Circumferential Defects Research Articles

Research progress of circumferential tracheal reconstruction via tissue-engineered trachea

Tissue engineering, as a new technology, provides a new avenue for the reconstruction of circumferential tracheal defects, which has always been a tremendous challenge for surgeons around the world. Recently, technologies such as decellularization, 3-dimensional printing, electrospinning and cell sheet have significantly enhanced the chondrification. Implantation of epithelial cells or transplantation of epithelial cell sheets also has accelerated the process of epithelialization. And pedicle muscle flap proved to be a reliable strategy for vascularization of tissue-engineered trachea. But it is still a huge challenge to achieve circumferential tracheal functional reconstruction. The key difficulty lies in how to simultaneously realize the functional regeneration of cartilage, blood vessels and epithelial tissues of tissue-engineered trachea. Therefore, how to integrate the above schemes and finally realize segmental tracheal reconstruction needs further research. This article reviews the research progress of repairing circumferential tracheal defects based on tissue engineering technology.

Local Defect Detection of Ferromagnetic Metal Casing Based on Pulsed Eddy Current Testing

Remote-field eddy current testing (RFECT)-based methods have been widely used in conductive pipe evaluation. However, the response signals of RFECT are affected both by the casing thicknesses around the driver coil and in the vicinity of the pick-up coil, making it difficult to invert and separate the thicknesses around the coils. Moreover, the relative permeability difference between the near-field and the remote-field zones causes a further deviation in the thickness inversion. To avoid these problems, a near-field pulsed eddy current testing method is proposed for defect evaluation. Time-domain transient features, which can be applied for defect detection, are analyzed based on the theoretical data of pulsed eddy current testing. A prototype of the testing apparatus and a defective ferromagnetic metal casing are designed to verify the feature performance for defect evaluation. The experimental results indicate that the time-related features are sensitive to circumferential defects and insensitive to the axial defects, and the magnitude-related feature is sensitive to both the circumferential and axial defects. Therefore, the magnitude-based method can be used to detect the local defects of ferromagnetic metal casings.

Peri-İmplant Kemik Defekti Tipinin Yerleştirme Torku ve Rezonans Frekans Analizi Üzerine Etkisi: İn Vitro Çalışma

Objective: The aim of the present study is to investigate the effects of different peri-implant bone defects on primary stability and the correlation between insertion torque (IT) and resonance frequency analysis (RFA) measurements. Material and Methods: Fourty implant beds were prepared in artificial bone blocks using the 3D surgical guide. Implant osteotomies were divided into 5 groups (n=8) according to defect type: i) no peri-implant bone defect (control), ii) a dehiscence defect, iii) a fenestration defect on the middle part, iv) a fenestration defect on the apical part and v) a circumferential defect. Implants were inserted by using a surgical drilling unit with torque control and RFA measurement were done. Results: IT values for the control group were significantly higher than the other groups (p<0.001). The results of IT measurements for dehiscence defect group were significantly greater when compared to fenestration and circular defect groups (p<0.01). Implant stability quotient (ISQ) values for the control group were significantly higher than other groups (p<0.05). In addition, the ISQ values for the dehiscence defect group were significantly lower when compared to fenestration defect groups (p<0.001), and ISQ values for the circular defect group were significantly lower than any other groups (p<0.001). IT values and, ISQ values are moderately correlated (p=0.013, r=0.388). Conclusion: The location of peri-implant bone defect affects RFA measurements more than IT. However, IT seems to be correlated with bone implant contact. Therefore, in the case of peri-implant bone defect, IT measurement may be preferred for evaluation of primary stability.

Acquired Benign Tracheoesophageal Fistula: An Alternative Tracheoplastic Technique.

