| In otorhinolaryngology field, there is no ideal technique to deal with the deformity and dysfunction due to the laryngotracheal framework defect. Doctors and scientists used to reconstruct these cases by autotransplant . allotransplant and artificial grafts transplant. However, autogeneous grafts are associated with problems of limited supply . donor-site morbidity and poor moldability; Most alloplastic grafts are failed to immune rejection response and infection; there is a long way to go for reconstructing the laryngotracheal defects by tissue engineering technique. Therefore, it has become an interesting and difficult issue to reconstruct the laryngotracheal framework defects; it becomes a main aim for otolaryngology and head and neck doctors to find a new approach to resolve these problems. This study attempt to repair and reconstruction the defects of laryngotracheal framework with Ni -Ti shape memory alloy and reconstituted bone xenograft (RBX) respectively in order to find an ideal method and material to reconstruct laryngotracheal framework defects.In tracheal surgery field, there are many cases of long segment defect of trachea due to various causes, for example, after tumor resection operation. For the cases of the defect less than 6cm, the doctors can adopt the end to end anastomosis technique, but there also exist some complication of anastomosis site dehiscence and stricture. For the cases of the defect longer than 6cm, it is impractical to take the end to end anastomosis. Ni - Ti SMA is widely been used in clinical medicine because of it's characteristics of good shape memory, ultraflexibility^ antifatigue and antierosion. But most of researchers use it as intratracheal stent which usually accompany with the following complications: formation of granulation tissue, displacement of the Ni - Ti SMA net, the injury of the tracheal wall and massive haemorrhage, etc. Therefore, it is a controversy whether it is fit to use Ni - Ti SMA net to treat the benign laryngotracheal stenosis patients. To avoid the complication following the using of Ni - Ti SMA net as intratracheal stent, the first and second part of this study aims to probe into the feasibility of using Ni - Ti SMA net designed and made by the researchers to form trachea shape structure combined Ni - Ti SMA with skin so as to reconstruct the long segment defect of trachea by two stage operation.Bone morphogenetic protein (BMP ) has good potential in treatment for bone defect as it can induce mesenchymal cells to differatiate into chondrocytes and bone cells so to form new bone. The reconbinationed bone xenograft (RBX ) was prepaired by defatted and decalcified bone xenograft as a carrier combined with BMP (1:20), which has potential of bone inducement and noobvious immune rejection response. It has beem authorized to apply the RBX in orthopaedics clinical practice, furthermore, it has the advantage of abundant source and being easy to get. The third part of this study aimed to repair the defect of laryngotracheal framework with RBX.Materials and methodes1 The designing and knitting of the Ni-Ti SMA net5 adult mongrels were taken from the experimental animal center of the forth military medical university (weight: 18 ±0.5kg). The cervical trachea was anatomized and it's diameters was measured in order to decide the the diameters of Ni-Ti SMA net. Then according to the parameters the model was made and the Ni-Ti SMA net was knitted .2 Using the Ni-Ti SMA net combined with skin to reconstruct long segment defect of trachea(1) part 1 Formation of the trachea shape structure by combining the Ni-Ti SMA net with skin2 adult mongrels(weight : 18 ± 0.5kg ) provided by the experimental animal center of the forth military medical university were taken. The Ni-Ti SMA net was made by the researchers. The animals were anaesthetized with 3% pentobarbital sodium and two parallel longitudinal incisions with 5cm in length and 8cm to each other were made. The Ni-Ti SMA net was inserted subcutaneously,then the surrounding tissue was sutured to the Ni-Ti SMA net in order to fix the Ni-Ti SMA net and eliminate the subcutaneous empty space, by all these steps a trachea shape structure was formed.(2) part 2 Using the Ni-Ti SMA net combined with skin to reconstruct long segment defect of trachea by one stage2 adult mongrels(weight : 18 ± 0.5kg ) provided by the experimental animal center of the forth military medical university were taken. The Ni-Ti SMA net was made by the researchers. Afre the experimental animals were anaesthetized with 3% pentobarbital sodium, a 5cm segment of cervical trachea was resected and a skin tube was formed to reconstruct the defect of trachea, the Ni-Ti SMA net was planted into the site between the skin tube and the cervical muscle tissue and the skin tube was sutured to the Ni-Ti SMA net to keep it from collapsing.