Nonautogenous Grafts Research Articles

Sustained delivery of the angiogenic QK peptide through the use of polyglutamate domains to control peptide release from bone graft materials.

Angiogenesis plays a pivotal role in tissue regeneration following bone-grafting procedures; however, nonautogenous graft materials typically lack critical angiogenic growth factors. While much research has focused on modifying grafts with angiogenic factors, controlled delivery of these molecules remains a challenge. The current study describes a method for sustained delivery of an angiogenic peptide from hydroxyapatite (HA), a common alloplast material. Specifically, VEGF-derived "QK" peptides were synthesized with polyglutamate domains containing varying numbers of glutamates. The rate of peptide release from HA inversely correlated with glutamate number, with diglutamate-QK (E2-QK) released first, followed by tetraglutamate-QK (E4-QK), and finally, heptaglutamate-QK (E7-QK). By coating HA with a mixture of these peptides, termed, PGM-QK (polyglutamate-modified mixture), sequential peptide release was achieved, enabling gradient QK delivery. To evaluate bioactivity, HA disks were coated with PGM-QK and then placed in fresh media for 6 days. Media containing the released peptides was collected at varying time intervals and placed on human umbilical vein endothelial cells (HUVECs). Cells were evaluated for activation of angiogenic signaling pathways (ERK and Akt) and cell migration. Results showed that QK peptides were continuously released over the 6-day interval, and maintained their capacity to activate HUVECs. These findings point to a new approach for gradient delivery of an angiogenic stimulus.

Five-Year Patency Rates for Heparin-Bonded Expanded Polytetrafluoroethylene Femoropopliteal Bypass Grafts vs ePTFE Grafts Without Heparin

Expanded polytetrafluoroethylene (ePTFE) grafts have become the dominant nonautogenous grafts for infrainguinal arterial reconstructions to both the above-knee (AK) and below-knee (BK) popliteal arteries. In recent years, heparin bonding to the luminal surface has been used as a possible adjunctive method to improve patency of these grafts. Previous publications dealing with ePTFE have demonstrated that long-term patency results are necessary in order to fully evaluate the clinical utility of these grafts. Accordingly, we have retrospectively evaluated a prospective experience with HePTFE and compared the results with a previous experience with standard ePTFE (SePTFE) in order to compare 5-year patency for both AK and BK grafts. Before August 2007, all nonautogenous femoropopliteal bypasses performed by our four-surgeon group were constructed using 6-mm SePTFE manufactured by the Atrium Medical Corporation (Nashua, NH) or W. L. Gore & Associates (Flagstaff, Ariz). Subsequently, all such bypasses were constructed using 6-mm HePTFE (Propaten; W. L. Gore & Associates). There was no change in operative technique during these two time periods. The surgical technique used in all cases was similar for all four surgeons, irrespective of graft material, and did not change during the course of the study. There were 192 AK (87 HePTFE; 105 SePTFE) and 60 (42 HePTFE; 18 SePTFE) BK grafts. Multivariate analysis demonstrated that both varieties of SePTFE (Atrium and Gore) achieved similar patency rates and so results for SePTFE include both grafts from both companies. Overall primary patency for HePTFE was statistically better than SePTFE at years 1e (93.6% vs 84.2%), 2 (79.7% vs 73.8%), 3 (79.7% vs 69.5%), 4 (74.5% vs 59.9%), and 5 (74.5% vs 56.2%). Five-year primary patency was superior for HePTFE AK grafts (85.2% vs 59.3%) Graph #1 and for HePTFE BK grafts (59.6% vs 43.3%) Graph #2.Variables associated with loss of patency for ePTFE and HePTFE were isolated popliteal artery (HR, 3.11), chronic limb ischemia (HR 2.4), failure to use clopidogrel (HR, 1.93), and young age (HR, 0.95). The Gore Propaten graft offers significantly improved long-term patency over standard ePTFE. On the basis of these data, it would appear that this material should be the graft of choice for bypasses to the popliteal artery when saphenous vein is unavailable or inappropriate. The data also suggest that HePTFE Propaten may be a suitable first-line graft for AK femoropopliteal bypasses in older patients on clopidogrel with good runoff arteries, thus saving the saphenous vein for a subsequent bypass.Fig 2View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Arteriyovenöz fistül anevrizma revizyonlarında anevrizmorafi ve plikasyon: Klinik deneyimlerimiz