We present a case of surgical management of a tracheoesophageal fistula (TEF) following prolonged intubation. After transverse tracheal division and retraction of the distal stump, direct closure of the esophageal defect and repair of the membranous tracheal defect using a synthetic bioabsorbable patch were performed, followed by interposition of muscle flap between the suture lines and tracheal reconstruction. Large TEFs, without tracheal stenosis or circumferential airway defect, associated with marked peritracheal inflammation, may be treated with this alternative tracheoplastic technique in patients deemed not suitable for tracheal resection and anastomosis.

Comparative evaluation of two collagen-based biomaterials with different compositions used for bone graft: An experimental animal study

A large number of materials with different compositions and shapes have been proposed and studied for the purpose of bone tissue regeneration. Collagen-based materials have shown promising results for this application, with improved physicochemical properties. The aim of the present in vivo animal study was to evaluate and compare two commercially available collagen-based biomaterials for bone regeneration, with these being implanted in circumferential bone defects created in the calvarium of rabbits. Twenty rabbits received bilateral parietal osteotomies, performed with the aid of a 6.5 mm diameter trephine. Two groups were created: the BC group, where the defect was filled with a scaffold composed of 90% bovine bone particles and 10% porcine collagen, and the EG group, where the defect was filled with a scaffold composed of 75% hydroxyapatite particles of bovine origin and 25% bovine collagen. Ten animals were sacrificed at 30 days and another 10 at 45 days after implantation, and the samples were processed and histologically analyzed. In the evaluations of the samples at 30 days, no important differences were found in the results. However, in the samples at 45 days after surgery, the EG group showed better results than the BC group samples, mainly in terms of the amount of bone matrix formation (P < 0.0001) and the volume in area measured in each sample, where the EG group had a value 65% higher than that in the BC group samples. Based on the results obtained, we conclude that the amount of collagen and the particle characteristics present in the composition of the scaffolds can directly influence the amount of neoformation and/or bone regeneration.

The combination of anterolateral thigh perforator flap and other flaps for repairing the extreme circumferential defects on the limb

To investigate the effectiveness of the combination of the anterolateral thigh perforator (ALTP) flap and other flaps for repairing the extreme circumferential defects on the limb. Between October 2016 and June 2019, 9 patients with the extreme circumferential defects on the limb were admitted, which resulted by degloving injury, including 8 males and 1 female with a median age of 42 years (range, 32-65 years). The etiology involved twist injury in 5 cases, traffic accident in 2 cases, and high voltage electric injury in 2 cases. The location of the defects was left forearm in 2 cases, right forearm in 3, left foot in 3, and right foot in 1. The injected wound bed followed by the exposure of bone, joint, tendon, and blood vessel. The dimension of defects was 25 cm×20 cm to 40 cm×28 cm. The period between the injury and admission was 1-12 hours (mean, 5 hours). All contaminated wounds were taken thorough and radical debridement and covered by the vacuum sealing drainage device during the emergency operation. The ALTP flap and the other one flap were tailored according to the dimension of the wound when the wound surface became granulating, including the thoracodorsal artery perforator (TAP) flap in 3 cases, superficial inferior epigastric artery perforator flap in 3 cases, superficial circumflex iliac artery perforator flap in 3 cases. And the donor site was primary closure. After operation, all the flaps survived except 1 case of partial necrosis at the edge of TAP flap and healed after secondary skin grafting, and the wounds in the donor and recipient areas healed by first intention. All patients were followed up 14-24 months (mean, 16 months). The shape of the flap was satisfactory and the texture was soft. There was no abnormal hair growth and obvious pigmentation during the follow-up. Only linear scar was left in the donor area, there was no complication such as abdominal wall hernia, and the activity of hip and knee was not affected. The functional reconstruction of upper limb and ankle was satisfactory, and the disabilities of the arm, shoulder, and hand (DASH) score was excellent in 4 cases and good in 1 case; the American Orthopaedic Foot and Ankle Association (AOFAS) score was excellent in 3 cases and good in 1 case. ALTP flap combined with different flaps can reconstruct the circumferential extreme defects after limb damage in one-stage, which can achieve limb salvage to the greatest extent.

