Improved healing of microvascular PTFE prostheses by induction of a clot layer: an experimental study in rats

This study was undertaken to test the hypothesis that the induction of a clot layer on the graft surface of microvascular polytetrafluoroethylene (PTFE) prostheses might improve their healing. PTFE microvascular prostheses (n = 18), mechanically roughened PTFE microvascular prostheses (n = 18), and Chitosan-impregnated PTFE microvascular prostheses (n = 18) (all prostheses: length 1 cm, inside diameter 1.5 mm, fibril length 30 microns) were implanted into the abdominal aortas of rats and were evaluated at 3 days (n = 3), 10 days (n = 3), 3 weeks (n = 6), and 6 weeks (n = 6) with regard to the presence or absence of a clot layer and with regard to the amount of graft healing. All untreated PTFE prostheses were never found to be covered with a clot layer, only scarcely with some platelets, and showed poor neoendothelial healing; even at 6 weeks after implantation, there was only endothelial cell coverage near the anastomotic sides (coverage = 19 +/- 4 percent). The endothelial cells were present directly on the graft surface. In contrast, both the roughened and the Chitosan-impregnated PTFE prostheses were completely covered with a thin clot layer upon implantation and demonstrated significantly better neoendothelial healing (endothelial cell coverage at 6 weeks = 76 +/- 22 percent and 75 +/- 18 percent, respectively; p less than 0.001); moreover, in these prostheses, the endothelial cells were present on a matrix of smooth-muscle cells, which covered the graft surface completely. These results confirm our hypothesis that the induction of a clot layer on the graft surface of microvascular PTFE prostheses improves their healing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Amniotic membrane transplantation in the treatment of persistent epithelial defect on the corneal graft

It has been shown that amniotic membrane transplantation (AMT) improves healing of the epithelium defects as it serves as a basement membrane for endothelial cells growth, prevents inflammatory cell infiltration and reduces apoptosis in keratocytes. Having in mind the healing properties of AM we investigated the efficacy of AMT in persistent epithelial defect (PED) on the corneal graft. 80 corneal grafts were prospectively followed up for presence of PED 10 months after surgery. PED was detected in 12 cases (15%) having surgery for: rejected graft (n = 4), keratoconus (n = 3), keratoconus following PK on a second eye (n = 3), corneal perforation (n = 1) and Stevens-Johnson keratopathy (n = 1). Epithelial defect (ED) developed 14 +/- 7 days after surgery in 10 cases and 1.5 month in other two. All patients were primarily conservatively treated with subconjuctival steroids and artificial tears for 10 days and systemic steroid therapy if needed after, until the period of 2 weeks. 4 patients were healed. Since ED was unresponsive to all previous treatments for more than 2 weeks, one layer of AM was placed on the corneal lesion in 5 patients, and in 3 cases of deep PED several layers of AM were placed. Healing of the defect was obtained in 7/8 (87.5%) eyes. In 1 patient second AM transplantation was necessary. Mean epithelization time was 2 weeks (range 1-3 weeks) in monolayer and 3 weeks (range 2-4 weeks) for multilayer cases. 5 out of 8 patients retained the same best corrected visual acuity (BCVA) while 3/8 patients improved their vision more than 2 lines. Preoperative corneal thickness of 255 +/- 40 mm increased to 455 +/- 90 mm. AM transplantation facilitates healing of corneal epithelium. PED on the corneal graft unresponsive to conventional treatment can be effectively cured when covered with one or more amniotic membrane layers.     