Background: This study aims to investigate the reliability of aneurysmorrhaphy method which allows distal dialysis access through conduit obtained from the native tissue of the patient without using an autogenous and non-autogenous grafts. Methods: Between August 2007 and February 2013, 14 patients (6 males, 8 females; mean age 54.2 years; range 28 to 74 years) with arteriovenous fistula aneurysm who underwent aneurysmorrhaphy in our clinic were retrospectively analyzed. Results: No fistula loss was seen in the early period. Only two patients (14%) needed temporary catheterization for shorter than two weeks. The mean follow-up was 13.8 months (range, 2 to 36 months). One patient died due to myocardial infarction during follow-up. Two patients (14.3%) had steal syndrome at three days and four months following the intervention. Primary fistula patency was 71.4%, while secondary fistula patency was 85.7%. Conclusion: Aneurysmorrhaphy does not require synthetic graft and saphenous vein use in the revisions of arteriovenous fistula aneurysm. It also reduces the proximal migration of the shunt and catheter need. We believe that aneurysmorrhaphy, as a safe and satisfactory technique, should be adopted widely.

Tooth Movement out of the Bony Wall Using Augmented Corticotomy with Nonautogenous Graft Materials for Bone Regeneration

This prospective randomized split-mouth study was performed to compare the effects of augmented corticotomy with those of different nonautogenous bone graft materials combined with orthodontic tooth movement in dogs. Decortication was performed on the buccal bone surface of 6 male beagle dogs that were randomly assigned to receive grafts of deproteinized bovine bone mineral, irradiated cortical bone, or synthetic bone. Immediate orthodontic force was applied to the second and third premolars for buccal tipping for 6 weeks. The pocket depth and width of keratinized tissue (WKT) were measured. Histologic and histomorphometric analyses were performed. The probing depth, WKT, and ratio of the area of new bone to that of total bone on the buccal side were not significantly different between groups. All groups had considerable new bone formation on the pressure side. New bone formation on the buccal side and buccal plate formation in the coronal direction along the root surfaces were induced by the bone-derived and PDL-derived mesenchymal matrix, respectively. The angular change between groups was significantly different (P < 0.001). Augmented corticotomy using nonautogenous graft materials facilitated tooth movement without fenestrations and accelerated new bone formation on the pressure side.

Clinical Efficacy of Growth Factors to Enhance Tissue Repair in Oral and Maxillofacial Reconstruction: A Systematic Review

Provide a comprehensive overview on the clinical use and the efficacy of growth factors in different reconstructive procedures in the oral maxillofacial area. A systematic review of the literature on the clinical use of human and human recombinant growth factors in oral maxillofacial reconstruction has been performed. The use of autogenous growth factors in platelet concentrates (PCs) has shown to be beneficial in the treatment of intrabony pockets at a reasonable level of evidence by improving probing depth and clinical attachment levels as well as linear bone fill within the limits of the observation periods. The application in conjunction with non-autogenous graft materials has been superior to the use of PCs only or grafting materials alone. No benefits have been shown for the use of PCs in recession treatment. When used in furcation treatment, probing depth, clinical attachment level and linear bone fill have been reported to improve significantly, however, without clinical benefit. No benefit for the final outcome could be shown for the use of PCs neither in sinus lift procedures nor in lateral / vertical crest augmentations. The use of human recombinant growth factors has been so far limited almost exclusively to rhPDGF-BB and rhBMPs (BMP-2, BMP-7 and GDF-5). The use of rhPDGF in the treatment of intrabony pockets has shown a reliable increase in linear bone fill but weaker evidence for permanent improvements of clinical attachment level. So far there is no evidence to support the use in recession treatment, sinus lift procedures and socket healing as well as lateral / vertical augmentations of the alveolar crest. rhBMPs have shown to be effective in enhancing bone formation in socket healing (rhBMP-2) and sinus lift procedures (rhBMP-2 and GDF-5). No controlled studies are available for the use in mandibular segmental repair. Successful reports on this application appear to be limited to primary reconstruction after ablative surgery for benign pathology with preservation of the periosteum. Evidence of clinical efficacy of growth factors in reconstructive procedures in the oral and maxillofacial area is limited.