Local random flaps for cervical circumferential defect or tracheoesophageal fistula reconstruction after failed gastric pull-up: Two case reports

BACKGROUNDTotal pharyngo-laryngo-esophagectomy with a reconstruction of gastric pull-up is the most common treatment method for patients with multiple primary upper digestive tract carcinomas, such as hypopharyngeal carcinoma with thoracic esophageal carcinoma. However, neck circumferential defect and tracheoesophageal fistula after gastric necrosis are still challenging problems for surgeons and patients.CASE SUMMARYThis case report presents 2 patients who underwent reconstructive surgeries using 4 local random flaps with a split thickness skin graft in the first case, and 6 local random flaps in the second case to close the circumferential defect and tracheoesophageal fistula after failed gastric pull-up. Both patients achieved good swallowing function and could take solid diet without dysphagia postoperatively.CONCLUSIONFor selected patients, local random flaps (with a split thickness skin graft) can be a simple and reliable solution for reconstructing tracheoesophageal fistula or cervical circumferential defect after gastric necrosis, especially when the necrosis extends below the thoracic inlet.

Diagnostic Accuracy of Cone Beam Computed Tomography in Identifying Peri-implantitis-Like Bone Defects Ex Vivo.

This pilot study aimed to assess the diagnostic accuracy of CBCT in identifying peri-implantitis-like bone defects in cadavers. Three cadaver dental arches treated with the Thiel embalming method were used. Three different types of peri-implant bone defects (buccal dehiscence, two- to three-wall defects, and circumferential defects) were prepared on 15 implants. Defect depths and lengths were identified clinically using a periodontal probe, radiologically by means of CBCT images, and histologically with a micrometer using an optic microscope. Peri-implant bone defect morphology evaluated using CBCT images matched the clinical defect configuration (100% accuracy). CBCT assessment demonstrated lower values in defect depth and defect length when compared with the clinical evaluation. A statistically significant difference in defect depth (0.35 ± 0.45 mm; P = .037) was recorded between the clinical and CBCT data. Regarding defect length, a statistically significant mean difference of 0.81 ± 0.83 mm (P = .003) was noted between the clinical and CBCT data. Similarly, a mean difference of 1.09 ± 1.52 mm was recorded between the defect length assessed histologically and the CBCT data (P = .031). No statistically significant differences were observed between the other evaluated variables. CBCT is a reliable tool for peri-implantitis diagnosis and treatment planning, though the underestimation of defect severity may affect the prognosis and clinical decision-making. Clinicians need to be flexible in establishing prognoses and treatment based on CBCT assessment.

Equations for gap-spanning design of underground cast iron pipes lined with thermosetting polymeric liners

Polymeric spray and cured-in-place-pipe liners have attracted the attention of water utilities as alternatives for renovation of deteriorated cast iron pipes. Circumferential defects, in the form of existing gaps, ring fractures or failed joints, may exist in cast iron pipes and they may significantly influence the performance of the lined pipes under applied loads. Literature review showed that limited research has been conducted to investigate the effect of circumferential defects. This paper aims to comprehensively examine the mechanical performance of polymer lined cast iron pipes with circumferential defects, using finite element analyses, and derive equations based on the finite element results for engineering design. Three different failure modes, namely, lining through existing gaps in pressurized host pipes, formation of gaps for pressurized lined pipes subjected to axial movements, and pressurized lined pipes with ring fractures under bending, are comprehensively studied. After validation of the developed numerical models for each of the failure modes, parametric studies were conducted considering different pipe properties, liner properties, loading conditions and interface properties. Equations were then derived based on the numerical results using non-linear regression for the three failure modes to facilitate the use of the results in practice. It was found from this study that for all three modes a reduction in the ratio of the cast iron pipe modulus to liner modulus will result in an increase in the normalized maximum stress, which is defined as the ratio of the maximum stress to internal pressure in the liner. This effect is most significant for formation of gaps for pressurized lined pipes subjected to axial movements and pressurized lined pipes with ring fractures under bending. It was also found that by increasing the friction coefficient or reducing the ratio of liner wall thickness to pipe diameter, the normalized maximum stress in the liner increases. Among the three failure modes, the normalized maximum stress in the liner for formation of gaps for pressurized lined pipes subjected to axial movements was affected the most.

