| Lewis once said in1973that the most artistic operation was nasal cosmetic surgery in all operation. In the early60s of this century, expanded polytetrafluoroethylene successfully developed by the W.L.Gore company, the clinical application of that in artificial blood vessels made very great success in1969,and obtained the FDA license, and was widely used in cardiovascular operation, abdominal wall reconstruction, ligament repair, hernia repair and so on. Part of the developed countries used polytetrafluoroethylene for cosmetic operation in the early80s, but the domestic had used it since1995.PTFE is a polymer material. Its physical and chemical properties are stable, non-toxic, resistant to high and low temperature from-200℃to-250℃,and chemical corrosion.It is the ideal prosthesis materials Within10um～30um superfine porous structure for nose augmentation operation.It has the good compatibility with the surrounding tissue which is not absorbed in the body, not easy to deformation, non carcinogenic and allergic reactions, not easy to breed a variety of microorganisms,and can be conveniently shaping. It combines with the graft bed and brakes that not lead to chronic inflammation,has sufficient hardness to support organization, also has enough toughness to obtain natural and lifelike effect. It is permeable to X-ray in vivo.Its thermal and electrical conductivity is low, and it can be taken out conveniently when a problem occurs.In addition, if the operation is not exhausted, it can repeatedly use more than ten times to reduce the waste of materials through high pressure disinfection.Expanded polytetrafluoroethylene are carving by a variety of methods, and the advantages are not identical. According to the different shapes,it can be divided into short-leaf type that is applicable to the patients with simple nasal root, Liu Yexing that applicable to the patients with the nasal root and low back, L type that applicable to the patients that nasion nasal dorsum and nasal tip all need to improve.According to the composition of prosthetic materialit can be divided into three Methods.One of methods is that all use the reinforced bulk ptfe material, engraved L type of prosthesis.After assured the length of the prosthesis,ventral arm at the intersection is wedge resection, and the depth is to reach at least the2/3of phantom thickness that not cut into length of two, the long one is as the long arm in the L type of prosthesisas from gold nose root to tip performance points,the short is the short arm of the L type prosthesis from the length of the columella to subcutaneous segment. Both sides of the short arm amputate, retaining only the width about2mm, benting toward the ventral side,using the nylon suture linein on junction between the short and long arm, and making the angle of ninety degrees in short-long arm in L prosthesis. One of methods is that all use ePTFE reinforced materials, but not carved into L type of prosthesis. Part of Columella exist independently, that willow leaf type prosthetic combine with nasal septum. The last approach is that put silicone prosthesis and expanded polytetrafluoroethylene simultaneously,which attached to the tip of the nose or nasal dorsum of silicone prosthesis.There are other carving method paying more attention to detail.If carving into the spindle it makes the appearance more natural. But the problem after rhinoplasty activity has not been attention. When Silicone prosthesis put double V notch, the nose can easily bob around, but the bridge of the nose can not swing,and can prevent prosthesis sliding down.In order to prevent the complications,if put prosthesis on the area of tip nose not less than4mm×4mm and nasal root use V design,it makes the nasal prosthesis ventral side cut into concave with lateral nasal cartilage. Ship-like prosthesis use multichip suture bulk PTFE, that makes the material more saving.With the rhinoplasty extensively, it has more and more high requirement of postoperative nasal shape from the patients. A survey found,63%patients after rhinoplasty noticed tip activity decreased,30%was not satisfactory about the operation effect,27%said they would not touch the nose in public, and7%said they didn’t rub the nose and wipe the nose, even when the cold. That is to say, patients are not only concern about the improvement of static appearance of postoperative nasal, but also the requirements of dynamic appearance close to nature as possible. So how to improve the activity of postoperative nasal has attracted more and more attention.The postoperative effect is mainly affected by the condition of the patient, surgery technology, selection of operation and the effect of prosthesis material. The choice and the carving method of prosthetic material,the most objective factor,largely influences the postoperative shape.In this paper, according to the shape of the prosthesis after improvement it is named Capricorn,which means Capricorn, a sheep-shead fish animal. Because the Capricorn prosthesis resembles the sheepshead fish animal, so they choose this name.The Carving method is following.Choosing15mm*70mm*5mm PTFE, on the long side of midline slightly oblique incision rotating blade material,obtained two section with a right angle trapezoid. One of the material put On the subject of nose back to determine the radian of nasal root and the length of the stem in subject. The starting become A, the lower become B, tip is C.Straight cross section is isosceles trapezoid in the finishing materials.C which is the upper and lower boundary, open3mm down beside a wedge resection