique fractures fixed with reconstruction plates, comparing anterior to superior plate position through finite element(FE) analysis, and therefore to provide scientific foundation for clinic application.3.To study the biomechanical properties of the three methods to treatment clavicle fracture by the finite element analysis, the locking plate double cortex locked and single-layer cortical locking and reconstruction plate bi-cortical fixed. To provide a theoretical reference for clinical application.4.To explore the biomechanical of locking compression plate used as external fixation by the finite element analysis.Methods1. Three dimensional (3D) model of human clavicle was reconstructed from two dimensional computed tomography (CT) image using3D model reconstruction software (MIMIC10.01, Materialise, Belgium). The CT image dataset was obtained by scanning the upper limb of a single male subject in one medical centre. Then analysis the stress and strain distribution by testing in axial compression. The model will be confirmed in accordance with previous reported results and clinical observation of phenomena.2.3D FE model of the mid-shaft clavicle, oblique fractures with different position fixations was developed. Each construct was tested in axial compression, bending, internal, and external torsion. The different position fixations were compared for von Mises distribution, and the maximum comprehensive displacement were also compared.3. Fixation of three simulated mid-shaft fractures was undertaken using a combination of mono-cortical locked, bi-cortical locked and bi-cortical non-locked plating methods in FE model. Samples were then tested via three-point bending conditions, bending stress, and the internal or external torsion. The three different fixation methods were compared for von Mises distribution, and the maximum comprehensive displacement were also compared.4. An opening of5mm gap was simulated by removing a bone piece from the mid-shaft part of the clavicle. The three dimensional models of both implants including locking compression plate and traditional external fixation were designed according to the manufacturers’ specifications using computer aided design (CAD) software (Solidworks2010, Dassault Systems, Massachusetts, USA).Then axial compression and clockwise twist and counterclockwise to reverse of the three conditions were simulated in the same load and constraint conditions. We will evaluate the maximum equivalent stress, the largest integrated displacement of the two external fixation methods.Results:1. The three-dimensional finite element model reconstructed has been compared with the the traditional biomechanical experimental results and clinical observations phenomenon, and it proved to be effective and reasonable.2. The evaluation index data was no difference between anterior and superior plate position under compression loading; During the bending, internal, and external torsion loading conditions, the maximum stress on the anterior fixtures was significantly greater than on the superior fixtures, but the fracture fragments displacement and the maximum stress on the fracture fragments was no difference.3.(1)The three fixations all appear to some internal fixation stress concentration, but the biggest stress of mono-cortical locked was significantly higher than the other two methods in all conditions;(2) displacement:the displacement on the fracture fragments was no difference under axial compression condition, however, the mono-cortical locked fixed was greater than bi-cortical fixation in condition of internal rotation;4.(1) Under compression condition:the maximum stress to the external fixation plate and screw was concentrated in the outer most distal screw; and the maximum stress of the traditional external fixator fixed was at the outside of a steel needle. Not only the equivalent displacement fracture fragments but also the maximum stress of external fixation device, and the maximum stress of the fracture fragments, the statistical data showed that there was no significant difference.(2) clockwise torsion conditions and counterclockwise rotation conditions for the shoulder joint:both of the locking compression plate used as external fixation and the traditional external fixator appear stress concentration, and the maximum stress is mainly concentrated in the external fixation plate and needle, but there were no no significant difference between the stress and the maximum equivalent displacement of this two different fixations.Conclusions:1. We have established a three-dimensional finite element model successfully in this experiment, which was a real reaction clavicle geometry and can be analog collarbone biomechanical properties, and it has the advantages of reusable than traditional methods of experimental mechanics.2. For the mid-shaft clavicle, oblique fractures, reconstruction plates fixed on the anterior was more prone to stress concentration than superior fixtures, and this prompt that the biomechanical stability of superior fixtures is better than the anterior fixtures.3. Application locking plate fixation for mid-shaft clavicle fractures, the mono-cortical locking was prone to be more stress concentration than the general reconstruction plate and the bi-cortical fixed locked, and this results suggests that we should use the bi-cortical fixed in clinical applications.4. In this study, the biomechanical properties between the locking compression plate used as external fixation and the traditional external fixation for the treatment of clavicle were analysed by the three-dimensional finite element method, the statistical analysis showed that there was no significant difference in both fixed stress distribution. Compared to the traditional external fixator, the locking compression plate has the advantage of small external contours,, better stability and so on. Therefore, in the view of a biomechanical, locking compression plate used as external fixator was an alternative methods to the treatment of open fractures, nonunion, and the chronic osteomyelitis. |
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