Advanced Biomaterials and Technologies in Implantology

Advanced Biomaterials and Technologies in Implantology

Trommelfellrekonstruktion mit nicht-autogenen Transplantaten und alloplastischen Materialien

Autogenous tissue has been the grafting material of choice in reconstruction of permanent tympanic membrane perforations. Although donor site complications are infrequent and morbidity from such harvest is usually quite low, there are nevertheless risks associated with additional incisions when autogenous tissue is used. In addition, in patients who have undergone several grafting attempts, there may be no suitable grafting material in the vicinity of the operative field. Several alternatives to native grafting material have recently become available, which have shown similar success rates of perforation closure as well as postoperative audiologic results. This article gives an overview on these non-autogenous grafts and alloplastic materials.

Implant survival rates after maxillary sinus augmentation

Implant therapy in the atrophic posterior maxilla becomes challenging in the presence of reduced maxillary bone height. Sinus augmentation can be performed for resolving this condition prior to implant placement. The aim of this article was therefore to evaluate implant survival rates in the grafted sinus taking into account the influence of the implant surface, graft material, and implant placement timing. A systematic review of the literature was performed. Articles retrieved from electronic databases were screened using specific inclusion criteria, and data extracted were divided according to: graft material (autogenous, non-autogenous, composite graft), implant surface (machined or textured), and implant placement (simultaneous with grafting or delayed). Fifty-nine articles were included. Survival rates for implants placed in grafts made of bone substitutes alone and grafts of composite material were slightly better than the survival rates for implants placed in 100% autogenous grafts. Over 90% of implants associated with non-autogenous grafts had a textured surface. Textured surfaces achieved better outcomes compared with machined surfaces, and this was independent of the graft material. Simultaneous and delayed procedures had similar outcomes. It may be concluded that bone substitutes can be successfully used for sinus augmentation, reducing donor-site morbidity. Long-term studies are needed to confirm the performance of non-autogenous grafts. The use of implants with a textured surface may improve the outcome in any graft type.

Arteriovenous Fistulae vs. Arteriovenous Grafts: A Retrospective Review of 1,700 Consecutive Vascular access Cases

Vascular access (VA) procedures are rapidly becoming the most prevalent surgery in the United States. It is estimated that there will be over 500,000 VA procedures done this year. Previously, surgeons in the US were attempting many more non-autogenous grafts than autogenous fistulae. In recent years, there has been a great push called 'Fistula First' to promote arteriovenous fistulae (AVF) as the first line of treatment vs. nonautogenous grafts. The goal of this investigation is to determine if too many fistulae are now being performed without attention to specific patient profiles. A retrospective review of 1700 consecutive cases was performed by one surgeon at one institution between 1997 and 2005. Patients were categorized by demographics, co-morbidities, previous access procedures, access location, and type of graft. Patency was calculated. Kaplan-Meier, Cox regression and the Log Rank Test were used to analyze data. Access endpoints and complications were also documented. The study reviewed 1700 procedures. The median age was 52 (60.2% male) with 58.7% fistulae and 41.3% grafts. Median patency time was 10 months, with no statistically significant difference between access types. There was no significant difference in length of patency when comparing upper arm (70.1%), lower arm (24.5%) and thigh (5.4%). Graft infection rate was 9.5% and fistula infection rate was 0.9% (p<0.001). The overall infection rate was 4.5%, and decreased patency significantly (4 vs. 11 months). Thrombosis occurred in 24.7% of grafts and 9.0% of fistulae. Thrombosed grafts had better salvage rates (8 vs. 4 months, p<0.001). The data showed diabetes, HTN and HIV have no overall impact on patency. AVF and grafts are both useful in providing VA for patients requiring hemodialysis. Our data shows that grafts are equivalent in long-term patency. Therefore, it is apparent in those patients who are not candidates for an AV fistula; an AV graft for VA should be placed.