Creation of a rat lymphedema model using extensive lymph node dissection and circumferential soft tissue resection: Is this a reliable model?

The medical demand for lymphedema treatment is huge since the disease mechanism remains unclear, and management are difficult. Our purpose was to develop a reliable lymphedema model mimicking the clinical scenario and allows a microsurgical approach. Male Lewis rats weighing 400 to 450 g were used to create lymphedema with groin and popliteal lymph node dissection and creation of 5 mm circumferential skin defect (n=6). A skin incision was made and closed primarily for control group (n=5). Evaluation included indocyanine green (ICG) lymphangiography 1 and 2months postoperatively, volume difference between bilateral hindlimbs measured using micro-CT, and the skin was harvested for histological evaluation 2months postoperatively. Larger volume differences present in the lymphedema group (17.50 ± 7.76 vs. 3.73 ± 2.66%, p < .05). ICG lymphangiography indicated dermal backflow only in the lymphedema group. Increased thickness of the epidermis was noted in lymphedema group (28.50 ± 12.61 μm vs. 15.10 ± 5.41 μm, p < .0001). More CD45+ (35.6 ± 26.68 vs. 2.8 ± 4.23 cells/high power field [HPF], p < .0001), CD3+ (38.39 ± 20.17 vs. 9.73 ± 8.62 cells/HPF, p < .0001), and CD4+ cell infiltration (11.7 ± 7.71 vs. 2.0 ± 2.67 cells/HPF, p < .0001) were observed in the lymphedema group. Collagen type I deposition was more in the lymphedema group (0.15 ± 0.06 vs. 0.07 ± 0.03, p < .0005). A rat lymphedema model was successfully established. The model can be applied in lymphedema related research.

Long-term lower urinary tract sequelae following AUS cuff erosion.

To examine the rate of lower urinary tract complications (LUTC) and urinary diversion (UD) after artificial urinary sphincter (AUS) explantation with the acute reconstruction of AUS cuff erosion defects. We performed a retrospective study of patients who underwent in-situ urethroplasty (ISU) for AUS cuff erosion from June 2007 to December 2020. Outcomes included LUTC (urethral stricture, diverticulum, fistula), AUS reimplantation, and UD. Defect size was prospectively estimated acutely and a subanalysis was performed to determine the impact of erosion severity (small erosions [<33% circumferential defect] and large erosions [≥33%]) on these outcomes. Kaplan-Meier curves were created to compare survival between the two groups. A total of 40 patients underwent ISU for urethral cuff erosion. The median patient age was 76 years old with a median erosion circumference of 46%. The overall LUTC rate was 30% (12/40) with 35% (14/40) of patients requiring permanent UD. Secondary AUS placement occurred in 24/40 (60%) patients with 11/24 (46%) leading to repeat erosion. On subanalysis, small erosion was associated with improved LUTC-free and UD-free survival but not associated with AUS reimplantation. Lower urinary tract complications are common after AUS cuff erosion and can lead to the need for permanent UD. Patients with larger erosions are more likely to undergo UD and reach this end-stage condition earlier compared to patients with small erosions.