(3) part 3 Using the Ni-Ti SMA net combined with skin to reconstruct long segment defect of trachea by two stage5 adult mongrels(weight : 18 ± 0.5kg ) provided by the experimental animal center of the forth military medical university were taken. The Ni-Ti SMA net was made by the researchers to substitute for the tracheal cartilage and the skin tube was made for the tracheal mucosa in order to form a new trachea shape structure to repair the mongrel dogs' trachea defects by two stage operation. First stage a 5cm segment of cervical trachea was resected and a skin tube was formed to reconstruct the defect of trachea, while a silicic T tube was put into the skin tube tomaintain the shape of airway. Second stage the Ni-Ti SMA net was planted into the site between the skin tube and the cervical muscle tissue. Then the breath and swallowing functions of the mongrels were observed and the computer tomography(CT) scan and fibrotracheoscope examination were taken so as to find out the location of the Ni-Ti SMA net and the effect of tracheal defect repair.3 Experimental study on thyroid cartilage defect repair with reconstituted bone xenograft32 New Zealand white rabbits were divided into three groups: blank control group planted with muscle, bone xenograft control group planted with bone xenograft and RBX experimental group planted with RBX. The models of a 0. 5cm X 0.5cm thyroid cartilage defect were established and then muscle, bone xenograft and RBX were implanted into the three groups respectively. After 4, 8> 16 weeks and 12 months , the osteogenesis and the repair effect were analyzed by gross observation , computer tomography(CT) scan and hematoxylin and eosin (HE ) staining of tissue sections.Results1 The designing and making of the Ni-Ti SMA netThe mean diameter value of cervical trachea is 2.0cm. Considering the "C" shape Ni-Ti SMA net was used as external stent and the skin tube with a thickness of 2mm will be fixedinterior to the Ni-Ti SMA net, we designed and made the Ni-Ti SMA net with 2. 5cm in diameter and 5cm in length and with a cranny of 4mm.2 Using the Ni-Ti SMA net combined with skin to reconstruct long defect of trachea(1) part 1 Formation of the trachea shape structure by combined the Ni-Ti SMA net with skinThe 2 experimental animals breathed and swallowed normally with congestion and swelling physical signs in the operation sites. After 4-5 days, the Ni-Ti SMA net which had been implanted subcutaneously punctured the skin and exposed in air.(2) part 2 Using the Ni-Ti SMA net combined with skin to reconstruct long segment defect of trachea by one stageAfter the operation there were no signs that indicated surgical infection. The experimental animals keeped coughing after regaining consciousness. The second day dyspnea symptom was developed and became more and more serious gradually. The two experimental animals died for choking on the second and the third day respectively. We found the skin tube become swelling > cadaverous and necrotic partially by autopsy, while there was abundant secretion existing in the reconstructed trachea shape structure.(3) part 3 Using the Ni-Ti SMA net combined with skin to reconstruct long segment defect of trachea by two stageAfter first stage operation, the five experimental animals breathed and swallowed normally and there were no signs that indicated surgical infection. The necks of the experimental animals moved freely.After second stage operation, the 4 experimental animals breathed and swallowed normally and there were no signs that indicated surgical infection. The necks of the experimental animals moved freely. CT scan showed the reconstructed airways were wide enough, the implants were fixed perfectly before decannulated. After decannulation the fibrotracheoscope examination showed the airways were wide enough and were columniform and the airway walls did not collapse. There were hair growing in the airway to various extend. After the experimental animals were put to death, the fibrotracheoscope examination showed the airway did not become narrow, but there were hair and phlegm existing in the reconstructed airways. We found that the skin tube and the external muscle tissue connected closely through the mesh of the Ni-Ti SMA net by autopsy. The other 1 dog was failed to decannulate due to the infection.3 Experimental study on thyroid cartilage defect repair with reconstituted bone xenograftThere was no new-formed bone in the blank control group and the BX control group. The defects in the control group were repaired with scar tissue and the bone xenografts were completely absorbed after 16 weeks. There existed new-formed bone in the defect site in the RBX experimental group. The thyroid cartilage defects were repaired by new formed bones perfectly in the RBX group.Conclusions1 The shape and the supporting strength of Ni-Ti SMA net are...
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