Balancing Fistula First With Catheters Last

The success of Fistula First nationwide has been accompanied by an unplanned increase in hemodialysis catheters. Complications related to prolonged hemodialysis catheter use include increased morbidity, mortality, and cost. We hypothesize that the national focus on increasing fistulas may have inadvertently diverted attention away from initiatives to decrease dependence on hemodialysis catheters. Based on a synthesis of guidelines, reviews, published evidence, and the authors' opinions, we propose that the national vascular access initiative be revised to have a dual goal of Fistula First and "Catheters Last." These goals are not mutually exclusive, but rather complementary. We recommend a systematic refocus on interventions that not only increase fistulas, but help avoid extended catheter use. Clearly, the ideal practice for hemodialysis vascular access remains early placement of fistulas with enough maturation time such that they can be used for initiating long-term hemodialysis therapy when the need arises. To effect this change, a reimbursement policy covering the costs associated with permanent access placement before the need for dialysis is essential. Individualized patient management strategies may consider such innovative approaches as initiating patients on peritoneal dialysis therapy or using nonautogenous grafts as bridge accesses in lieu of catheters. For patients who are dialyzing using catheters, immediate active planning for permanent access placement and removal of the catheter is necessary. In the same vein as Fistula First, the renal community should once again be galvanized in working together toward controlling the catheter epidemic in our dialysis population.

The Fate of Folded and Unfolded Dermal Grafts: A Histopathologic and Structural Study of Rabbits

Currently, both autogenous and nonautogenous materials are used to treat contour deformities. Autogenous grafts are preferable to nonautogenous grafts because they cause less reaction and are both inexpensive and easy to obtain. Currently, however, no consensus exists on an ideal autogenous graft. As autogenous materials, dermal grafts can be obtained from scar tissue, allowing simultaneous revision of scars, quicker vascularization than with other autogenous tissues, and a very short immobilization for their stabilization (i.e., they interact with surrounding tissues). The operation can be performed with the patient under local anesthesia, providing regular contours easily. Alternative techniques are needed to increase the viability and mass effects of autogenous grafts in the long term. With this as the objective, folded dermal grafts were used to increase the mass effects of dermal grafts. The current study compared long-term histopathologic and structural changes in unfolded and folded dermal autogenous grafts used for correction of soft tissue contour deformities. Thicknesses and histopathologic changes of the unfolded and folded dermal autogenous grafts were evaluated 6 and 12 months after placement of the grafts in the abdomens of 10 rabbits. Both the authors' observations and histopathologic examinations showed that the folded dermis caused a more severe granulomatous reaction and fibrosis. Graft thicknesses considerably increased in the first 6 months, but then almost leveled off in the following months. Increased fibrosis in the folded grafts had a masslike effect, which was preserved in the long term, suggesting that folded dermal grafts can be used clinically.