PD04-03 RECONSTRUCTION OF ARTIFICIAL URINARY SPHINCTER CUFF EROSION: DEFECT SIZE PREDICTS PROGNOSIS

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Male Incontinence: Therapy I (PD04)1 Sep 2021PD04-03 RECONSTRUCTION OF ARTIFICIAL URINARY SPHINCTER CUFF EROSION: DEFECT SIZE PREDICTS PROGNOSIS Nathan Chertack, Gregory Joice, Kelly Caldwell, Mehraban Kavoussi, Benjamin Dropkin, Nicolas Ortiz, Adam Baumgarten, Nabeel Shakir, Sarah Sanders, Steven Hudak, and Allen Morey Nathan ChertackNathan Chertack More articles by this author , Gregory JoiceGregory Joice More articles by this author , Kelly CaldwellKelly Caldwell More articles by this author , Mehraban KavoussiMehraban Kavoussi More articles by this author , Benjamin DropkinBenjamin Dropkin More articles by this author , Nicolas OrtizNicolas Ortiz More articles by this author , Adam BaumgartenAdam Baumgarten More articles by this author , Nabeel ShakirNabeel Shakir More articles by this author , Sarah SandersSarah Sanders More articles by this author , Steven HudakSteven Hudak More articles by this author , and Allen MoreyAllen Morey More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000001968.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: In-situ urethroplasty (ISU) has been proposed in conjunction with device explant as an acute management strategy after artificial urinary sphincter (AUS) cuff erosion. Previous studies have not shown a clear relationship between extent of erosion and long-term prognosis. We hypothesize that more extensive erosions are associated with higher rates of lower urinary tract complications (LUTC) and increased need for urinary diversion (UD). METHODS: We performed a retrospective study of patients who underwent ISU for AUS cuff erosion from June 2007 to December 2020 with a minimum of 90-day follow up. Patients were stratified into two groups based on the degree of urethral erosion determined endoscopically at the time of device explant - mild erosions (<33% circumferential defect) and major erosions ( >33%). Outcomes included LUTC, AUS reimplantation, and UD. LUTC was defined as urethral strictures, diverticulum, fistulas, and erosions of a secondary AUS. UD was defined as suprapubic tube placement with or without urethral ligation or ileal conduit creation. Kaplan-Meier curves were created to compare outcomes between groups. RESULTS: A total of 40 patients underwent ISU for urethral cuff erosion and met the follow-up criteria. Median patient age was 76 years old with median erosion defect size of 46% (IQR: 20-50%); 15 men (37.5%) had mild erosions and 25 (62.5%) had major erosions. The overall LUTC rate was 53.5% with significantly fewer complications noted with mild erosions (28.6% vs 65.4%, p=0.002). Ultimately, 35.0% of patients required permanent UD with decreased rates in the case of mild erosions (13.3% vs 48.0%, p=0.04). On Kaplan-Meier analysis, mild erosion was associated with improved LUTC-free and UD-free survival but not associated with AUS reimplantation. CONCLUSIONS: Prognosis after AUS cuff erosion is associated with size of the urethral defect. Patients with extensive cuff erosion are at high risk for LUTCs and permanent UD. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e50-e50 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Nathan Chertack More articles by this author Gregory Joice More articles by this author Kelly Caldwell More articles by this author Mehraban Kavoussi More articles by this author Benjamin Dropkin More articles by this author Nicolas Ortiz More articles by this author Adam Baumgarten More articles by this author Nabeel Shakir More articles by this author Sarah Sanders More articles by this author Steven Hudak More articles by this author Allen Morey More articles by this author Expand All Advertisement Loading ...

Consequences of Peri-Implant Bone Loss in the Occlusal Load Transfer to the Supporting Bone in terms of Magnitude of Stress, Strain, and Stress Distribution: A Finite Element Analysis.

Methods Three models of a single internal connection bone level-type implant inserted into a posterior mandible bone section were constructed using a 3D finite element software: one control model without marginal bone loss and two test models, both with a circumferential peri-implant bone defect, one with a 3 mm high defect and the other one 6 mm high. A 150 N static load was tested on the central fossa at 6° relative to the axial axis of the implant. Results The results showed differences in the magnitude of strain and stress transferred to the bone between models, being the higher strain found in the trabecular bone around the implant with greater marginal bone loss. Stress distribution differed between models, being concentrated at the cortical bone in the control model and at the trabecular bone in the test models. Conclusion Marginal bone loss around dental implants under occlusal loading influences the magnitude and distribution of the stress transferred and the deformation of peri-implant bone, being higher as the bone loss increases.