Reconstruction of rat femoral veins with microvascular prostheses

Synthetic conduits have not been suitable for microvascular reconstruction owing primarily to their high thrombogenicity. Vein replacements are the most vulnerable to thrombosis because of their low shear rates and low pressure. Experimental replacement of microvenous segments with prosthetic segments has shown little success. Recent technological advances in biomaterials and control of thrombogenesis provide the potential for success in the development of venous prostheses. The purpose of this study was to assess the use of nonbiodegradable composite polyurethane microvascular prostheses for reconstruction of rat femoral veins. Rat femoral venous defects of 10 mm were reconstructed with autogenous vein (n = 12), unprocessed plain polyurethane (n = 5), and nonbiodegradable composite polyurethane (n = 31). Patency was evaluated by direct observation and proximal venous milking tests. The patency rate of composite grafts was not significantly different from that of isotopic vein (p = 0.5, Fisher's exact test), and both had higher patency than unprocessed polyurethane (p less than 0.01). Composite grafts were examined sequentially using light and scanning electron microscopy. Grafts were fully endothelialized between the first and third months. The neointimal, neomedial, and neoadventitial layers could be seen more distinctly over time. New opportunities in reconstructive microsurgery may be opened by microvascular prostheses that are complaint and thromboresistant.     

Replantation of fingertip amputation by using the pocket principle in adults

There are several treatment modalities for zone 1 or zone 2 fingertip amputations that cannot be replanted by using microsurgical techniques, such as delayed secondary healing, stump revision, skin graft, local flaps, distant flaps, and composite graft. Among these, composite graft of the amputated digit tip is the only possible means of achieving a full-length digit with a normal nail complex. The pocket principle can provide an extra blood supply for survival of the composite graft of the amputated finger by enlarging the area of vascular contact. The surgery was performed in two stages. The amputated digit was debrided, deepithelialized, and reattached to the proximal stump. The reattached finger was inserted into the abdominal pocket. About 3 weeks later, the finger was removed from the pocket and covered with a skin graft. We have consecutively replanted 29 fingers in 25 adult patients with fingertip amputations by using the pocket principle. All were complete amputations with crushing or avulsion injuries. Average age was 33.64 years, and men were predominant. The right hand, the dominant one, was more frequently injured, with the middle finger being the most commonly injured. Of the 29 fingers, 16 (55.2 percent) survived completely and 10 (34.5 percent) had partial necrosis less than one-quarter of the length of the amputated part. The results of the above 26 fingers were satisfactory from both functional and cosmetic aspects. Twenty of the 29 fingers, which had been followed up for more than 6 months (an average of 16 months), were included in a sensory evaluation. Fifteen of these 20 fingers (75 percent) were classified as "good" (static two-point discrimination of less than 8 mm and normal use). From the overall results and our experience, we suggest that the pocket principle is a safe and valuable method in replantation of zone 1 or zone 2 fingertip amputation, an alternative to microvascular replantation, even in adults.     

Anastomotic stenting in a porcine aortoiliac graft model

The purpose of the study was to evaluate the feasibility of anastomotic stent application in a porcine aortoiliac graft model. In a total of 10 pigs, a polytetrafluoroethylene aortobi-iliac graft was implanted through a midline abdominal incision. The lower edge of the iliac vessel was graft-inverted about 1 mm to produce irregularities at the downstream anastomosis. After transverse graft incision, six stainless-steel stents, six poly-L-lactic acid (PLLA) stents and four PLLA stents with 10% polycaprolactone (PCL) were implanted at the iliac anastomotic site using a 6 mm balloon dilatation catheter. Four anastomotic sites were left untreated. After two weeks, the patency of graft limbs was evaluated by contrast-enhanced computed tomography (CT). Both metal and polymeric stent designs provided adequate flexibility to manoeuvre across the anastomotic site for expansion in the chosen position. After deployment, the stent-arterial wall contact was complete on a macroscopic view. On CT scan, all metal and PLLA-stented graft limbs were free of stenosis, whereas all PLLA/PCL stents were occluded. The non-stented graft limbs showed a stenosis of 50-70%. In summary, this model is feasible to assess preclinically the deployment and patency rate of an anastomotic stent and to test future stent developments.     