A Changing Pattern of Infection After Major Vascular Reconstructions

Wound and graft infection can occur in more than 40% of patients undergoing vascular reconstructions for peripheral arterial disease (PAD). A recent increase in the frequency and severity of infections, as well as a change in the microorganisms recovered, led us to undertake a retrospective case-controlled study of wound/graft infections at this institution. The medical records of all patients undergoing vascular reconstruction for PAD during the previous 36 months were reviewed. Patient demographics, graft location and conduit, infection location, causative microorganisms, and factors potentially associated with development of infection were recorded. Infections were classified according to a modification of the CDC criteria into superficial incisional, deep incisional, or involving the graft (body only, anastomosis without disruption, or anastomosis with disruption). Univariate and multivariate regression analyses were used to identify factors associated with the development of infection. Four hundred ten (84 aortic, 41 extraanatomic, and 285 infrainguinal) revascularization procedures were performed in 217 men and 193 women with a mean age of 62 years (range 43-88). The infection rate for the entire group was 11.0% (45/410). Eighty percent (36/45) occurred after infrainguinal reconstructions and 64% (29/45) of the infections involved the groin incision. Direct involvement of the graft occurred in 67% (30/45), and 27% (12/45) presented with anastomotic disruption. Of the infrainguinal infections, in situ and prosthetic reconstructions were associated with a significantly higher rate of infection than reversed vein grafts tunneled anatomically (p <0.001, chi-square analysis). Patients with nonautogenous grafts (24 expanded polytetrafluoroethylene and 2 bovine) presented with more advanced infections involving the graft (20/26 procedures) and were more likely to present with anastomotic disruption (11/26). Staphylococcus aureus was isolated in the majority of infections (64%) and in all cases involving graft disruption. Multivariate regression analysis identified the following factors associated with development of infection: previous hospitalization (p = 0.03), a younger age (p = 0.047), and the presence of a groin incision (p = 0.04). Twenty-five percent of graft infections resulted in major amputation, and 11% of patients with graft infection died as a result. The incidence, morbidity, and mortality of infections in vascular reconstructions for PAD are increasing dramatically, particularly in infrainguinal reconstructions involving groin incisions. Perioperative antibiotic selection should be modified to include coverage for all Staphylococcal subspecies and hospitalization before surgical procedures should be avoided.

Differential mechanisms of failure of autogenous and non-autogenous bypass conduits: an assessment following successful graft thrombolysis

The advent of graft thrombolysis has provided an objective means for evaluating the etiology of graft occlusion. Over a 10-year period, intra-arterial urokinase (102 cases) or streptokinase (seven cases) was used in 109 infrainguinal conduits (30 autogenous and 79 non-autogenous) that failed 30 days or more after implantantion. Thrombolysis was not achieved in 19 additional graft occlusions; these cases were excluded from study because of an inability to define the mechanism of failure. Non-invasive laboratory data were available within 6 months of graft occlusion in 82 (75%) of the cases, with Doppler segmental studies in 80 cases (73%) and duplex ultrasonography studies in 39 cases (36%). Pre-failure non-invasive laboratory abnormalities were detected more frequently in autogenous grafts (21 of 24 patients, 88%), while non-autogenous grafts usually occluded without prior hemodynamic change (11 of 58 patients had abnormalities, 19%) ( P<0.001). Thrombolysis uncovered anatomic defects responsible for thombosis in 27 (90%) of 30 autogenous grafts compared with only 32 (41%) of non-autogenous conduits ( P<0.001). The most common lesions underlying autogenous graft failure comprised stenoses within the body of the graft (11 cases, 37%), while the most common lesions in failed non-autogenous grafts appeared to be stenoses at an anastomosis (21 cases, 27%). Thus, the mechanisms underlying the late failure of autogenous and non-autogenous grafts differ markedly; autogenous grafts most commonly fall as a result of the gradual development of lesions intrinsic to the graft, while non-autogenous grafts fail precipitously, presumably as a result of some non-anatomic mechanism.