to tetrahedral-shape material, and make the L prosthesis. According to the determined nasal root arc,the wide of A is cut arc to form a part of prosthetic at the root. From the end of material B with isosceles trapezoid section to A cut in a rectangula shape, they adjust the length and thickness according to the condition of subject. The narrow face, and both sides on1/3of the upper middle and lower material uniform, that straight down to remove material, shape like an V,that was the angle from20to45, and the vertex falls on the narrow edge, outside the mouth is located in the below vertex. Flip material, wide face, triangular notch along the edge downward wedge resection material, not cut through the material.The three dimensional finite method is a research method of biomechanics, very simple and practical, and reflects the ability of the false physical properties particularly good. Although the need of some simplifying assumptions to unavoidable in finite element analysis of the past,so there is certain error with the simulated object, but the overall trend of its biomechanical properties can better reaction, analysis of the obtained data are of practical clinical significance, thus make supplement and validation good for the research method of experimental biomechanics.Mechanical analysis include TPLnose measurement data,the double V phantom measurement data,capricorn phantom measurement data,as carving method. Device include the personal computer, hardware Intel core I32370M,2.4GHz,8G memory, windows7operating system, Modeling of finite element analysis software AbapusCAE. Geometric model form in Abapus, that need70*15*5parts, and cut according to the nose prosthesis data, and save project files. Linear elastic material attribute assignment for materials. The elastic modulus589Pa, and Poisson’s ratio of0.4. Establishment of section properties using solid isotropic material properties assigned to the default values and individual parts and assembly parts.the analysis step is following. Using analysis of the general static to establish initial analysis step, changing the initial iterative value for0.1to reduce the increment value. Define the boundary condition of load in the initial step, using mechauical mechanical type and Displacement/rotation types establish the boundary conditions. Choice of prosthesis in1/3long constraint three displacement direction. In the same position and area time establish mechanical type as prssure, the amplitude of the load of1force.Distribution of unifom, analytical field distribution of ramp.Using network technology to divide hexahedral mesh, and modify the best distribution grid.The establishment of job send and see the results, in the visualization view,it can view the nephogram of stress. Adjust the degeneration scale at the same value in the view, cut screenshot and save it as a comparison chart.After comparing with chart, tip of prosthesis displace in coronal plane.Displacement of Capricorn prosthesis is more than double v nasal prosthesis,which is greater than the traditional carving method. The sagittal displacement of tip is that Capricorn prosthesis is more than nasal prosthesis of traditional carving method.L expanded polytetrafluoroethylene prosthesis in augmentation rhinoplasty is used more and more, compared with silicone prosthesis, many experienced doctors tend to choose the expanded. First of all, its good biocompatibility, micro porous structure can provide space for the surrounding tissue, angiogenesis, and tissue around long together, and thus can provide more stable prosthesis position, won’t be no postoperative prosthesis floating or falling off like the silicone prosthesis in vitro. Secondly, after that,it is no hard straight lines like solid silicone rubber filling,and a hard look of simple sense. Although the more and more use of clinical expanded, but the analysis on the carving method in domestic lack. This allows surgeons to see the carving be clear, and facilitates learning and application.The deficiencies of PTFE are the high price and promotion difficult,using the carving method of Capricorn prosthesis sculptured with a polytetrafluoroethylene material can carve out2Capricorn prosthesis,and the mechanical analysis of3D model can be mechanical assessment of new engraving progress,saving resources,avoid waste.From the analysis results of3D modeling mechanical we can see, both sagittal and coronal activity, the Capricorn prosthesis is superior to traditional L polytetrafluoroethylene prosthesis and double Vcarving method, that prove that the Capricorn prosthesis can make activity of postoperative recipient tip to improve, so that nose is more closer to nature after augmentation rhinoplasty,which improve the satisfaction of augmentation rhinoplasty, and the carving method can prevent prosthesis sliding in. We can also learn from other carving method,which applied to the Capricorn prosthesis in order to more perfect, such as the word V incision in prosthesis top and nasal colum.The Institute has completed the Capricorn prosthesis rhinoplasty.patient is pleased with satisfaction Postoperative nasal soft lines and a good tip activity. sagittal activity has not reached the ideal state may be related to tissue edema after14days.Research of Capricorn we need to increase the number of cases to study the mechanics of tip from the general population to improve Capricorn prosthesis,which would make the nose more simulate,and we also need to further seriously to psychological changes of patients. |
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