Selective recruitment of endothelial progenitor cells to ischemic tissues with increased neovascularization

Tissue ischemia remains a common problem in plastic surgery and one for which proangiogenic approaches have been investigated. Given the recent discovery of circulating endothelial stem or progenitor cells that are able to form new blood vessels, the authors sought to determine whether these cells might selectively traffic to regions of tissue ischemia and induce neovascularization. Endothelial progenitor cells were isolated from the peripheral blood of healthy human volunteers and expanded ex vivo for 7 days. Elevation of a cranially based random-pattern skin flap was performed in nude mice, after which they were injected with fluorescent-labeled endothelial progenitor cells (5 x 10(5); n = 15), fluorescent-labeled human microvascular endothelial cells (5 x 10(5); n = 15), or media alone (n = 15). Histologic examination demonstrated that endothelial progenitor cells were recruited to ischemic tissue and first appeared by postoperative day 3. Subsequently, endothelial progenitor cell numbers increased exponentially over time for the remainder of the study [0 cells/mm2 at day 0 (n = 3), 9.6 +/- 0.9 cells/mm2 at day 3 (n = 3), 24.6 +/- 1.5 cells/mm2 at day 7 (n = 3), and 196.3 +/- 9.6 cells/mm2 at day 14 (n = 9)]. At all time points, endothelial progenitor cells localized preferentially to ischemic tissue and healing wound edges, and were not observed in normal, uninjured tissues. Endothelial progenitor cell transplantation led to a statistically significant increase in vascular density in ischemic tissues by postoperative day 14 [28.7 +/- 1.2 in the endothelial progenitor cell group (n = 9) versus 18 +/- 1.1 in the control media group (n = 9) and 17.7 +/- 1.0 in the human microvascular endothelial cell group (n = 9; p < 0.01)]. Endothelial progenitor cell transplantation also showed trends toward increased flap survival [171.2 +/- 18 mm2 in the endothelial progenitor cell group (n = 12) versus 134.2 +/- 10 mm2 in the media group (n = 12) and 145.0 +/- 13 mm2 in the human microvascular endothelial cell group (n = 12)], but this did not reach statistical significance. These findings indicate that local tissue ischemia is a potent stimulus for the recruitment of circulating endothelial progenitor cells. Systemic delivery of endothelial progenitor cells increased neovascularization and suggests that autologous endothelial progenitor cell transplantation may have a role in the salvage of ischemic tissue.     

Ventral rectus fascia closure on top of mesh hernia repair in the sublay technique

Sublay prosthetic herniorrhaphy has become a widely accepted procedure for incisional hernias. To evaluate the effect of fascia closure on top of mesh repair on infection, and the recurrence rate, the authors reviewed their data regarding herniorrhaphy in the sublay technique. This study was a retrospective analysis of 175 consecutive patients who underwent hernia repair by implantation of prostheses by means of the Stoppa-Rives technique from December of 1994 to December of 2001. All 175 patients had the mesh implanted in the subfascial plane, 130 received a light-weight or heavy-weight polypropylene mesh (Vypro or Prolene) (74 percent), eight had a polyester mesh (Mersilene) (5 percent), and 37 had an expanded polytetrafluoroethylene patch (Gore-Tex) (21 percent). After sublay mesh positioning, the mesh could not be covered by the fascia in 50 cases; in 31 of these cases, a second mesh was placed into the fascial defect. To evaluate the influence of the fascia closing procedure on top of the sublay mesh, three groups were differentiated: initial fascia closure (n = 125), no fascia closure and concomitant mesh interposition (n = 31), and no fascia closure without mesh interposition (n = 19). After a mean follow-up of 20 months, 11 deep prosthetic infections (8 percent) and 15 hernia recurrences (9 percent) were observed. There was an increased risk of mesh infection when the fascia could not be closed, but there was no influence of fascia closure on hernia recurrence. When the fascia was left open, the placement of a second mesh inlay technique reduced mesh infection. The authors' data give evidence that closing the ventral fascia after mesh repair in the sublay position is beneficial. When the edges of the hernia defect could not be approximated, the suturing of a second mesh into the fascia defect was a useful tool for reducing the prosthetic infection rate; however, no significant influence on hernia recurrence was observed.     

The biomechanical and histopathologic effects of surface texturing with silicone and polyurethane in tissue implantation and expansion.