Efecto regenerador del ácido hialurónico en defectos óseos circunferenciales en ratas albinas Wistar.

Objective: To determine the regenerating effect of hyaluronic acid on circumferential bone defects in albino Wistar rats. Material and Methods: An experimental type study was designed and carried out with 15 albino male Wistar rats, 4 months old and weighing between 250 and 350 grams. Two circumferential bone defects 3mm in diameter and 0.8mm deep were created in the calvaria of the parietal bone (on both sides of the midline). One defect was filled with a demineralized bone matrix (control group); while the other defect was filled with the combination of a demineralized bone matrix plus hyaluronic acid (experimental group). Five experimental rats were euthanized at 30, 60 and 90 days after surgery and they were histologically evaluated following the parameters proposed by Heiple. Results: The experimental group presented a better degree of bone regeneration at 30 and 60 postoperative days. Conclusion: Hyaluronic acid is effective in bone regeneration of circumferential bone defects.

The History of Engineered Tracheal Replacements: Interpreting the Past and Guiding the Future.

The development of a tracheal graft to replace long-segment defects has thwarted clinicians and engineers alike for over 100 years. To better understand the challenges facing this field today, we have consolidated all published reports of engineered tracheal grafts used to repair long-segment circumferential defects in humans, from the first in 1898 to the most recent in 2018, totaling 290 clinical cases. Distinct trends emerge in the types of grafts used over time, including repair using autologous fascia, rigid tubes of various inert materials, and pretreated cadaveric allografts. Our analysis of maximum clinical follow-up, as a proxy for graft performance, revealed that the Leuven protocol has a significantly longer clinical follow-up time than all other methods of airway reconstruction. This method involves transplanting a cadaveric tracheal allograft that is first prevascularized heterotopically in the recipient. We further quantified graft-related causes of mortality, revealing failure modes that have been resolved, and those that remain a hurdle, such as graft mechanics. Finally, we briefly summarize recent preclinical work in tracheal graft development. In conclusion, we synthesized top clinical care priorities and design criteria to inform and inspire collaboration between engineers and clinicians toward the development of a functional tracheal replacement graft.Impact statementThe field of tracheal engineering has floundered in recent years due to multiple article retractions. However, with recent advances in biofabrication and tissue analysis techniques, the field remains ripe for advancement through collaboration between engineers and clinicians. With a long history of clinical application of tracheal replacements, engineered tracheas are arguably the regenerative technology with the greatest potential for translation. This work describes the many phases of engineered tracheal replacements that have been applied in human patients over the past 100 years with the goal of carrying forward critical lessons into development of the next generation of engineered tracheal graft.

A new longitudinal mode guided-wave EMAT with periodic pulsed electromagnets for non-ferromagnetic pipe

L(0,2) Longitudinal mode guided wave shows great advantages for pipe inspection as it can be almost non-dispersive at certain frequency range and is sensitive to the circumferential defects. In this paper, a new plug-in longitudinal mode guided-wave EMAT with periodic pulsed electromagnets (PPEMs) is proposed for small non-ferromagnetic pipe inspection. The new guided-wave EMAT is designed with coil-only configuration, which consists of a periodic pulsed electromagnet and a periodic pulser/receiver coil. Both numerical simulation and experimental results validate it has good performance on generating and receiving L(0,2) mode guided wave in non-ferromagnetic pipes. Comparing with the GW EMAT with periodic permanent magnets (PPMs) in traditional design, the signal amplitude of the guided wave can be significantly enhanced with using the new GW EMAT with PPEMs.

Timing of pyloric stenosis and effectiveness of endoscopic balloon dilation after pyloric endoscopic submucosal dissection.