Differential Mechanisms of Failure of Autogenous and Non-Autogenous Bypass Conduits: An Assessment Following Successful Graft Thrombolysis

The advent of graft thrombolysis has provided an objective means for evaluating the etiology of graft occlusion. Over a 10-year period, intra-arterial urokinase (102 cases) or streptokinase (seven cases) was used in 109 infrainguinal conduits (30 autogenous and 79 non-autogenous) that failed 30 days or more after implantantion. Thrombolysis was not achieved in 19 additional graft occlusions; these cases were excluded from study because of an inability to define the mechanism of failure. Non-invasive laboratory data were available within 6 months of graft occlusion in 82 (75%) of the cases, with Doppler segmental studies in 80 cases (73%) and duplex ultrasonography studies in 39 cases (36%). Pre-failure non-invasive laboratory abnormalities were detected more frequently in autogenous grafts (21 of 24 patients, 88%), while non-autogenous grafts usually occluded without prior hemodynamic change (11 of 58 patients had abnormalities, 19%) (P&lt; 0.001). Thrombolysis uncovered anatomic defects responsible for thombosis in 27 (90%) of 30 autogenous grafts compared with only 32 (41%) of non-autogenous conduits (P&lt; 0.001). The most common lesions underlying autogenous graft failure comprised stenoses within the body of the graft (11 cases, 37%), while the most common lesions in failed non-autogenous grafts appeared to be stenoses at an anastomosis (21 cases, 27%). Thus, the mechanisms underlying the late failure of autogenous and non-autogenous grafts differ markedly; autogenous grafts most commonly fail as a result of the gradual development of lesions intrinsic to the graft, while non-autogenous grafts fail precipitously, presumably as a result of some non-anatomic mechanism.

Use of Vicryl (Polyglactin-910) Mesh Implant for Correcting Enophthalmos and Hypo-ophthalmos A Study of 16 Patients

Vicryl mesh (polyglactin-910) implants were used to reconstruct the orbital floor to correct enophthalmos or hypo-ophthalmos (globe ptosis) in 16 patients. The main advantages of Vicryl mesh over other alloplastic implants is that (a) it is absorbed by host tissue, and, once absorbed, it will not cause long-term complications; (b) it is layered and is cut from folded sheets into the appropriate size, shape, and thickness for the treatment of enophthalmos or hypo-ophthalmos; and (c) it is soft and pliable and, therefore, is unlikely to erode orbital structures. We followed all patients for a minimum period of 6 months after surgery and observed no significant adverse reactions to the mesh; 15 of the patients had good surgical results with a mean improvement of 1.4 mm in enophthalmos and 0.6 mm in hypo-ophthalmos. After surgery, one patient with combined medial wall and floor fractures developed enophthalmos that was 2 mm more severe than the degree of preoperative enophthalmos. Vicryl mesh should be considered an alternative to both nonautogenous implants and autogenous grafts in orbital floor fracture repair especially for correction of mild and possibly moderate degrees of enophthalmos and hypo-ophthalmos.

Histomorphologic Evaluation of Scleral Grafts in Experimental Bony Defects

This study was undertaken in order to evaluate and compare the effectiveness and fate of the nonautogenous scleral graft in relation to similar grafts of bone marrow and epithelium-free connective tissue grafts from the palate. One hundred round osseous defects 2 mm in diameter, were surgically created in the calveria of 25 rats. Three defects in each animal were filled with the various graft materials obtained from isogenic rats sacrificed at the time of preparation of the bony defects. The fourth defect was left empty as a control. The animals were sacrificed at varying periods of time up to 150 days. Histomorphologic evaluation of the graft sites demonstrated the following: (a) Scleral grafts had effected a functionally adequate repair, without apparent histopathologic changes. (b) Fresh bone marrow provided the greatest osteogenic activity when used as a graft implant. The sclera had an insignificant osteogenic activity when used as a graft implant. The sclera had an insignificant osteogenic potential. (c) Epithelium-free connective tissue was the least effective, both as an osteogenic or functionally adequate graft.