There has been considerable interest in determining the effect of morphologic alterations of prosthetic surfaces on capsule response in breast surgery. The purpose of this study was to provide a precise, three-dimensional evaluation of soft-tissue response to surface modifications in both implantation and expansion. Expandable 100-cc prostheses were designed with one of three surfaces: textured silicone (Biocell), standard smooth silicone, or polyurethane (Natural-Y, Meme). A new submuscular implantation site in the rabbit was developed. Each animal randomly received a smooth-surface device on one side and either a textured silicone or polyurethane device on the other. In one group of animals, the prostheses were expanded monthly. Capsular response was evaluated monthly in vivo using standardized techniques as well as biomechanical methods for up to 6 months in the expander group (n = 7 to 16) and 8 months in the implant group (n = 7 to 15). Analysis of biomechanical and histologic data revealed that prosthetic surface morphology can specifically alter capsular response. Polyurethane was the only effective surface in preventing capsular contracture in implantation. In expansion, both textured silicone and polyurethane surfaces resulted in significantly less capsular contracture and less resistance to expansion than comparable smooth-surfaced controls. Statistical comparisons reveal that the biomechanical methods utilized in this study provide the most precise and objective method of defining overall soft-tissue contracture around implanted biomaterials.     

Tubular silk scaffolds for small diameter vascular grafts

Vascular surgeries such as coronary artery bypass require small diameter vascular grafts with properties that are not available at this time. Approaches using synthetic biomaterials have been not completely successful in producing non-thrombogenic grafts with inner diameters less than 6 mm, and there is a need for new biomaterials and graft designs. We propose silk fibroin as a microvascular graft material and describe tubular silk scaffolds that demonstrate improved properties over existing vascular graft materials. Silk tubes produced using an aqueous gel spinning technique were first assessed in vitro in terms of thrombogenicity (thrombin and fibrinogen adsorption, platelet adhesion) and vascular cell responses (endothelial and smooth muscle cell attachment and proliferation) in comparison with polytetrafluoroethylene (PTFE), a synthetic material most frequently used for vascular grafts. Silk tubes were then implanted into the abdominal aortas of Sprague-Dawley rats. At time points of 2 weeks and 4 weeks post implantation, tissue outcomes were assessed through gross observation (acute thrombosis, patency) and histological staining (H&E, Factor VIII, smooth muscle actin). Over the 4-week time period, we observed graft patency and endothelial cell lining of the lumen surfaces. These results demonstrate the feasibility of using silk fibroin as a vascular graft material and some advantages of silk tubes over the currently used synthetic grafts.     

Small-calibre vascular grafting into the rat abdominal aorta with biodegradable prostheses

130 Male Wistar rats, 2-3 months old and weighing 250-350 g were operated on to implant biodegradable small-calibre vascular prostheses (length 10 mm; internal diameter 1.5 mm) in their infrarenal abdominal aorta. The mean operation time was 40 min, the mean aortic cross-clamping time 25 min. The early patency rate was 100%, the late patency rate was 97.7%, and the operative mortality was 3.1%. Microscopical examination of the biodegradable prostheses from 1 h up to 1 year after implantation demonstrated reproducible morphological results; in these prostheses a new arterial wall regenerated which had a structure very similar to the normal arterial wall. It was concluded that the rat is an appropriate experimental laboratory animal for testing new types of small-calibre vascular prostheses.     

Exteriorized chronic aorto-caval arteriovenous access shunts in the baboon (Papio cynocephalus)

A chronic arteriovenous (AV) blood access shunt has been developed in baboons. It is composed of silicone rubber tubing extensions bonded to vascular graft polytetrafluoroethylene (ePTFE) cuffs, for creating anastomoses with the distal aorta and inferior vena cava. Following surgical implantation, shunts remain patent for months (X = 9 ± 2.5 months) and provides long-term ex vivo access to non-anticoagulated blood (Mean Blood Flow = 312 ± 69 mL/min).     