There have been studies on risk factors for stenosis after pyloric endoscopic submucosal dissection (ESD). However, the most appropriate strategies for the management of cases with these risk factors have not been established. This study aimed to investigate post-ESD management by evaluating the timing of stenosis and the effectiveness of endoscopic balloon dilation (EBD) after pyloric ESD. We retrospectively reviewed cases of pyloric ESD. We first reassessed risk factors for stenosis in multivariate analysis and receiver operating characteristic curve and defined patients with the identified risk factors as the risk group. The primary outcome was the timing of stenosis in the risk group assessed by the Kaplan-Meier method. We reviewed 159 cases with pyloric ESD and observed pyloric stenosis in 25 cases. Cases with circumferential mucosal defect≥76% were identified as the risk group. The stenosis-free probability in the risk group was 97% (95% confidence interval [CI]: 79-100%), 94% (95% CI: 76-98%), and 85% (95% CI: 66-93%) on days 7, 14, and 21, respectively. It decreased every week thereafter and did not significantly change after day 56. Twenty-three stenosis cases, except for conservative improvement, including six whole circumferential pyloric ESD cases, were improved by EBD without complications. Post-ESD stenosis often developed from the third to the eighth week. In all pyloric ESD cases, including whole circumferential pyloric ESD cases, pyloric stenosis was improved following EBD without complications.

Simulation and Practice of Guided Wave Test Method in Circular Rod

Guided wave mode and dispersion curve in the circular rod are analyzed, and the time domain waveform of Φ20mm*2m circular rod is analyzed. Though finite element simulation and experiment, the variation law of reflection coefficient of different guided wave modes is analyzed. The L(0,1) is consistent with the change trend of F(1,1) modes for axial and circumferential defects, and the simulation results of L(0,1) modes are consistent with the test results.

ID: 3526513 RISK FACTORS FOR STENOSIS AFTER ENDOSCOPIC SUBMUCOSAL DISSECTION OF LARGE LESIONS OF THE RECTUM

The development of stenosis in the rectum after endoscopic submucosal dissection (ESD) is one of the most frequently delayed complication, ranging from 4.2 to 19.7 % of the resections of large rectal lesions. Circumferential mucosal defect greater than 90% seems to be only independent predictor of stenosis. Morphology and size have not shown relation with the occurrence of strictures.

Effectiveness of Silicon Platelet-Rich Fibrin and Autologous Bone on Bone Regeneration in Rabbit Calvarian Defects: A Radiological and Histological Study

Repairing bone defects in oral surgery often requires the use of bone regeneration techniques. Silicon is an element that has been employed as regeneration material in several studies. In our study, silicon was combined with autologous bone and platelet-rich fibrin (PRF) membranes to analyse the behaviour of this element in bone regeneration. Four circumferential defects were created in the cranial vault of five New Zealand rabbits. The following elements were applied to the regeneration of the defects: (P): PRF; (S): silicon and (B): autologous bone, with the following distribution of study groups: Group 1 (PSB); Group 2 (PS); Group 3 (SB) and Group 4 (CONTROL): unregenerate group. The animals were sacrificed after 3 weeks. Computed microtomography studies (μ-CT) were carried out, as well as histomorphometric ones. The ANOVA statistical test was used with a Bonferroni post-hoc test to compare the results (p ≤ 0.05). Radiologically, groups PSB and SB were better as far as quantity and percentage of healthy bone observed, but not significantly compared to the control group. The PS group was significantly worse. The histological test revealed that the PSB group was the one to present the largest area, percentage and perimeter of mineralised bone. On evaluating the forming bone (osteoid), no difference was observed across the groups with the exception of the bone perimeter, where the SB group was significantly better. The bone height variable showed no significant differences. In conclusion we can state that the combination of PRF, autologous bone and silicon provides good results at 3 weeks whilst the PS group shows the worst results. This highlights the importance of autologous bone forming part of the graft material in order for the bone to mineralise.