Manufacture of small calibre quadruple lamina vascular bypass grafts using a novel automated extrusion-phase-inversion method and nanocomposite polymer

Long-term patency of expanded polytetrafluoroethylene (ePTFE) small calibre cardiovascular bypass prostheses (<6 mm) is poor because of thrombosis and intimal hyperplasia due to low compliance, stimulating the search for elastic alternatives. Wall porosity allows effective post-implantation graft healing, encouraging endothelialisation and a measured fibrovascular response. We have developed a novel poly (carbonate) urethane-based nanocomposite polymer incorporating polyhedral oligomeric silsesquioxane (POSS) nanocages (UCL-NANO?) which shows anti-thrombogenicity and biostability.We report an extrusion-phase-inversion technique for manufacturing uniform-walled porous conduits using UCL-NANO?. Image analysis-aided wall measurement showed that two uniform wall-thicknesses could be specified. Different coagulant conditions revealed the importance of low-temperature phase-inversion for graft integrity. Although minor reduction of pore-size variation resulted from the addition of ethanol or N,N-dimethylacetamide, high concentrations of ethanol as coagulant did not provide uniform porosity throughout the wall. Tensile testing showed the grafts to be elastic with strength being directly proportional to weight. The ultimate strengths achieved were above those expected from haemodynamic conditions, with anisotropy due to the manufacturing process. Elemental analysis by energy-dispersive X-ray analysis did not show a regional variation of POSS on the lumen or outer surface. In conclusion, the automated vertical extrusion–phase-inversion device can reproducibly fabricate uniform-walled small calibre conduits from UCL-NANO?. These elastic microporous grafts demonstrate favourable mechanical integrity for haemodynamic exposure and are currently undergoing in-vivo evaluation of durability and healing properties.     

In vivo biostability of four types of arterial grafts with impervious walls; their haemodynamic and pathological characteristics

We describe the haemodynamic and pathological characteristics of four types of impervious arterial prostheses, two alloplastic (Milrathane^® and Gore-Tex^®), and two chemically processed bovine heterografts (Solcograft^® and Solco P^®). They were implanted in the thoracic aortae of dogs for durations of 24 hours, 48 hours, one weeks, two weeks, one month, three months and six months. Haemodynamic analyses showed no relation between the shear rate index, I·_Y, and compliance, C_D. The observed shear rates are 6.5 times lower than those likely to damage the endothelial cell layer. Macroscopic and microscopic observations of explanted grafts showed the presence of obstructive thrombi at the anastomoses of Mitrathane^® grafts as early as one week. Gore-Tex^® grafts develop in the area of anastomoses parietal-thrombi which reorganize and become covered with pseudo-endothelial cells. The bovine heterografts show a similar behaviour. However, whereas Solcograft^® has an irregular thin wall, Solco P^® had improved characteristics except in the graft implanted for three months which demonstrated some manufacturing weaknesses. Both types showed the development of anastomotic pannus covered with endothelial-like cells. All grafts, whether alloplastic or chemically processed, suffered from an absence of healing of the middle part of the prosthesis. The cause of this problem will be found in the analysis of the biochemical and enzymatic reactations between the material used and its physiological surrounding.     

Colonic healing after portal ischemia and reperfusion: an experimental study with oxidative stress biomarkers

This experimental study aimed to evaluate colon healing after portal ischemia followed by reperfusion. Seventy male Wistar rats randomly distributed in four groups were used: Group 1, colonic anastomosis (n = 20); Group 2, portal ischemia-reperfusion (n = 20); Group 3, colonic anastomosis and portal ischemia-reperfusion (n = 20); and Group 4, control (n = 10). In the postoperative period, these rats were re-allocated into subgroups and lipid peroxidation and protein oxidation plasma levels were evaluated on days 1 and 5 by thiobarbituric acid reactive substances (TBARS) and slot-blotting assays, respectively. A segment of the right colon was also removed for collagen analysis. Both malondialdehyde (MDA) and protein carbonyl levels (oxidative markers of lipids and proteins) presented a significant increase after reperfusion in Group 3 on days 1 (P < 0.002) and 5 (P < 0.0001). In this same group, an extensive inflammatory process showing decreased fibroplasia was observed, with deficiency in collagen deposition on both sides of the anastomosis edges. Taken together, these results indicate that portal congestion followed by reperfusion induces an oxidative stress, which impaired the mechanism of colon anastomotic healing.     

Non-Invasive Monitoring of Temporal and Spatial Blood Flow during Bone Graft Healing Using Diffuse Correlation Spectroscopy

Vascular infiltration and associated alterations in microvascular blood flow are critical for complete bone graft healing. Therefore, real-time, longitudinal measurement of blood flow has the potential to successfully predict graft healing outcomes. Herein, we non-invasively measure longitudinal blood flow changes in bone autografts and allografts using diffuse correlation spectroscopy in a murine femoral segmental defect model. Blood flow was measured at several positions proximal and distal to the graft site before implantation and every week post-implantation for a total of 9 weeks (autograft n = 7 and allograft n = 10). Measurements of the ipsilateral leg with the graft were compared with those of the intact contralateral control leg. Both autografts and allografts exhibited an initial increase in blood flow followed by a gradual return to baseline levels. Blood flow elevation lasted up to 2 weeks in autografts, but this duration varied from 2 to 6 weeks in allografts depending on the spatial location of the measurement. Intact contralateral control leg blood flow remained at baseline levels throughout the 9 weeks in the autograft group; however, in the allograft group, blood flow followed a similar trend to the graft leg. Blood flow difference between the graft and contralateral legs (ΔrBF), a parameter defined to estimate graft-specific changes, was elevated at 1–2 weeks for the autograft group, and at 2–4 weeks for the allograft group at the proximal and the central locations. However, distal to the graft, the allograft group exhibited significantly greater ΔrBF than the autograft group at 3 weeks post-surgery (p < 0.05). These spatial and temporal differences in blood flow supports established trends of delayed healing in allografts versus autografts.     

Experimental microvascular polytetrafluoroethylene grafts: 6-month patency

The efficacy of 1-mm internal-diameter polytetrafluoroethylene as a microvascular prosthesis is unclear. In this study, 8-mm-long segments of this material were implanted into the femoral arteries of 30 rats. Animals were examined every 2 weeks up to 6 months by Doppler ultrasound. Cumulative patency by the life-table method was 86.7 percent at 6 months. There were 26 patent grafts, 2 occlusions, and 2 deaths. Intimal hyperplasia adjacent to the anastomoses was seen in the native arteries. The pseudointima lining the grafts was cellular near the anastomoses but usually acellular in midgraft regions. It is concluded that if early failure does not occur, then good long-term patency is possible with 1-mm polytetrafluoroethylene in this setting and that patency is not dependent on development of a cellular pseudointima. Longer graft segments should be evaluated in future studies.     

The polytetrafluoroethylene-covered stent: a device with multiple potential advantages

The polytetrafluoroethylene (PTFE)-covered stent has emerged in the past year as a device with multiple potential advantages. Its structure (a sandwich composed of a layer of PTFE membrane between two stents) makes this the ideal tool for treating coronary ruptures, and for excluding coronary aneurysms. Furthermore, this device may be useful in the treatment of aortocoronary vein graft stenosis. In the present review, the authors summarize experiences with covered stents, and focus attention on available data on the implantation of PTFE-covered stents in human beings to treat coronary ruptures, aneurysms and aortocoronary vein graft stenosis.     

Comparison of donor-site healing under Xeroform and Jelonet dressings: unexpected findings

Split-thickness skin grafts remain central to the strategy of burn wound treatment. The dressing used to cover the donor wound site has a significant effect on healing parameters. The purpose of this study was to compare split-thickness skin graft donor site reepithelialization under Xeroform and Jelonet dressings. A dermatome was used to cut two consecutive strips of skin from 25 paired donor sites on the thigh, calf, or back of 19 participants. Standardization of the harvest method was achieved by using the same surgeon to harvest the compared skin graft strips, with attention to consistency of dermatome skin-thickness setting, downward pressure, and angle of dermatome approach. A strip of Xeroform or Jelonet was applied to one of each pair of wounds. Epidermal and dermal thickness was measured from biopsy specimens cut at the midpoint of each split-thickness graft strip. The day of final dressing separation was declared the day of complete donor reepithelialization (healing). The mean healing time for Xeroform and Jelonet was 10.4 +/- 2.6 days (n = 25) and 10.6 +/- 2.8 days (n = 25) (p = 0.76) at sites cut to a mean depth of 0.23 +/- 0.08 mm and 0.23 +/- 0.09 mm (p = 0.89), respectively. There was no correlation between graft thickness and healing time for sites dressed with Xeroform (r = 0.17) or Jelonet (r = 0.02). Donors sites reharvested 10 to 21 days after a prior harvest healed an average of 3.1 days earlier than virgin sites (8.4 +/- 1.6 versus 11.5 +/- 2.6 days, p < 0.001), although reharvested grafts were on average 0.05 mm thicker (p = 0.10). The mean thickness of reepithelialized donor-site epidermis (0.13 +/- 0.04 mm, n = 30) was found to be twice the thickness of virgin epidermis from the same sites (0.06 +/- 0.02 mm, n = 38, p < 0.001). Thirty-six grafts harvested with dermatomes set to cut 8/1000 inch (0.20 mm) deep ranged from 0.12 to 0.42 mm thick, with only eight of these grafts measuring within +/-10 percent of the desired thickness setting. Before donor dressing separation, Xeroform and Jelonet dressings were judged to be more comfortable by nine patients and one patient, respectively, whereas no difference was detected by six patients. The authors now use Xeroform as the preferred donor dressing.     

仿生技术构建小口径人造血管

目的：研究以改性猪小肠粘膜下层组织(SIS)为支架,利用仿生技术构建小口径人造血管的可行性。方法：自犬隐动脉分离出血管内皮细胞和平滑肌细胞,与胶原蛋白凝胶均匀混合,分别种植于改性SIS膜表面,制成3 mm 仿生三层人造血管为实验组;制成单层人造血管为对照组,分别植入修复15例犬双侧股动脉缺损,术后进行彩超、组织学检测和电镜检测鉴定。结果：植入12周,14个仿生人造血管保持通畅,通畅率93.3%,有血管样生物结构形成,管腔内壁有完整的内皮覆盖,管壁中层见大量平滑肌细胞;对照组通畅率60%,有少许内皮细胞覆盖。结论：仿生小口径人造血管具有良好的血液相容性,并能在体内保持良好通畅性, 修复动脉缺损效果满意。     

Treatment of midfacial defects using prostheses supported by ITI dental implants

The purpose of this study was to evaluate retrospectively the use of ITI dental implants used for anchoring facial prostheses in the restorative treatment of midface defects. The authors analyzed the clinical data of 26 patients with orbital defects (n = 11), orbitonasal defects (n = 4), orbitonasomaxillary defects (n = 3), and nasal defects (n = 8). Data included age, sex, primary disease, implant position, implant length, implant failure, prosthetic attachment, radiation therapy, and peri-implant skin reactions. Follow-up was at 1, 3, 6, and 12 months and then on a yearly basis. The authors noted the status of healing and complications, if any. In total, 62 implants were placed as follows: 27 (43.5 percent) for orbital prostheses, 12 (19.4 percent) for orbitonasal prostheses, 14 (22.6 percent) for orbitonasomaxillary prostheses, and nine (14.5 percent) for nasal prostheses. Thirty-eight implants (61.3 percent) were placed in previously irradiated areas in 18 patients (69.2 percent). Mild skin reactions together with mild accumulation of sebaceous crusting around implants were recorded in 14.2 percent of the skin observations. No patient experienced severe inflammation requiring administration of systemic antibiotics or surgical revision. Implant success was 100 percent in both irradiated and nonirradiated patients. In conclusion, ITI dental implants result in a high rate of success in retaining midface prostheses and offer good stability and aesthetic satisfaction.